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Superalloy

A superalloy, or high-performance alloy, is an alloy with the ability to operate at a high fraction of its melting point. Key characteristics of a superalloy include mechanical strength, thermal creep deformation resistance, surface stability, and corrosion and oxidation resistance.

The crystal structure is typically face-centered cubic (FCC) austenitic. Examples of such alloys are Hastelloy, Inconel, Waspaloy, Rene alloys, Incoloy, MP98T, TMS alloys, and CMSX single crystal alloys.

Superalloy development relies on chemical and process innovations. Superalloys develop high temperature strength through solid solution strengthening and precipitation strengthening from secondary phase precipitates such as gamma prime and carbides. Oxidation or corrosion resistance is provided by elements such as aluminium and chromium. Superalloys are often cast as a single crystal in order to eliminate grain boundaries, which decrease creep resistance (even though they may provide strength at low temperatures).

The primary application for such alloys is in aerospace and marine turbine engines. Creep is typically the lifetime-limiting factor in gas turbine blades.

Superalloys have made much of very-high-temperature engineering technology possible.

Chemical development
Because these alloys are intended for high temperature applications their creep and oxidation resistance are of primary importance. Nickel (Ni)-based superalloys are the material of choice for these applications because of their unique γ' precipitates. The properties of these superalloys can be tailored to a certain extent through the addition of various other elements, common or exotic, including not only metals, but also metalloids and nonmetals; chromium, iron, cobalt, molybdenum, tungsten, tantalum, aluminium, titanium, zirconium, niobium, rhenium, yttrium, vanadium, carbon, boron or hafnium are some examples of the alloying additions used. Each addition serves a particular purpose in optimizing properties.

Creep resistance is dependent, in part, on slowing the speed of dislocation motion within a crystal structure. In modern Ni-based superalloys, the γ'-Ni3(Al,Ti) phase acts as a barrier to dislocation. For this reason, this γ;' intermetallic phase, when present in high volume fractions, increases the strength of these alloys due to its ordered nature and high coherency with the γ matrix. The chemical additions of aluminum and titanium promote the creation of the γ' phase. The γ' phase size can be precisely controlled by careful precipitation strengthening heat treatments. Many superalloys are produced using a two-phase heat treatment that creates a dispersion of cuboidal γ' particles known as the primary phase, with a fine dispersion between these known as secondary γ'. In order to improve the oxidation resistance of these alloys, Al, Cr, B, and Y are added. The Al and Cr form oxide layers that passivate the surface and protect the superalloy from further oxidation while B and Y are used to improve the adhesion of this oxide scale to the substrate. Cr, Fe, Co, Mo and Re all preferentially partition to the γ matrix while Al, Ti, Nb, Ta, and V preferentially partition to the γ' precipitates and solid solution strengthen the matrix and precipitates respectively. In addition to solid solution strengthening, if grain boundaries are present, certain elements are chosen for grain boundary strengthening. B and Zr tend to segregate to the grain boundaries which reduces the grain boundary energy and results in better grain boundary cohesion and ductility. Another form of grain boundary strengthening is achieved through the addition of C and a carbide former, such as Cr, Mo, W, Nb, Ta, Ti, or Hf, which drives precipitation of carbides at grain boundaries and thereby reduces grain boundary sliding.

Phase formation
Adding elements is usually helpful because of solid solution strengthening, but can result in unwanted precipitation. Precipitates can be classified as geometrically close-packed (GCP), topologically close-packed (TCP), or carbides. GCP phases usually benefit mechanical properties, but TCP phases are often deleterious. Because TCP phases are not truly close packed, they have few slip systems and are brittle. Also they "scavenge" elements from GCP phases. Many elements that are good for forming γ' or have great solid solution strengthening may precipitate TCPs. The proper balance promotes GCPs while avoiding TCPs.

TCP phase formation areas are weak because they:

 * have inherently poor mechanical properties
 * are incoherent with the γ matrix
 * are surrounded by a "depletion zone" where there is no γ'
 * usually form sharp plate or needle-like morphologies which nucleate cracks

The main GCP phase is γ'. Almost all superalloys are Ni-based because of this phase. γ' is an ordered L1$3$ (pronounced L-one-two), which means it has a certain atom on the face of the unit cell, and a certain atom on the corners of the unit cell. Ni-based superalloys usually present Ni on the faces and Ti or Al on the corners.

Another "good" GCP phase is γ ''. It is also coherent with γ, but it dissolves at high temperatures.

History
The United States became interested in gas turbine development around 1905. From 1910-1915, austenitic ( γ phase) stainless steels were developed to survive high temperatures in gas turbines. By 1929, 80Ni-20Cr alloy was the norm, with small additions of Ti and Al. Although early metallurgists did not know it yet, they were forming small γ' precipitates in Ni-based superalloys. These alloys quickly surpassed Fe- and Co-based superalloys, which were strengthened by carbides and solid solution strengthening.

Although Cr was great for protecting the alloys from oxidation and corrosion up to 700 °C, metallurgists began decreasing Cr in favor of Al, which had oxidation resistance at much higher temperatures. The lack of Cr caused issues with hot corrosion, so coatings needed to be developed.

Around 1950, vacuum melting became commercialized, which allowed metallurgists to create higher purity alloys with more precise composition.

In the 60s and 70s, metallurgists changed focus from alloy chemistry to alloy processing. Directional solidification was developed to allow columnar or even single-crystal turbine blades. Oxide dispersion strengthening could obtain very fine grains and superplasticity.

Phases

 * Gamma (γ): This phase composes the matrix of Ni-based superalloy. It is a solid solution fcc austenitic phase of the alloying elements. The alloying elements most found in commercial Ni-based alloys are, C, Cr, Mo, W, Nb, Fe, Ti, Al, V, and Ta. During the formation of these materials, as they cool from the melt, carbides precipitate, and at even lower temperatures γ' phase precipitates.
 * Gamma prime (γ'): This phase constitutes the precipitate used to strengthen the alloy. It is an intermetallic phase based on Ni3(Ti,Al) which have an ordered FCC L12 structure. The γ' phase is coherent with the matrix of the superalloy having a lattice parameter that varies by around 0.5%. Ni3(Ti,Al) are ordered systems with Ni atoms at the cube faces and either Al or Ti atoms at the cube edges. As particles of γ' precipitates aggregate, they decrease their energy states by aligning along the directions forming cuboidal structures. This phase has a window of instability between 600 °C and 850 °C, inside of which γ' will transform into the HCP η phase. For applications at temperatures below 650 °C, the γ" phase can be utilized for strengthening.

 * Gamma double prime (γ"): This phase typically is Ni3Nb or Ni3V and is used to strengthen Ni-based superalloys at lower temperatures (<650 °C) relative to γ'. The crystal structure of γ" is body-centered tetragonal (BCT), and the phase precipitates as 60 nm by 10 nm discs with the (001) planes in γ" parallel to the {001} family in γ. These anisotropic discs form as a result of lattice mismatch between the BCT precipitate and the FCC matrix. This lattice mismatch leads to high coherency strains which, together with order hardening, are the primary strengthening mechanisms. The γ" phase is unstable above approximately 650 °C.
 * Carbide phases: Carbide formation is usually deleterious although in Ni-based superalloys they are used to stabilize the structure of the material against deformation at high temperatures. Carbides form at the grain boundaries, inhibiting grain boundary motion.
 * Topologically close-packed (TCP) phases: The term "TCP phase" refers to any member of a family of phases (including the σ phase, the χ phase, the μ phase, and the Laves phase), which are not atomically close-packed but possess some close-packed planes with HCP stacking. TCP phases tend to be highly brittle and deplete the γ matrix of strengthening, solid solution refractory elements (including Cr, Co, W, and Mo). These phases form as a result of kinetics after long periods of time (thousands of hours) at high temperatures (>750 °C).

Co-based
Co-based superalloys depend on carbide precipitation and solid solution strengthening for mechanical properties. While these strengthening mechanisms are inferior to gamma prime (γ') precipitation strengthening, cobalt has a higher melting point than nickel and has superior hot corrosion resistance and thermal fatigue. As a result, carbide-strengthened Co-based superalloys are used in lower stress, higher temperature applications such as stationary vanes in gas turbines.

Co's γ/γ' microstructure was rediscovered and published in 2006 by Sato et al. That γ' phase was Co3(Al, W). Mo, Ti, Nb, V, and Ta partition to the γ' phase, while Fe, Mn, and Cr partition to the matrix γ.

The next family of Co-based superalloys was discovered in 2015 by Makineni et al. This family has a similar γ/γ' microstructure, but is W-free and has a γ' phase of Co3(Al,Mo,Nb). Since W is heavy, its elimination makes Co-based alloys increasingly viable in turbines for aircraft, where low density is especially valued.

The most recently discovered family of superalloys was computationally predicted by Nyshadham et al. in 2017, and demonstrated by Reyes Tirado et al. in 2018. This γ' phase is W free and has the composition Co3(Nb,V) and Co3(Ta,V).

Phases

 * Gamma (γ): This is the matrix phase. While Co-based superalloys are less-used commercially, alloying elements include C, Cr, W, Ni, Ti, Al, Ir, and Ta. As in stainless steels, Chromium is used (occasionally up to 20 wt.%) to improve resistance to oxidation and corrosion via the formation of a Cr2O3 passive layer, which is critical for use in gas turbines, but also provides solid-solution strengthening due to the mismatch in the atomic radii of Co and Cr, and precipitation hardening due to the formation of MC-type carbides.
 * Gamma Prime (γ'): Constitutes the precipitate used to strengthen the alloy. It is usually close-packed with a L12 structure of Co3Ti or FCC Co3Ta, though both W and Al integrate into these cuboidal precipitates. Ta, Nb, and Ti integrate into the γ' phase and are stabilize it at high temperatures.
 * Carbide Phases: Carbides strengthen the alloy through precipitation hardening but decrease low-temperature ductility.
 * Topologically Close-Packed (TCP) phases may appear in some Co-based superalloys, but embrittle the alloy and are thus undesirable.

Fe-based
Steel superalloys are of interest because some present creep and oxidation resistance similar to Ni-based superalloys, at far less cost.

Gamma (γ): Fe-based alloys feature a matrix phase of austenite iron (FCC). Alloying elements include: Al, B, C, Co, Cr, Mo, Ni, Nb, Si, Ti, W, and Y. Al (oxidation benefits) must be kept at low weight fractions (wt.%) because Al stabilizes a ferritic (BCC) primary phase matrix, which is undesirable, as it is inferior to the high temperature strength exhibited by an austenitic (FCC) primary phase matrix.

Gamma-prime (γ'): This phase is introduced as precipitates to strengthen the alloy. γ'-Ni3Al precipitates can be introduced with the proper balance of Al, Ni, Nb, and Ti additions.

Microstructure
The two major types of austenitic stainless steels are characterized by the oxide layer that forms on the steel surface: either chromia-forming or alumina-forming. Cr-forming stainless steel is the most common type. However, Cr-forming steels do not exhibit high creep resistance at high temperatures, especially in environments with water vapor. Exposure to water vapor at high temperatures can increase internal oxidation in Cr-forming alloys and rapid formation of volatile Cr (oxy)hydroxides, both of which can reduce durability and lifetime.

Al-forming austenitic stainless steels feature a single-phase matrix of austenite iron (FCC) with an Al-oxide at the surface of the steel. Al is more thermodynamically stable in oxygen than Cr. More commonly, however, precipitate phases are introduced to increase strength and creep resistance. In Al-forming steels, NiAl precipitates are introduced to act as Al reservoirs to maintain the protective alumina layer. In addition, Nb and Cr additions help form and stabilize Al by increasing precipitate volume fractions of NiAl.

At least 5 grades of alumina-forming austenitic (AFA) alloys, with different operating temperatures at oxidation in air + 10% water vapor have been realized: Operating temperatures with oxidation in air and no water vapor are expected to be higher. In addition, an AFA superalloy grade exhibits creep strength approaching that of nickel alloy UNS N06617.
 * AFA Grade: (50-60)Fe-(20-25)Ni-(14-15)Cr-(2.5-3.5)Al-(1-3)Nb wt.% base
 * 750-800 °C operating temperatures at oxidation in air + 10% water vapor
 * Low Nickel AFA Grade: 63Fe-12Ni-14Cr-2.5Al-0.6Nb-5Mn3Cu wt.% base
 * 650 °C operating temperatures at oxidation in air + 10% water vapor
 * High Performance AFA Grade: (45-55)Fe-(25-30)Ni-(14-15)Cr(3.5-4.5)Al-(1-3)Nb-(0.02-0.1)Hf/Y wt.% base
 * 850-900 °C operating temperatures at oxidation in air + 10% water vapor
 * Cast AFA Grade: (35-50)Fe-(25-35)Ni-14Cr-(3.5-4)Al-1Nb wt.% base
 * 750-1100 °C operating temperatures at oxidation in air + 10% water vapor, depending upon Ni wt.%
 * AFA superalloy (40-50)Fe-(30-35)Ni-(14-19)Cr-(2.5-3.5)Al-3Nb
 * 750-850 °C operating temperatures at oxidation in air + 10% water vapor

Microstructure
In pure Ni3Al phase Al atoms are placed at the vertices of the cubic cell and form sublattice A. Ni atoms are located at centers of the faces and form sublattice B. The phase is not strictly stoichiometric. An excess of vacancies in one of the sublattices may exist, which leads to deviations from stoichiometry. Sublattices A and B of the γ' phase can solute a considerable proportion of other elements. The alloying elements are dissolved in the γ phase. The γ' phase hardens the alloy through the yield strength anomaly. Dislocations dissociate in the γ' phase, leading to the formation of an anti-phase boundary. To give an example, consider a dislocation with a burgers vector of $$\frac{a}{2}\left [ 1 \bar{1} 0 \right ]$$ traveling along a $$\left \{ 1 1 1 \right \}$$ slip plane initially in the γ phase, where it is a perfect dislocation in that FCC structure. Since the γ' phase is primitive cubic instead of FCC due to the substitution of aluminum into the vertices of the unit cell, the perfect burgers vector along that direction in γ' is twice that of γ. For the $$\frac{a}{2}\left [ 1 \bar{1} 0 \right ]$$ dislocation to enter the γ' phase, it will have to create a high energy anti-phase boundary, which will need another such dislocation along the plane to restore order (as the sum of the two dislocations would have the perfect $$a \left [ 1 \bar{1} 0 \right ]$$ burgers vector).

It is thus rather energy prohibitive for the dislocation to enter the γ' phase unless there are two of them in close proximity along the same plane. However, the Peach-Koehler force between identical dislocations along the same plane is repulsive, which makes this a less favorable configuration. One possible mechanism involved one of the dislocations being pinned against the γ' phase while the other dislocation in the γ phase cross-slips into close proximity of the pinned dislocation from another plane, allowing the pair of dislocations to push into the γ' phase.

Furthermore, the burgers vector $$\frac{a}{2}\left \langle 110 \right \rangle$$ family of dislocations are likely to decompose into partial dislocations in this alloy due to its low stacking fault energy, such as dislocations with burgers vector of the $$\frac{a}{6}\left \langle 211 \right \rangle$$ family (Shockley partial dislocations). The stacking faults between these partial dislocations can further provide another obstacle to the movement of other dislocations, further contributing to the strength of the material. There are also more slip systems that can be involved beyond the $$\left \{ 1 1 1 \right \}$$ slip plane and $$\left \langle 110 \right \rangle$$ slip direction.

At elevated temperature, the free energy associated with the anti-phase boundary (APB) is considerably reduced if it lies on a particular plane, which by coincidence is not a permitted slip plane. One set of partial dislocations bounding the APB cross-slips so that the APB lies on the low-energy plane, and, since this low-energy plane is not a permitted slip plane, the dissociated dislocation is effectively locked. By this mechanism, the yield strength of γ' phase Ni3Al increases with temperature up to about 1000 °C.

Initial material selection for blade applications in gas turbine engines included alloys like the Nimonic series alloys in the 1940s. The early Nimonic series incorporated γ' Ni3(Al,Ti) precipitates in a γ matrix, as well as various metal-carbon carbides (e.g. Cr23C6) at the grain boundaries for additional grain boundary strength. Turbine blade components were forged until vacuum induction casting technologies were introduced in the 1950s. This process significantly improved cleanliness, reduced defects, and increased the strength and temperature capability.

Modern superalloys were developed in the 1980s. First generation superalloys incorporated increased Al, Ti, Ta, and Nb content in order to increase the γ' volume fraction. Examples include: PWA1480, René N4 and SRR99. Additionally, the volume fraction of the γ' precipitates increased to about 50–70% with the advent of monocrystal solidification techniques that enable grain boundaries to be entirely eliminated. Because the material contains no grain boundaries, carbides are unnecessary as grain boundary strengthers and were thus eliminated.

Second and third generation superalloys introduce about 3 and 6 weight percent rhenium, for increased temperature capability. Re is a slow diffuser and typically partitions the γ matrix, decreasing the rate of diffusion (and thereby high temperature creep) and improving high temperature performance and increasing service temperatures by 30 °C and 60 °C in second and third generation superalloys, respectively. Re promotes the formation of rafts of the γ' phase (as opposed to cuboidal precipitates). The presence of rafts can decrease creep rate in the power-law regime (controlled by dislocation climb), but can also potentially increase the creep rate if the dominant mechanism is particle shearing. Re tends to promote the formation of brittle TCP phases, which has led to the strategy of reducing Co, W, Mo, and particularly Cr. Later generations of Ni-based superalloys significantly reduced Cr content for this reason, however with the reduction in Cr comes a reduction in oxidation resistance. Advanced coating techniques offset the loss of oxidation resistance accompanying the decreased Cr contents. Examples of second generation superalloys include PWA1484, CMSX-4 and René N5.

Third generation alloys include CMSX-10, and René N6. Fourth, fifth, and sixth generation superalloys incorporate ruthenium additions, making them more expensive than prior Re-containing alloys. The effect of Ru on the promotion of TCP phases is not well-determined. Early reports claimed that Ru decreased the supersaturation of Re in the matrix and thereby diminished the susceptibility to TCP phase formation. Later studies noted an opposite effect. Chen, et al., found that in two alloys differing significantly only in Ru content (USTB-F3 and USTB-F6) that the addition of Ru increased both the partitioning ratio as well as supersaturation in the γ matrix of Cr and Re, and thereby promoted the formation of TCP phases.

The current trend is to avoid very expensive and very heavy elements. An example is Eglin steel, a budget material with compromised temperature range and chemical resistance. It does not contain rhenium or ruthenium and its nickel content is limited. To reduce fabrication costs, it was chemically designed to melt in a ladle (though with improved properties in a vacuum crucible). Conventional welding and casting is possible before heat-treatment. The original purpose was to produce high-performance, inexpensive bomb casings, but the material has proven widely applicable to structural applications, including armor.

Single-crystal superalloys
Single-crystal superalloys (SX or SC superalloys) are formed as a single crystal using a modified version of the directional solidification technique, leaving no grain boundaries. The mechanical properties of most other alloys depend on the presence of grain boundaries, but at high temperatures, they participate in creep and require other mechanisms. In many such alloys, islands of an ordered intermetallic phase sit in a matrix of disordered phase, all with the same crystal lattice. This approximates the dislocation-pinning behavior of grain boundaries, without introducing any amorphous solid into the structure.

Single crystal (SX) superalloys have wide application in the high-pressure turbine section of aero- and industrial gas turbine engines due to the unique combination of properties and performance. Since introduction of single crystal casting technology, SX alloy development has focused on increased temperature capability, and major improvements in alloy performance are associated with rhenium (Re) and ruthenium (Ru).

The creep deformation behavior of superalloy single crystal is strongly temperature-, stress-, orientation- and alloy-dependent. For a single-crystal superalloy, three modes of creep deformation occur under regimes of different temperature and stress: rafting, tertiary, and primary. At low temperature (~750 °C), SX alloys exhibits mostly primary creep behavior. Matan et al. concluded that the extent of primary creep deformation depends strongly on the angle between the tensile axis and the / symmetry boundary. At temperatures above 850 °C, tertiary creep dominates and promotes strain softening behavior. When temperature exceeds 1000 °C, the rafting effect is prevalent where cubic particles transform into flat shapes under tensile stress. The rafts form perpendicular to the tensile axis, since γ phase is transported out of the vertical channels and into the horizontal ones. Reed et al. studied unaxial creep deformation of oriented CMSX-4 single crystal superalloy at 1105 °C and 100 MPa. They reported that rafting is beneficial to creep life since it delays evolution of creep strain. In addition, rafting occurs quickly and suppresses the accumulation of creep strain until a critical strain is reached.

Oxidation
For superalloys operating at high temperatures and exposed to corrosive environments, oxidation behavior is a concern. Oxidation involves chemical reactions of the alloying elements with oxygen to form new oxide phases, generally at the alloy surface. If unmitigated, oxidation can degrade the alloy over time in a variety of ways, including:

 * sequential surface oxidation, cracking, and spalling, eroding the alloy over time
 * surface embrittlement through the introduction of oxide phases, promoting crack formation and fatigue failure
 * depletion of key alloying elements, affecting mechanical properties and possibly compromising performance

Selective oxidation is the primary strategy used to limit these deleterious processes. The ratio of alloying elements promotes formation of a specific oxide phase that then acts as a barrier to further oxidation. Most commonly, aluminum and chromium are used in this role, because they form relatively thin and continuous oxide layers of alumina (Al2O3) and chromia (Cr2O3), respectively. They offer low oxygen diffusivities, effectively halting further oxidation beneath this layer. In the ideal case, oxidation proceeds through two stages. First, transient oxidation involves the conversion of various elements, especially the majority elements (e.g. nickel or cobalt). Transient oxidation proceeds until the selective oxidation of the sacrificial element forms a complete barrier layer.

The protective effect of selective oxidation can be undermined. The continuity of the oxide layer can be compromised by mechanical disruption due to stress or may be disrupted as a result of oxidation kinetics (e.g. if oxygen diffuses too quickly). If the layer is not continuous, its effectiveness as a diffusion barrier to oxygen is compromised. The stability of the oxide layer is strongly influenced by the presence of other minority elements. For example, the addition of boron, silicon, and yttrium to superalloys promotes oxide layer adhesion, reducing spalling and maintaining continuity.

Oxidation is the most basic form of chemical degradation superalloys may experience. More complex corrosion processes are common when operating environments include salts and sulfur compounds, or under chemical conditions that change dramatically over time. These issues are also often addressed through comparable coatings.

Creep
One of the main strengths of superalloys are their superior creep resistant properties when compared to most conventional alloys. To start, 𝛾’-strengthened superalloys have the benefit of requiring dislocations to move in pairs due to the phase creating a high antiphase boundary (APB) energy during dislocation motion. This high APB energy makes it so that a second dislocation has to undo the APB energy created by the first. In doing so, this significantly reduces the mobility of dislocations in the material which should inhibit dislocation activated creep. These dislocation pairs (also called superdislocations ) have been described as being either weakly or strongly coupled, the spacing between the dislocations compared to the size of the particle diameter being the determining factor between weak and strong. A weakly coupled dislocation has a relatively large spacing between the dislocations compared to the particle diameter while a strongly coupled dislocation has a relatively comparable spacing compared to the particle diameter. This is determined not by the dislocation spacing, but by the size of the 𝛾’ particles. A weakly coupled dislocation occurs when the particle size is relatively small while a strongly coupled dislocation occurs when the particle size is relatively large (such as when a superalloy has been aged for too long). Weakly coupled dislocations exhibit pinning and bowing of the dislocation line on the 𝛾’-particles. Strongly coupled dislocation behavior depends greatly on the dislocation line lengths and the resistances benefits they offer disappear once the particle size becomes large enough.

Additionally, superalloys exhibit comparatively superior high temperature creep resistance due to thermally activated cross-slip of dislocations. When one of the dislocations in the pair cross-slips into another plane, the dislocations become pinned since they can no longer move as a pair. This pinning reduces the ability for the dislocations to move in dislocation activated creep and improving the creep resistant properties of the material.

Increasing the lattice misfit between 𝛾/𝛾' has also been shown to be beneficial for creep resistance. This is primarily since a high lattice misfit between the two phases results in a higher barrier to dislocation motion than a low lattice misfit.

For Ni-based single-crystal superalloys, upwards of ten different kinds of alloying additions can be seen to improve creep-resistance and overall mechanical properties. Alloying elements include Cr, Co, Al, Mo, W, Ti, Ta, Re, and Ru. Elements such as Co, Re, and Ru have been described to improve creep resistance by facilitating the formation of stacking faults by reducing the stacking fault energy. Increasing number of stacking faults leading to the inhibition of dislocation motion. Other elements (Al, Ti, Ta) can favorably partition into and improve the nucleation of 𝛾’-phase.

Diffusion is also a method of creep, and there are a few ways to limit diffusional creep. One primary way that superalloys can limit diffusional creep is by manipulating grain structure to reduce grain boundaries which tend to be pathways for easy diffusion. Typically this is done by manufacturing the superalloys as single crystals oriented parallel to the direction of the applied force.

Processing
Superalloys were originally iron-based and cold wrought prior to the 1940s when investment casting of cobalt base alloys significantly raised operating temperatures. The 1950s development of vacuum melting allowed for fine control of the chemical composition of superalloys and reduction in contamination and in turn led to a revolution in processing techniques such as directional solidification of alloys and single crystal superalloys.

Processing methods vary widely depending on the required properties of each item.

Casting and forging
Casting and forging are traditional metallurgical processing techniques that can be used to generate both polycrystalline and monocrystalline products. Polycrystalline casts offer higher fracture resistance, while monocrystalline casts offer higher creep resistance.

Jet turbine engines employ both crystalline component types to take advantage of their individual strengths. The disks of the high-pressure turbine, which are near the central hub of the engine are polycrystalline. The turbine blades, which extend radially into the engine housing, experience a much greater centripetal force, necessitating creep resistance, typically adopting monocrystalline or polycrystalline with a preferred crystal orientation.

Investment casting
Investment casting is a metallurgical processing technique in which a wax form is fabricated and used as a template for a ceramic mold. A ceramic mold is poured around the wax form and solidifies, the wax form is melted out of the ceramic mold, and molten metal is poured into the void left by the wax. This leads to a metal form in the same shape as the original wax form. Investment casting leads to a polycrystalline final product, as nucleation and growth of crystal grains occurs at numerous locations throughout the solid matrix. Generally, the polycrystalline product has no preferred grain orientation.

Directional solidification
Directional solidification uses a thermal gradient to promote nucleation of metal grains on a low temperature surface, as well as to promote their growth along the temperature gradient. This leads to grains elongated along the temperature gradient, and significantly greater creep resistance parallel to the long grain direction. In polycrystalline turbine blades, directional solidification is used to orient the grains parallel to the centripetal force. It is also known as dendritic solidification.

Single crystal growth
Single crystal growth starts with a seed crystal that is used to template growth of a larger crystal. The overall process is lengthy, and machining is necessary after the single crystal is grown.

Powder metallurgy
Powder metallurgy is a class of modern processing techniques in which metals are first powdered, and then formed into the desired shape by heating below the melting point. This is in contrast to casting, which occurs with molten metal. Superalloy manufacturing often employs powder metallurgy because of its material efficiency - typically much less waste metal must be machined away from the final product—and its ability to facilitate mechanical alloying. Mechanical alloying is a process by which reinforcing particles are incorporated into the superalloy matrix material by repeated fracture and welding.

Sintering and hot isostatic pressing
Sintering and hot isostatic pressing are processing techniques used to densify materials from a loosely packed "green body" into a solid object with physically merged grains. Sintering occurs below the melting point, and causes adjacent particles to merge at their boundaries, creating a strong bond between them. In hot isostatic pressing, a sintered material is placed in a pressure vessel and compressed from all directions (isostatically) in an inert atmosphere to affect densification.

Additive manufacturing
Selective laser melting (also known as powder bed fusion) is an additive manufacturing procedure used to create intricately detailed forms from a CAD file. A shape is designed and then converted into slices. These slices are sent to a laser writer to print the final product. In brief, a bed of metal powder is prepared, and a slice is formed in the powder bed by a high energy laser sintering the particles together. The powder bed moves downwards, and a new batch of metal powder is rolled over the top. This layer is then sintered with the laser, and the process is repeated until all slices have been processed. Additive manufacturing can leave pores behind. Many products undergo a heat treatment or hot isostatic pressing procedure to densify the product and reduce porosity.

Coatings
In modern gas turbines, the turbine entry temperature (~1750K) exceeds superalloy incipient melting temperature (~1600K), with the help of surface engineering.

Types
The three types of coatings are: diffusion coatings, overlay coatings, and thermal barrier coatings. Diffusion coatings, mainly constituted with aluminide or platinum-aluminide, is the most common. MCrAlX-based overlay coatings (M=Ni or Co, X=Y, Hf, Si) enhance resistance to corrosion and oxidation. Compared to diffusion coatings, overlay coatings are more expensive, but less dependent on substrate composition, since they must be carried out by air or vacuum plasma spraying (APS/VPS) or electron beam physical vapour deposition (EB-PVD). Thermal barrier coatings provide by far the best enhancement in working temperature and coating life. It is estimated that modern TBC of thickness 300 μm, if used in conjunction with a hollow component and cooling air, has the potential to lower metal surface temperatures by a few hundred degrees.

Thermal barrier coatings
Thermal barrier coatings (TBCs) are used extensively in gas turbine engines to increase component life and engine performance. A coating of about 1-200 μm can reduce the temperature at the superalloy surface by up to 200 K. TBCs are a system of coatings consisting of a bond coat, a thermally grown oxide (TGO), and a thermally insulating ceramic top coat. In most applications, the bond coat is either a MCrAlY (where M=Ni or NiCo) or a Pt modified aluminide coating. A dense bond coat is required to provide protection of the superalloy substrate from oxidation and hot corrosion attack and to form an adherent, slow-growing surface TGO. The TGO is formed by oxidation of the aluminum that is contained in the bond coat. The current (first generation) thermal insulation layer is composed of 7wt % yttria-stabilized zirconia (7YSZ) with a typical thickness of 100–300 μm. Yttria-stabilized zirconia is used due to its low thermal conductivity (2.6W/mK for fully dense material), relatively high coefficient of thermal expansion, and high temperature stability. The electron beam-directed vapor deposition (EB-DVD) process used to apply the TBC to turbine airfoils produces a columnar microstructure with multiple porosity levels. Inter-column porosity is critical to providing strain tolerance (via a low in-plane modulus), as it would otherwise spall on thermal cycling due to thermal expansion mismatch with the superalloy substrate. This porosity reduces the thermal coating's conductivity.

Bond coat
The bond coat adheres the thermal barrier to the substrate. Additionally, the bond coat provides oxidation protection and functions as a diffusion barrier against the motion of substrate atoms towards the environment. The five major types of bond coats are: the aluminides, the platinum-aluminides, MCrAlY, cobalt-cermets, and nickel-chromium. For aluminide bond coatings, the coating's final composition and structure depends on the substrate composition. Aluminides lack ductility below 750 °C, and exhibit limited thermomechanical fatigue strength. Pt-aluminides are similar to the aluminide bond coats except for a layer of Pt (5—10 μm) deposited on the blade. The Pt aids in oxide adhesion and contributes to hot corrosion, increasing blade lifespan. MCrAlY does not strongly interact with the substrate. Normally applied by plasma spraying, MCrAlY coatings from secondary aluminum oxides. This means that the coatings form an outer chromia layer and a secondary alumina layer underneath. These oxide formations occur at high temperatures in the range of those that superalloys usually encounter. The chromia provides oxidation and hot-corrosion resistance. The alumina controls oxidation mechanisms by limiting oxide growth by self-passivating. The yttrium enhances oxide adherence to the substrate, and limits the growth of grain boundaries (which can lead to coat flaking). Addition of rhenium and tantalum increases oxidation resistance. Cobalt-cermet-based coatings consisting of materials such as tungsten carbide/cobalt can be used due to excellent resistance to abrasion, corrosion, erosion, and heat. These cermet coatings perform well in situations where temperature and oxidation damage are significant concerns, such as boilers. One of cobalt cermet's unique advantages is minimal loss of coating mass over time, due to the strength of carbides. Overall, cermet coatings are useful in situations where mechanical demands are equal to chemical demands. Nickel-chromium coatings are used most frequently in boilers fed by fossil fuels, electric furnaces, and waste incineration furnaces, where the danger of oxidizing agents and corrosive compounds in the vapor must be addressed. The specific method of spray-coating depends on the coating composition. Nickel-chromium coatings that also contain iron or aluminum provide better corrosion resistance when they are sprayed and laser glazed, while pure nickel-chromium coatings perform better when thermally sprayed exclusively.

Process methods
Several kinds of coating process are available: pack cementation process, gas phase coating (both are a type of chemical vapor deposition (CVD)), thermal spraying, and physical vapor deposition. In most cases, after the coating process, near-surface regions of parts are enriched with aluminium in a matrix of the nickel aluminide.

Pack cementation
Pack cementation is a widely used CVD technique that consists of immersing the components to be coated in a metal powder mixture and ammonium halide activators and sealing them in a retort. The entire apparatus is placed inside a furnace and heated in a protective atmosphere to a lower than normal temperature that allows diffusion, due to the halide salts chemical reaction that causes a eutectic bond between the two metals. The surface alloy that is formed due to thermal-diffused ion migration has a metallurgical bond to the substrate and an intermetallic layer found in the gamma layer of the surface alloys.

The traditional pack consists of four components at temperatures below (750 °C):

 * Substrate or parts

 * Ferrous and non-ferrous powdered alloy: (Ti and/or Al, Si and/or Zn, B and/ or Cr)

 * Halide salt activator: Ammonium halide salts

 * Relatively inert filler powder (Al2O3, SiO2, or SiC)

This process includes:

 * Aluminizing
 * Chromizing
 * Siliconizing
 * Sherardizing
 * Boronizing
 * Titaniumizing

Pack cementation has reemerged when combined with other chemical processes to lower the temperatures of metal combinations and give intermetallic properties to different alloy combinations for surface treatments.

Thermal spraying
Thermal spraying involves heating a feedstock of precursor material and spraying it on a surface. Specific techniques depend on desired particle size, coat thickness, spray speed, desired area, etc. Thermal spraying relies on adhesion to the surface. As a result, the surface of the superalloy must be cleaned and prepared, and usually polished, before application.

Plasma spraying
Plasma spraying offers versatility of usable coatings, and high-temperature performance. Plasma spraying can accommodate a wide range of materials, versus other techniques. As long as the difference between melting and decomposition temperatures is greater than 300 K, plasma spraying is viable.

Gas phase
Gas phase coating is carried out at higher temperatures, about 1080 °C. The coating material is usually loaded onto trays without physical contact with the parts to be coated. The coating mixture contains active coating material and activator, but usually not thermal ballast. As in the pack cementation process, gaseous aluminium chloride (or fluoride) is transferred to the surface of the part. However, in this case the diffusion is outwards. This kind of coating also requires diffusion heat treatment.

Failure mechanisms
Failure of thermal barrier coating usually manifests as delamination, which arises from the temperature gradient during thermal cycling between ambient temperature and working conditions coupled with the difference in thermal expansion coefficient of substrate and coating. It is rare for the coating to fail completely – some pieces remain intact, and significant scatter is observed in the time to failure if testing is repeated under identical conditions. Various degradation mechanisms affect thermal barrier coating, and some or all of these must operate before failure finally occurs: Additionally, TBC life is sensitive to the combination of materials (substrate, bond coat, ceramic) and processes (EB-PVD, plasma spraying) used.
 * Oxidation at the interface of thermal barrier coating and underlying bond coat;
 * Depletion of aluminum in bond coat due to oxidation and diffusion with substrate;
 * Thermal stresses from mismatch in thermal expansion coefficient and growth stress due to the formation of thermally grown oxide layer;
 * Imperfections near thermally grown oxide layer;
 * Various other complicating factors during engine operation.

Turbines
Nickel-based superalloys are used in load-bearing structures requiring the highest homologous temperature of any common alloy system (Tm = 0.9, or 90% of their melting point). Among the most demanding applications for a structural material are those in the hot sections of turbine engines (e.g. turbine blade). They comprise over 50% of the weight of advanced aircraft engines. The widespread use of superalloys in turbine engines coupled with the fact that the thermodynamic efficiency of turbine engines is a function of increasing turbine inlet temperatures has provided part of the motivation for increasing the maximum-use temperature of superalloys. From 1990-2020, turbine airfoil temperature capability increased on average by about 2.2 °C/year. Two major factors have made this increase possible: About 60% of the temperature increases related to advanced cooling, while 40% have resulted from material improvements. State-of-the-art turbine blade surface temperatures approach 1,150 C. The most severe stress and temperature combinations correspond to an average bulk metal temperature approaching 1,000 C..
 * Processing techniques that improved alloy cleanliness (thus improving reliability) and/or enabled the production of tailored microstructures such as directionally solidified or single-crystal material.
 * Alloy development resulting in higher temperature materials primarily through the additions of refractory elements such as Re, W, Ta, and Mo.

Although Ni-based superalloys retain significant strength to 980 C, they tend to be susceptible to environmental attack because of the presence of reactive alloying elements. Surface attack includes oxidation, hot corrosion, and thermal fatigue.

Energy production
High temperature materials are valuable for energy conversion and energy production applications. Maximum energy conversion efficiency is desired in such applications, in accord with the Carnot cycle. Because Carnot efficiency is limited by the temperature difference between the hot and cold reservoirs, higher operating temperatures increase energy conversion efficiency. Operating temperatures are limited by superalloys, limiting applications to around 1000 °C-1400 °C. Energy applications include: Alumina-forming stainless steel is weldable and has potential for use in automotive applications, such as for high temperature exhaust piping and in heat capture and reuse.
 * Solar thermal power plants (stainless steel rods containing heated water)
 * Steam turbines (turbine blades and boiler housing)
 * Heat exchangers for nuclear reactor systems

Radiolysis
Sandia National Laboratories is studying radiolysis for making superalloys. It uses nanoparticle synthesis to create alloys and superalloys. This process holds promise as a universal method of nanoparticle formation. By developing an understanding of the basic material science, it might be possible to expand research into other aspects of superalloys. Radiolysis produces polycrystalline alloys, which suffer from an unacceptable level of creep.

Austenitic steel
Stainless steel alloys remain a research target because of lower production costs, as well as the need for an austenitic stainless steel with high-temperature corrosion resistance in environments with water vapor. Research focuses on increasing high-temperature tensile strength, toughness, and creep resistance to compete with Ni-based superalloys.

Oak Ridge National Laboratory is researching austenitic alloys, achieving similar creep and corrosion resistance at 800 °C to that of other austenitic alloys, including Ni-based superalloys.

AFA superalloys
Development of AFA superalloys with a 35 wt.% Ni-base have shown potential for use in operating temperatures upwards to 1,100 °C.

Multi-principal-element superalloy (MPES)
Researchers at Sandia Labs, Ames National Laboratory and Iowa State University reported a 3D-printed superalloy composed of 42% aluminum, 25% titanium, 13% niobium, 8% zirconium, 8% molybdenum and 4% tantalum. Most alloys are made chiefly of one primary element, combined with low amounts of other elements. In contrast MPES have substantial amounts of three or more elements.

Such alloys promise improvements on high-temperature applications, strength-to-weight, fracture toughness, corrosion and radiation resistance, wear resistance, and others. They reported ratio of hardness and density of 1.8–2.6 GPa-cm3/g, which surpasses all known alloys, including intermetallic compounds, titanium aluminides, refractory MPEAs, and conventional Ni-based superalloys. This represents a 300% improvement over Inconel 718 based on measured peak hardness of 4.5 GPa and density of 8.2 g/cm3, (0.55 GPa-cm3/g).

The material is stable at 800 °C, hotter than the 570+ °C found in typical coal-based power plants.

The researchers acknowledged that the 3D printing process produces microscopic cracks when forming large parts, and that the feedstock includes metals that limit applicability in cost-sensitive applications.

title: Superalloy


text:
Wikipedia:Articles for deletion/Ear piece bandit

 This page is an archive of the discussion about the proposed deletion of the article below. This page is no longer live. Further comments should be made on the article's talk page rather than here so that this page is preserved as an historic record. The result of the debate was delete --cesarb 09:09, 22 Jun 2005 (UTC)

Ear piece bandit
Unfortunately, armed bank robberies are common enough not to be usually notable. Physchim62 16:49, 11 Jun 2005 (UTC)

 * Keep - http://www.fbi.gov/mostwant/unkn/earpiece.htm --It seems slightly more well known than an ordinary armed robbery and compared to some of the stuff we keep I think it meets notability requirements. gren 16:53, 11 Jun 2005 (UTC)
 * Comment. Off the bat, I'm inclined to think that as a rule of thumb, anyone who makes the FBI's Most Wanted list has gained enough notoriety to be notable enough. That said, I know that a lot of these people aren't that notable -- they're just criminals who haven't been caught. Still, at least this guy does have a catchy nickname and some notoriety... Anyway, this appears to be a copyright violation, as the text has been lifted from the FBI wanted poster linked above, so it'd have to be rewritten. -- Captain Disdain 20:59, 11 Jun 2005 (UTC)
 * PD as a product of the U.S. federal government? Uppland 23:03, 11 Jun 2005 (UTC)
 * That might be true... but you'd still need to cite it (even if copying is legitimate) and it wouldn't make for a very good article just reading like it did there would it? gren 02:14, 12 Jun 2005 (UTC)
 * Most Wanted Posters are in the public domain -- the FBI wants them copied and transmitted as far and wide as possible. Xoloz 04:32, 12 Jun 2005 (UTC)
 * Delete non notable. JamesBurns 05:24, 12 Jun 2005 (UTC)
 * Delete per Physchim62 and JamesBurns. Quale 19:54, 15 Jun 2005 (UTC)

 * This page is now preserved as an archive of the debate and, like some other VfD subpages, is no longer 'live'. Subsequent comments on the issue, the deletion, or the decision-making process should be placed on the relevant 'live' pages.  Please do not edit this page .

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
Talk:Christian Apologetics and Research Ministry

Calvinist
I keep adding ", a Calvinist", after the initial point where it says Matt Slick's name. As the source, I use his own site, The Calvinist Corner, located at http://www.mslick.com/. This site clearly lists Matt Slick as the author, and the mode of writing on the page is clearly speaking in support of Calvinism. I believe the source is adequate documentation that Matt Slick is a Calvinist. The fact that Matt Slick is Calvinist was added on 20:43, 16 January 2007 after consensus on the talk page (with me originally starting the campaign to add it). The article was drastically cut short or rewritten on 00:27, 19 September 2009, at which point the Calvinism note went away with most of the rest of the page. Seeing the article another year later, I noticed that it was missing and re-added it. Now nobody wants to add it, it seems. My addition keeps getting reverted. What can we do to get this resolved? I believe it's important to mention Matt Slick's religion here, as ultimately any evangelism or apologetics that CARM does will be in agreement with that religion because he is the author. --Mister Magotchi (talk) 19:46, 2 December 2010 (UTC)
 * Any significant weight given to this particular POV, in secondary WP:RS sources? -- Cirt (talk) 19:50, 2 December 2010 (UTC)
 * I will do some Googling to find out if there are any, but I don't believe it is necessary to find any other sources in this case. Matt Slick, the author, is claiming to be a Calvinist on this source.  Nobody else determines Matt Slick's religion apart from Matt Slick himself.  Also, that Matt Slick is a Calvinist is NPOV.  You keep referring to it as a POV, but it isn't.  It is a fact with no room for opinion either way.  Matt Slick himself claims to be a Calvinist, so he is a Calvinist. --Mister Magotchi (talk) 20:56, 2 December 2010 (UTC)
 * Although this isn't a source from book, major news site, etc., which I imagine you're looking for, here's a page on CARM.org where Matt Slick says "I am a Calvinist...". --Mister Magotchi (talk) 21:11, 2 December 2010 (UTC)
 * Do any secondary sources say that this is particularly noteworthy? Otherwise, advocating this, is simply your own POV. -- Cirt (talk) 21:16, 2 December 2010 (UTC)
 * I don't know what will satisfy your POV on what is a good source in this case, because Matt Slick isn't particularly newsworthy, but right now, there are about 14,500 results on Google for ' "matt slick" calvinist '.  Pick one. --Mister Magotchi (talk) 22:06, 2 December 2010 (UTC)
 * Please cite a specific secondary source which states why this is noteworthy of inclusion in this article. -- Cirt (talk) 22:22, 2 December 2010 (UTC)
 * You are being uneven in your application of how you interpret the rules. carm.org is used in five citations on this article.  Three of them don't have secondary sources talking about the notability of the facts.  All I can find for sources of the notability of his Calvinism are other sites writing things against him, but as I have a relatively low amount of experience on Wikipedia, I don't know exactly what threshold the sources have to meet in order to be considered reliable.  Either way, if you're going to not allow me to make a note of his Calvinism on the basis that I can't find a secondary source claiming it's notable, the rule should be applied to the other instances on the page where carm.org is cited as well.  —Preceding unsigned comment added by Mister Magotchi (talk • contribs) 22:41, 2 December 2010 (UTC)
 * Those other instances are simple factual material, not trying to push a particular POV, as you are doing here. Let us discuss one issue at a time please, thanks. -- Cirt (talk) 04:46, 3 December 2010 (UTC)
 * Explain to me how identifying the religion of a theologian and apologist is POV? I would think the desire to omit such information is more POV than its inclusion.  I don't care that it be as prominent as I had it (in the first paragraph), but it certainly deserves a mention somewhere in the article. --Mister Magotchi (talk) 08:28, 3 December 2010 (UTC)

My view on this is probably similar (but probably not identical) to Cirt's. Speaking for myself, I have two problems with the use of "Calvinist" on this basis: (i) there are multiple ways that calling a website 'The Calvinist Corner' -- the most obvious is that Slick is writing from a Calvinist perspective. Another might be that he is writing about Calvinism. To take the former as true, and draw the the conclusion that Slick is a Calvinist is an inference and thus WP:Synthesis. It's most probably true, but not the sort of thing we're meant to be doing on Wikipedia. (ii) There's a fairly strong Calvinist thread through much (most?) of conservative evangelical Christianity. There are probably dozens of articles where we could find a similar level of evidence for applying the word 'Calvinist'. We don't, and to my mind shouldn't, unless a WP:SECONDARY source feels it sufficiently relevant/important a description to make use of it. This means that such articles aren't 'loaded up' with true-but-of-doubtful-relevance WP:IINFO descriptions. I suspect that part of the problem is that much of the secondary-source writing concentrates on CARM rather than Slick personally. However this simply means that, per WP:DUE, we should follow suit. HrafnTalkStalk(P) 05:13, 3 December 2010 (UTC)
 * Agreed. -- Cirt (talk) 05:16, 3 December 2010 (UTC)
 * This article is sorely lacking in a particular area, and that is the definition of the faith perspective of CARM. Slick's personal religious views are secondary to CARM's in this article, but nevertheless important, being that this organization is mostly a one-man show. As a newcomer to reading this article, I found it impossible to discern what CARM believes (beyond being 'Christian',) based on what is presented in the article. That was my number one question about their identity, and I was quite satisfied with the answers given on the primary source, carm.org. I strongly suggest that some overview of CARM's beliefs be presented. WP:SECONDARY says, Any interpretation of primary source material requires a reliable secondary source for that interpretation. A primary source may only be used on Wikipedia to make straightforward, descriptive statements that any educated person, with access to the source but without specialist knowledge, will be able to verify are supported by the source. I don't see how reproducing tenets of CARM's (and by extension, Slick's) beliefs, violates any Wikipedia guideline on primary sources or NPOV. Elizium23 (talk) 05:29, 3 December 2010 (UTC)
 * On Wikipedia what is or is not noteworthy is assessed by virtue of its already having been discussed in secondary sources. Your personal opinions about the current article's state may or may not be valid, but are irrelevant without backing of secondary sources. -- Cirt (talk) 05:54, 3 December 2010 (UTC)
 * Two problems with this view is (i) most readers who are not religious scholars would only have a vague understanding what 'Calvinism' (stated baldly) really means & (ii) Calvinism actually covers a fairly broad range of theological viewpoints (as you would expect to have evolved over several centuries, based on the work of a major theological innovator). For this reason, I think we need to find secondary sources that infer, analyse, and give context to Slick's views, rather than simply baldly state them based upon WP:SYNTH of his website's title. The latter is both bad policy-wise, and fails to inform the reader. HrafnTalkStalk(P) 07:11, 3 December 2010 (UTC)
 * Please read my 3rd comment of the initial discussion above where I link to the page with Matt Slick saying "I am a Calvinist...". It certainly is not under the umbrella of WP:SYNTH.  Cirt isn't complaining that my source is incorrect in calling him Calvinist.  He's saying that the fact that he's Calvinist isn't notable enough for the article.  I disagree, but since I'm not a seasoned Wikipedia veteran, and since he carries the banhammer, I can't really refute him. --Mister Magotchi (talk) 08:22, 3 December 2010 (UTC)
 * Yes, well, I tend to pay closer attention to sources cited in the article (which were WP:SYNTH), than ones mentioned in talk, so I overlooked that one. Sorry. But I think my other points stand. HrafnTalkStalk(P) 09:24, 3 December 2010 (UTC)

Matt Slick says he is a Calvinist. - http://carm.org/what-i-believe-matt-slick In fact, Matt Slick describes himself as a "five point calvinist," which is in reference to TULIP, an acronym made up at the Synod of Dordt 54 years after John Calvin's death. To reflect the comment made above about there being diverse ideas of calvinism one can review this statement by John Calvin regarding Acts 2:21 - "Therefore, forasmuch as no man is excluded from calling upon God, the gate of salvation is set open unto all men; neither is there any other thing which keepeth us back from entering in, save only our own unbelief." http://www.sacred-texts.com/chr/calvin/cc36/cc36018.htm This statement does not agree with the idea of "Limited Atonement" or "Irresistible Grace." Therefore, one who believes in TULIP should probably be defined as a Hyper-Calvinist, like Matt Slick.Easeltine (talk) 00:42, 23 June 2014 (UTC)
 * CARM is a multistaff organization. CARM does not state it is a Calvinist organization in its statement of faith. Calvinists well-known TULIP criteria for Calvinism is not met in its statement of faith (TULIP stands for: total depravity; Unconditional Election; Limited Atonement; Unconditional Election, Perseverance of the Saints).  For example, many Baptist believe in eternal security (perseverance of the saints), but are not Calvinists. Limited atonement is a key criteria for Calvinism and the statement of faith does not affirm limited atonement.

 * There are not third-party reliable sources indicating that CARM is a Calvinist organization.Knox490 (talk) 17:14, 1 July 2020 (UTC)
 * CARM's statement of faith indicates: "CARM does not take a stand for or against Calvinism or Arminianism. CARM recognizes that there are many godly Christians in both theological camps.  Some of CARM's writers are Calvinists and some are Arminians."

 * This should settle the matter.Knox490 (talk) 18:55, 1 July 2020 (UTC)

Criticism section needed
The CARM website is hostile to a number of religions, namely Roman Catholicism, Seventh-Day Adventism, and Mormonism, to name a few. This article needs to address this fact in a balanced, encyclopedic manner. —Preceding unsigned comment added by 69.245.213.46 (talk) 19:59, 12 February 2011 (UTC)

 * Go right ahead! Elizium23 (talk) 20:05, 12 February 2011 (UTC)
 * Not to mention their misrepresentation of Science! Their belief they can "explain away" Evolution in a few short articles! Not being able to make solid argument for literal biblicalism! --Nutthida (talk) 11:08, 7 January 2012 (UTC)

In the home article of its bits on Roman Catholicism it asks "Dear Catholic, do you know for sure if you are going to heaven?" which is a downright stupid and contradictory question; Catholic belief is that absolutely nobody is saved until they die. I really wish people would get to know stuff properly before criticising it. 86.42.121.148 (talk) 03:47, 16 June 2014 (UTC)

NPOV
I thought the commentary section was riddled with NPOV problems. Very selective quotemining, almost all weasely/skeptical-sounding. The page needs to be worked on to contain more substantial information about the group, preferably with more neutral-sounding commentary. BabyJonas (talk) 04:26, 15 May 2012 (UTC)

Woah. How is this article still up in its current form. Needs serious work! 24.21.151.167 (talk) 08:56, 26 October 2014 (UTC)
 * I removed the Douglas E. Cowan citation which indicated that one of Slick's books was self-published (Right Answers for Wrong Beliefs. Sovereign World, Ltd. ISBN 1-85240-279-2). Worldcat says a publishing company published the book which I indicated in my edit summary.

 * Above the reception section of CARM's Wikipedia article there was a note questioning the relevancy of the section that Wikipedia editor User: Approaching indicated (relevancy of the countercult criticism). I agree with User: Approaching so I improved the relevancy of the reception section. For example, the whole countercult section in the reception section by Cowan is a big digression so I removed it. CARM is a Christian apologetics ministry that also has full time missionaries. It is not a counter cults organization and has never been one. I question the accuracy of Cowan's criticism as he appears to have been wrong about the self-publishing matter.Knox490 (talk) 18:07, 1 July 2020 (UTC)

Notability & Verifiability
I am moving to the view this article may run afoul of what wikipedia is not. Should this article be proposed for deletion? Basileias (talk) 14:48, 15 February 2015 (UTC)

Is it not apparent to anyone else that this CARM is a joke, a set-up by Matt Slick? I tackled the questionnaire on what atheists think. After spending an hour on it, trying to explain my views, the last couple of questions made it clear that the whole thing was a set up, a joke. Am I hallucinating, or is this a fact? Dfs9491 (talk) 05:43, 24 August 2016 (UTC)dfs9491

NPOV issues in Reception section
The Reception section of the article is almost entirely praise for CARM, much of it from an evangelical Christian perspective. For the sake of fairness, more sources which are critical or neutral towards CARM should probably be added. As it stands, the article comes across as promoting the organization. 77.102.218.164 (talk) 14:44, 6 January 2024 (UTC)


text:
Category:Mountains of Libya

The mountains of Libya.

title: Category:Mountains of Libya


text:
Wikipedia:Articles for deletion/King of Pop

 This page is an archive of the discussion about the proposed deletion of the article below. This page is no longer live. Further comments should be made on the article's talk page rather than here so that this page is preserved as an historic record. The result of the debate was merge and redirect. Rossami (talk) 21:28, 22 Jun 2005 (UTC)

King of Pop
Inherently POV.
 * Clean up
 * Delete     16:52, 11 Jun 2005 (UTC)
 * Merge with Wacko Jacko into Michael Jackson slogans. 81.156.176.226 11:19, 12 Jun 2005 (UTC)

 * Keep or redirect... this title is definitely well known as being used with Jackson. I don't think it's any more POV than "Prophet Muhammad" or "Prophet Bahá'u'lláh" -all are titles given to them that not everyone accepts...? I think that makes sense gren 17:04, 11 Jun 2005 (UTC)
 * But we don't allow "Jesus Christ", only "Jesus". And Muhammad is listed under "Muhammad" rather than "Prophet Muhammad", so I don't see how that is an argument.     11:10, 12 Jun 2005 (UTC)
 * I suppose then you'd agree with the redirect part of my statement. gren 17:12, 15 Jun 2005 (UTC)

 * Keep, of course. Well known title, used by many people, and this is a good NPOV stub. sjorford →•← 17:15, 11 Jun 2005 (UTC)
 * Keep, notable title. You 19:59, Jun 11, 2005 (UTC)
 * Keep. Might need a little cleanup, but is in use.  humblefool® 21:38, 11 Jun 2005 (UTC)
 * Merge with Michael Jackson and redirect. This is almost a dicdef. 23skidoo 21:40, 11 Jun 2005 (UTC)
 * Redirect to Michael Jackson. Nestea 21:41, 11 Jun 2005 (UTC)
 * Keep. — Phil Welch 00:53, 12 Jun 2005 (UTC)
 * Merge and redirect. The article itself doesn't deserve a page (hell, why not create Jacko, Wacko Jacko, Court TV's favorite topic, etc.).  However, it is a well-known title, and it should be sent to the main M. Jackson page.
 * Delete POV not encyclopedic. JamesBurns 05:24, 12 Jun 2005 (UTC)
 * Merge with Michael Jackson --Xcali 05:42, 12 Jun 2005 (UTC)
 * Merge, along with Wacko Jacko, with Michael Jackson. --Idont Havaname 18:31, 12 Jun 2005 (UTC)
 * Delete Hiding 19:45, 12 Jun 2005 (UTC)
 * Comment if this is kept how many of these will there be? The king, The king of rock and roll, The godfather of soul? Hiding 19:45, 12 Jun 2005 (UTC)
 * It is a commonly given name to Michael Jackson... just like The King links to Elvis. I don't believe any of those others you mentioned are prominent. gren 20:02, 12 Jun 2005 (UTC)
 * Fair enough. I'll change my vote to Redirect to Michael Jackson.  I'd argue it's as prominent as James Brown being the Godfather of Soul though.

 * Redirect to Michael Jackson. Why does this require its own article? carmeld1 00:11, 13 Jun 2005 (UTC)
 * Merge/redirect, unless another King of Pop is suggested (as Jacko is a disambiguation...) Samaritan 21:39, 13 Jun 2005 (UTC)
 * Merge/redirect. It's a highly common epithet for Michael Jackson (one that is used for no one else), but no need to give it an independent article.  Postdlf 00:37, 14 Jun 2005 (UTC)
 * Merge/redirect ditto above Saswann 17:04, 15 Jun 2005 (UTC)
 * Keep, but needs cleaning-up to be whiter-than-white. The last sentence is a good candidate for BJAODN. Physchim62 20:45, 15 Jun 2005 (UTC)
 * Merge with Michael Jackson (literally copy, summarize a bit, wikify, and paste) and then redirect). --FuriousFreddy 01:17, 20 Jun 2005 (UTC)

 * This page is now preserved as an archive of the debate and, like some other VfD subpages, is no longer 'live'. Subsequent comments on the issue, the deletion, or the decision-making process should be placed on the relevant 'live' pages.  Please do not edit this page .


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Pinus occidentalis

Pinus occidentalis, also known as the Hispaniolan pine, Hispaniola pine or, is a pine tree endemic to the island of Hispaniola (split between the Dominican Republic and Haiti).

Ecology
It is the eponymous species of the Hispaniolan pine forests ecosystem, in which it constitutes a majority of the biomass present. Another endemic species, the Hispaniolan crossbill (Loxia megaplaga), feeds almost exclusively on the cones of P. occidentalis.

title: Pinus occidentalis


text: Category:Geography of Somalia

title: Category:Geography of Somalia


text:
Overseas Telecommunications Commission

The Overseas Telecommunications Commission (OTC) was established by Australia in August 1946. It inherited facilities and resources from Amalgamated Wireless Australasia (AWA) and Cable & Wireless, and was charged with responsibility for all international telecommunications services into, through and out of Australia. In effect, all overseas telecommunications was nationalized. Australia was adopting a Commonwealth-wide policy that had been adopted at the Commonwealth conference in 1945. The main goal was to end the artificial routing of traffic to cable or wireless depending on private financial profits.

On 1 February 1992 it was merged with Australia's domestic telecommunications carrier, the Australian Telecommunications Corporation ("Telecom Australia") to create the Australian and Overseas Telecommunications Corporation (AOTC). The new organisation underwent a corporate identity review and was subsequently renamed Telstra.

When first established in 1946, OTC inherited facilities which had been depleted during World War II, and faced rising costs and falling profits. From this tenuous beginning, the organisation was to grow over the years to gain world standing on the international telecommunications stage.

Throughout rapid developments in undersea cable networks, global satellite systems and burgeoning digital technologies, OTC maintained a keen watch over its services to ensure continued quality. It also maintained and developed its links with maritime services, one of the initial arms of Australia's international telecommunications network.

Background
When first established by an Act of Parliament in 1946, Australia's international telecommunications carrier – OTC – inherited facilities which had been depleted during World War II, and faced rising costs and falling profits. From this tenuous beginning, the organisation was to grow over the years to gain world standing on the international telecommunications stage.

The commission's role was the establishment, maintenance and operation of telecommunications services between Australia and other countries. Through the OTC communications, telegram, telephone, telex and photo-telegrams were relayed to other countries around the globe. To undertake these functions the commission was part owner of overseas cables and international satellite facilities and it also operated international and coastal radio services in Australia and its territories. The OTC could well call itself and its services ‘the World Shrinkers’

OTC's history shows how, by internal restructuring, upgrading its public image, making long-term investments in technologies and networks, and becoming a major player in international cooperative efforts, it played a vital role in the provision of Australia's international communications.

Throughout rapid developments in undersea cable networks, global satellite systems and burgeoning digital technologies, OTC maintained a keen watch over its services to ensure continued quality. It also maintained and developed its links with maritime services, one of the initial arms of Australia's international telecommunications network.

1940s
1946
 * 7 August: OTC established by the Overseas Telecommunications Act, 1946.
 * 23 August: First Commission appointed – James Malone appointed Chief Commissioner.
 * 1 October: OTC and AWA signed a Caretaker and Management Agreement under which AWA continued to control and operate radio services until such time as the commission had the resources to assume full control.
 * 19 October: JES Stevens appointed first General Manager of OTC.

1947
 * 1 February: OTC assumed full control of radio services from AWA.
 * 28 May: Trials of 5-unit teletype equipment conducted on the Sydney-San Francisco RCA Multiplex.
 * June: Tests conducted with the RMS Orlon as part of a series of experiments on the development of circuits to handle radiotelephone traffic with small ships in local waters, and overseas vessels leaving/entering Australian ports.
 * 1 July: Interim Management Agreement signed by OTC and Cable & Wireless. OTC assumed managerial control of the Australian international cable network but the assets remained with Cable and Wireless Ltd.
 * 7 July: Bassendean receiving station, Western Australia, closed.
 * 1 September: New shore-end laid for Pacific Cable at Fanning Island.
 * November: Beam Messenger Service discontinued.
 * 20 November: Direct Melbourne-Wellington, New Zealand, picture-gram service opened.

1948
 * 25 January: First Wagga Weekend (OTC annual staff sports carnival).
 * April: OTC's first Annual Report tabled in Parliament.
 * 11 May: First International Telecommunication Union meeting since World War II began in Brussels.
 * 12 July: Work commenced on a new station building for Darwin Radio.

1949
 * 15 January: Adelaide cable station closed.
 * 11 April: Arrangements completed for establishing a radiotelephone service between Australia and Royal Australian Navy ships at sea.
 * 1 May: Assets of Cable & Wireless purchased by the commission.
 * 2 May: Aerogram service commenced between Australian coast radio stations and Qantas and BOAC flights on the Sydney-UK route.
 * 19 May: International Telegraph and Telephone Conference (CCITT) began in Paris to revise international telegraph agreements.
 * 31 May: Commonwealth Telecommunications Board formed.
 * 14 December: OTC's first staff Christmas party held on Sydney Harbour.

1950s
1950
 * 1 February: Flat rates introduced for traffic to major foreign zones from Australia. Commercial rates to most foreign destinations also amended. All rates increased by 3d per word.
 * 1 April: Ownership and control of Cable & Wireless's assets in Australia passed to OTC. All staff except those hired locally at Fanning Island and Suva became members of OTC.
 * 5 May: Gangers arrived at Willis Island to remodel the radio station.
 * 8 June: New transmitting station opened at Port Moresby.
 * 15 June: Old Darwin Radio station closed. New station at Parap opened.
 * 5 July: Worldwide unification of telegram categories became effective.
 * 30 August: PMG's Department extended picture-gram service to all Australian capital cities, transmitted via OTC's Melbourne office.
 * 3 November: JL Mulholland appointed General Manager of OTC. New OTC logo sourced from Radio Hobbies Magazine.

1951
 * March: Installation of new phototelegram equipment completed at the Melbourne office.
 * 30 June: OTC's rates book revised to include zoning of rates to certain countries, unification of rates and abolition of government rates to certain countries.
 * 1 September: First Annual General Meeting held of the Sydney Office Staff Sports and Social Club.
 * 1 October: Ships' Letter Telegram service opened to all classes of vessels.

1952
 * 26 March: Sydney-San Francisco circuits converted to 5-unit code.
 * 15 April: Sydney-London telegraph traffic transferred to Electra House, Sydney. All London-Sydney traffic handled without tape relay at Melbourne.
 * 9 June: Transfer of coastal radio operations from Applecross to Bassendean. Applecross became remote controlled.
 * 20 October: Electra House became the single operating centre in Sydney.

1953
 * 1 June: Cost of all telegraph rates from Australia (excluding urgent press and press messages to USA) reduced by one-third.
 * 2 June: Radiotelegraph and cable channels rearranged to cater for heavy traffic during the Coronation of Elizabeth II. Two additional phototelegram channels opened. Bassendean Radio equipped with phototelegram equipment.
 * 8 August: OTC's central workshop facilities moved from Pennant Hills to Marrickville.
 * November: Sydney's central telegraph operations moved to Spring Street.
 * 6 December: Melbourne facsimile section received the first-ever picture for publication from a ship at sea (the Royal yacht Gothic en route to Fiji).
 * 15 December: First transmitter at Doonside brought into service.

1954
 * January: OTC's acceptance office in Perth closed.
 * 2 April: Doonside transmitting station closed and all services diverted to Fiskville and Pennant Hills.
 * 23 August: SF Kellock appointed new Chief Commissioner of OTC.

1955
 * 16 January: Cooktown Radio station closed.
 * 28 February: Adelaide acceptance office closed.
 * 9 July: Bringelly commenced monitoring Island Services. Transfer began of radiotelegraph channels from La Perouse to Bringelly.
 * 10 October: Bringelly HF radio station officially opened.

1956
 * 19 April: Trevor Housley appointed General Manager of OTC.
 * 27 April: Severe solar flare activity interrupted OTC's radiotelegraph services.
 * 17 August: Qantas leased a two-way radio teletype circuit to Singapore.
 * 25 September: First trans-Atlantic co-axial telephone cable, TAT-1 came into service.
 * December: During the Melbourne Olympic Games, a record amount of traffic was sent over Australia's international telecommunications channels. 9,408,254 words were sent over 22 leased channels which operated for some 5465 hours. 6730 radiotelephone calls were handled and 2296 phototelegrams were sent. 285 hours of radio broadcasts were sent over R/T channels.

1957
 * OTC adopted a new logo.
 * 28 February: Doonside transmitting station officially re-opened.
 * 5 October: Bringelly, Rockbank and Bassendean stations began monitoring transmissions from the world's first man-made satellite, Sputnik 1, launched by USSR.
 * 28 October: Lodgement of international telegrams via the international telex network came into operation - known as the 'printergram service'.

1958
 * OTC updated its logo.
 * 31 January: USA successfully launched its first satellite - Explorer 1.
 * 17 March: Direct radiotelephone service opened between Australia and Japan.
 * November: Official opening ceremonies heralded the new international telex services to Japan, USA, UK and Canada.
 * December: The USA launched its first delayed repeater satellite: 'Score'.

1959
 * 20 April: Commemorative cairn celebrating the landing of the Java-Darwin submarine telegraph cable unveiled in Darwin.
 * 28 September: The Pacific Cable Conference hosted by OTC in Sydney was officially opened by Prime Minister Robert Menzies. At this meeting, plans were drawn up for the construction of a new transpacific submarine telephone cable to be known as the Commonwealth Pacific Cable System (COMPAC).

1960s
1960
 * 4 February: OTC's new Melbourne office at Lonsdale Street officially opened.
 * 21 April: First meeting of the Pacific Cable Management Committee began in London.
 * 22 August: Ceremony held in Paddington to mark the commencement of work on OTC's new international terminal.
 * 23 August: MRC Stradwick appointed Chief Commissioner of OTC.
 * 31 August: Direct Australia-New Zealand telex service opened.
 * 14 November: Historic No 1 transmitter at Fiskville closed down.
 * 15 November: Radioteletype and voice frequency circuit opened between Sydney and Honolulu as part of preparations for a communications system being developed for NASA's Project Mercury (America's first crewed orbital flight).

1961
 * 3 January: A radioteletype and voice frequency circuit opened between Perth Radio and a ship in the Indian Ocean as part of preparations for NASA's Project Mercury.
 * 27 July: Delegates from Australia, Canada, New Zealand, Singapore and Malaya, Hong Kong, Sarawak, India, Pakistan, Brunei and North Borneo met in Kuala Lumpur to discuss the construction of a proposed new telephone link between Australia and SE Asia: the Seacom cable.
 * 23 September: Giles Chippindall appointed Chief Commissioner of OTC.
 * November: 5-unit code equipment installed at the Cottesloe cable station.
 * 12 December: The new trans-Atlantic telephone cable, Cantat, opened.

1962
 * March: Commonwealth Telecommunications Conference began in London to discuss satellite communications.
 * 19 April: Shore end of the COMPAC cable landed at Bondi Beach.
 * 2 June: The final splice was made on the trans-Tasman section of the COMPAC cable. OTC technician, Orme Cooper, made the first direct voice contact over the cable from Sydney to New Zealand.
 * July: Southport cable station closed.
 * 9 July: Prime Minister Robert Menzies officially opened the trans-Tasman section of the COMPAC cable.
 * 3 December: The Suva-Auckland link of the COMPAC cable officially opened.
 * 10 December: Norfolk Island cable station closed at Anson Bay.
 * 31 December: The new telephone exchange at Paddington terminal opened.

1963
 * 29 March: Adelaide Radio station was transferred from Rosewater to a new station at McLaren Vale.
 * April: New transmitting and receiving stations opened at Lae Radio.
 * 23 August: AE Chadwick appointed Chief Commissioner of OTC.
 * 3 December: The COMPAC cable was officially opened by Queen Elizabeth II addressing simultaneous ceremonies in London, Ottawa, Sydney and Wellington.

1964
 * New logo adopted
 * 15 January: New Townsville Radio station was officially opened at Pallarenda.
 * 16 January: Fanning Island cable station closed at 4.10 pm.
 * February: Representatives from OTC attended meetings in Rome and Tokyo to discuss investment plans for a world satellite communications network with European countries, the Japanese and the Americans.
 * 20 August: International Telecommunications Satellite organisation (Intelsat) was formed in Washington DC. OTC was one of the founding signatories to agreements setting forth interim arrangements; ensuring Australia's participation in the development of a global satellite communications system.

1965
 * 31 March: Singapore-Hong Kong section of the Seacom cable officially opened in Hong Kong.
 * April: The first Intelsat satellite, Early Bird, launched into orbit above the Atlantic.
 * 28 June: Government officials in Europe and the US exchange greetings via Early Bird.
 * September: The automatic transit telex exchange opened at OTC's Paddington terminal, replacing the old manual system which had been in place since 1958.
 * October: Agreement reached between NASA and OTC for the provision of a Satellite Earth Station (SES) at Carnarvon, Western Australia which would be linked with NASA's tracking station at Browns Flat and its control centre in the US.
 * November: NASA announced that the Intelsat satellite communications system would be used for its manned space flights to the moon. The Australian government gave its consent for the construction of an SES at Carnarvon, Western Australia.
 * December: Land was acquired on which to build a new radio transmitting station at Gnangara in Western Australia, which would be used to provide additional capacity for the NASA space project.
 * 3 December: The new radio receiving centre opened at Rabaul.

1966
 * 17 January: Harold White took up his duties as General Manager of OTC.
 * 26 February: Last messages were exchanged over the Cottesloe-Cocos Island-Rodriguez cable.
 * 6 May: New Brisbane Radio station opened at Toorbul.
 * 3 July: The new Melbourne Radio station officially opened at Cape Schanck.
 * 31 July: Cocos Islands cable station closed.
 * 29 October: Carnarvon SES officially opened and successfully tracked the first Intelsat II satellite as it passed over Australia during its transit orbit.
 * 25 November: First satellite television link-up between Australia and England was made possible because the first Intelsat II satellite did not reach synchronous orbit over the Pacific Ocean.

1967
 * New logo adopted.
 * 4 February: Australia's first satellite communications service opened via Carnarvon SES.
 * 30 March: Queen Elizabeth II officially opened the Seacom cable. Simultaneous ceremonies were held at Cairns, Guam, Madang, Hong Kong, Singapore and London.
 * 14 April: OTC headquarters in Sydney moved from Spring Street to new premises at Martin Place.
 * 17 April: Harold White, General Manager of OTC, was appointed chairman of the newly formed Commonwealth Telecommunications Council at its inaugural meeting held in London 17–28 April.
 * May: New international radio station opened at Gnangara.
 * October: A new staff magazine, Contact, was launched.
 * November: Time assignment speech interpolation equipment came into operation on the COMPAC cable, increasing the number of circuits from 80 to 100.

1968
 * Logo updated.
 * 29 March: Moree SES officially opened, followed by an international television linkup between Australia and Japan.
 * 1 April: The first commercial use of Moree SES came on this day when news stations in Melbourne broadcast US President Lyndon Johnson's announcement that he would not stand for re-election.
 * July: The radio transmitting station at Applecross closed.
 * 29 September: Sydney Operating Room moved to Martin Place.
 * 1 October: Arthur Petfield appointed Chief Commissioner of OTC.

1969
 * February: OTC's automatic message relay system became operational at the Paddington terminal. Carnarvon SES began service on a part-time basis as a TTC&M station for Intelsat.
 * 14 March: The first commercial satellite link to Asia opened between Australia and Japan.
 * 31 March: The Commonwealth Telecommunications Board was superseded by the Commonwealth Telecommunications Organisation.
 * 31 May: The original beam wireless stations at Fiskville and Rockbank closed.
 * 20 July: Pictures of the first man on the moon were telecast to the world via OTC facilities in Australia.
 * 1 October: The second satellite earth station at Carnarvon became operational. Carnarvon SES 1 assumed full TT&C functions.
 * 9 November: Australia became the first nation in the world to use satellite systems for domestic communications when 24 voice circuits were opened between Carnarvon SES and Moree SES.
 * 14 December: The new Ericsson gateway telephone exchange was brought into service at Paddington terminal.
 * 15 December: Ceduna SES came into service.

1970s
1970
 * New logo adopted.
 * 20 February: The official opening of Ceduna SES was held at the Adelaide Hotel Adelaide.
 * March: OTC's year-end figures showed that the revenue from international telephone services exceeded those of international telegraph services for the first time in the commission's history.
 * 21 June: OTC's new office in Brisbane officially opened.
 * 5 October: Fully automated telex system introduced onto the Australia-US service.

1971
 * 25 January: The first Intelsat IV satellite placed over the Atlantic.
 * 20 November: 100th-anniversary celebrations of the landing of the Java-Darwin cable held in Darwin.

1972
 * February: Transit resumed as OTC's staff magazine.
 * 6 February: The Gemini XII space capsule touring display arrived in Australia to be used for celebrating OTC's 25th anniversary.
 * March: Carnarvon Radio station opened.
 * 15 July: A direct radiotelephone service opened between Norfolk Island, Australia and beyond.

1973
 * February: The Australian Government established the Vernon Commission of Inquiry into the operation of Australia's postal and telecommunications services.
 * 27 November: The new Hobart Radio station opened.
 * 1 December: The assets and responsibilities for the operation of telecommunications services in Papua New Guinea were transferred from OTC to PNG.

1974
 * 21 February: Broadway terminal officially opened by Prime Minister Gough Whitlam.
 * March: Preliminary trials of air to ground radiotelephone services for Qantas conducted (concluding 1.4.74). Full-scale experimental trials began for Qantas flights over the Indian and Pacific Oceans.
 * 12 November: Alan George Gibbs appointed Chief Commissioner of OTC.
 * 25 December: Cyclone Tracy hit Darwin. OTC radio facilities suffered comparatively minor damage.

1975
 * May: Australia's first daily international television service commenced. Legislation passed in Parliament advocating the formation of Telecom Australia and Australia Post, and leaving OTC as a separate statutory authority. Telecom was established in July 1975.
 * June: Radio-teletype direct printing service established for ship-to-shore messages via Sydney Radio.
 * September: Robert Somervaille appointed Chief Commissioner of OTC.
 * 25 September: Shore end of the Tasman cable landed at Bondi Beach.
 * October: The world's first TASI-B (Time Assignment Speech Interpolation) equipment came into operation at OTC's Paddington terminal, effectively doubling the capacity of the COMPAC cable and 38 of the Seacom cable circuits.

1976
 * New logo adopted.
 * 12 January: OTC launched its first colour television advertising campaign: Circles.
 * February: Members of the International Maritime Consultative Organisation reached agreement on the need for a worldwide maritime satellite system.
 * 20 February: Tasman cable officially opened by Prime Minister Malcolm Fraser, speaking from Canberra to Prime Minister of New Zealand, Robert Muldoon.
 * 9 March: New ISD (International Subscriber Dialling) service launched at a press conference at OTC's Broadway terminal, coming into commercial operation on 1 April.
 * 23 July: A-PNG cable officially opened.
 * 31 November: Sydney Radio handled its first ever ship-to-ship telex connection between a vessel sailing in the Atlantic Ocean and one sailing in the Indian Ocean.

1977
 * February: OTC became the first signatory to the Inmarsat agreement.
 * 6 March: OTC's highly successful advertising campaign - Memories - went to air, promoting ISD.

1978
 * 19 May: Capacity of Broadway exchange telephone circuits increased from 2,400 to 6,000 with the installation of new equipment.
 * 18 July: Representatives from American, Japanese and Australian telecommunications organisations met at an international telephone conference to herald implementation of the new CCITT No 6 telephone signalling process. This process had been 15 years in the making, through international research and cooperation.
 * September: Marisat satellite communications terminals installed on the Australian vessels Robert Miller and the Australian Endeavour.

1979
 * 1 March: OTC's maritime radiotelephone service, Seaphone, launched from Melbourne Radio station.
 * 13 March: A new operating centre at La Perouse CRS officially opened.
 * 18 April: OTC's Midas (Multimode International Data Acquisition Service) came into commercial operation, providing Australian organisations with fast access to overseas information banks through use of advanced computer-based technology.
 * 4 May: W Schmidt appointed General Manager of OTC.
 * September: OTC's OverseasFax service came into commercial operation.

1980s
1980
 * 30 April: 50th anniversary of the inauguration of the Australia-UK direct telephone service.
 * 14 May: Representatives from 10 countries, including Australia, met at OTC House to sign a document committing those nations, in principle, to start work on a new trans-Pacific cable: ANZCAN.
 * June: The world's first optical fibre underwater telecommunications cable laid in Loch Fyne in Scotland to undergo trials.
 * 24 July: OTC's fifth satellite earth station, Ceduna 2, officially opened.
 * August: OTC's successful television advertising campaign - Friends - launched. OTC was awarded a five-year contract by the European Space Agency for the installation, maintenance and operation of VHF launch support facilities at Carnarvon SES.
 * 18 September: The Australian government expanded OTC's charter to give it interim ownership and management of Australia's national communications satellite system.
 * November: OTC launched its Intertel service.

1981
 * Canberra office officially opened: Kamal Ayoub appointed manager.
 * 10 April: The first Space Shuttle, Columbia, launched.
 * 23 April: Paddington terminal extensions officially opened by OTC's Chief Commissioner, Bob Somervaille.
 * October: OTC hosted the 8th South Pacific Regional Telecommunications meeting to discuss requirements and progress of telecommunications services for South Pacific nations.
 * November: The Australian Government announced the formation of a national body, Aussat, which would own and manage the new national satellite system.
 * 20 December: The first maritime communications satellite - Marecs-A - launched from French Guiana. Carnarvon SES used as a TTC&M station.

1982
 * 1 February: Inmarsat assumed control of its international maritime satellite communications network.
 * 14 April: OTC opened a new training centre at Marrickville.
 * October: The Commonwealth Games, held in Brisbane, led to a massive increase in international telecommunications traffic.
 * 3 November: Moree 2 SES was officially opened.
 * December: The Sydney-Hobart became the first yacht race in the world to be monitored using satellite communications. An AWA radio vessel was equipped with an Inmarsat terminal.

1983
 * 11 January: Shore end of the ANZCAN cable landed at Bondi Beach.
 * 19 August: OTC launched its new Minerva data communications service.
 * October: OTC established its own Research and Development Board.
 * 8 December: The new Norfolk Island cable station officially opened.

1984
 * 3 April: OTC hosted an International Teleconferencing Symposium at OTC House. Participants took part in a satellite link-up with other Intelsat member-nations.
 * 14 May: Healesville Satellite Earth Station officially opened near Melbourne.
 * July: OTC launched its Herogram service for athletes attending the Los Angeles Olympic Games. OTC was the only foreign international telecommunications organisation to have a presence at the Games.
 * 8 November: The ANZCAN cable was officially opened by Queen Elizabeth II speaking simultaneously to parties gathered at the Sydney Opera House, Auckland, Suva and Vancouver.
 * 30 November: The Compac cable was officially decommissioned.

1985
 * January: A new $6M computer system providing data processing services and detailed customer accounting was installed in OTC's Head Office.
 * 8 January: The cable laying vessel, CS Pacific Guardian, built in England, sailed into Sydney Harbour on her maiden voyage.
 * 20 February: George Maltby was appointed the first managing director of OTC.
 * 31 May: Shore end of the AIS cable landed at Whitford Beach, near Perth.
 * 23 July: The Intelsat Vista Earth station, installed by OTC on the Cocos Islands, opened.
 * November: Telex World Letter service introduced, allowing telex users to send messages to correspondents who did not own a telex machine.

1986
 * 18 July: The Seacom cable was taken out of service. Guam cable station closed.
 * 28 October: The Perth International Telecommunications Centre, and the AIS cable, were officially opened in Gnangara, WA.
 * 16 December: Prime Minister Bob Hawke launched the Request for Tenders for the Tasman 2 cable at an official function in Canberra.

1987
 * January: The Coastal Radio Service was officially renamed the OTC Maritime Communications Service.
 * 1 February: OTC celebrated its 40th anniversary of operations.
 * April: OTC adopted a new logo, and new corporate style.
 * 30 April: Carnarvon SES's TTC&M satellite dish was officially decommissioned.
 * 2 June: Amendments to the Overseas Telecommunications Act were announced, paving the way for OTC to expand its sales of developed software and provide consultancy services on communications systems to foreign countries. OTC announced the formation of OTC International Limited as its wholly owned international marketing subsidiary.
 * 1 July: The new Melbourne International Gateway opened at Scoresby.
 * 27 July: The Vietnam Vista satellite earth station was officially opened.
 * 11 November: Gareth Evans officially opened the new OTC House at 231 Elizabeth Street, Sydney.
 * 27 November: Oxford Falls (Sydney) SES officially opened. (A few days earlier, OTC held a barbecue lunch for staff involved in the project.)
 * 17 December: A contract between OTC, Telecom New Zealand and the Tasman Cable Company was signed for the construction and laying of the Tasman 2 optical fibre cable.

1988
 * January: Alan Coates appointed Chief Commissioner of OTC.
 * Apri18: OTC's Skystream service was officially opened at Sydney SES.
 * 28 June: The international videoconferencing studio was launched at OTC House.
 * 28 July: OTC opened its Bicentennial exhibition Settlement to Satellites - at Paddington terminal.
 * August: Moree SES closed.
 * 8 August: The new AXE 900 digital telephone exchange opened at Broadway terminal.
 * September: OTC International's proposal for a Pacific Area Cooperative Telecommunications Network was endorsed at the South Pacific forum.
 * December: David M Hoare appointed Chairman of OTC, following Alan Coates's resignation. The last in a chain of four earth stations in the Antarctic was completed by OTC at Macquarie Island.

1989
 * 1 January: M Hutchinson appointed acting managing director of OTC, following George Maltby's resignation.
 * 1 April: OTC was incorporated and became OTC Limited.
 * 23 June: Australia's first permanent Internet connection is established using OTC facilities. A 56k satellite connection is commissioned between OTC's Oxford Falls Earth Station in Sydney with Sunset Beach Satellite Earth Station in Hawaii. This link provided a connection between University of Melbourne and University of Hawaii. This was also the first usage of TCPIP on a non-private network.
 * July: Steve Burdon appointed managing director of OTC.
 * October: OTC Callcard launched.
 * 28 October the first Intelsat VI launched and placed in orbit over the Atlantic Ocean.
 * November: A direct Australia-UK videoconferencing service opened.

1990s
1990
 * 9 March: New satellite earth station opened in Hanoi.
 * 29 March: OTC International signed its first agreement with island communities in the South Pacific to become members of the Pacific Area Cooperative Telecommunications Network.
 * 6 June: OTC launched its Switched Digital service the first international product based on ISDN technology. The service allowed the high-speed transfer of text, data and images, high-speed facsimile and interactive video and audio.
 * 10 September: Australian Government announced it had finalised plans for a merger between OTC and Telecom.
 * 27 September: New Perth International Telecommunications Centre officially opened.
 * 14 November: Senator Gareth Evans received the inaugural telephone call during the official opening ceremony of the Cambodian earth station in Phnom Penh.
 * 5 December: A Construction and Maintenance Agreement was signed by OTC and 35 other countries in Canberra for the new A$800 million South Pacific optical fibre cable network.

1991
 * 25 January: Commonwealth Telecommunications Interim Board met for the first time. The board was formed by the federal government to advise on the structure of the new telecommunications body which would result from the merger of Telecom and OTC.
 * 6 March: OTC achieved the figure of 1 billion paid minutes of bothway international telephone traffic in one financial year.
 * April: The new OTC Easifax service was launched in Sydney.
 * 15 June: The new Adelaide business office was officially opened.
 * November: The new $12M ISDN exchange at Paddington terminal commenced full operations.
 * 12 November: The shore end of the Tasman 2 optical fibre cable was landed at Bondi Beach.

1992
 * 1 February: OTC ceased operating as a separate company when it merged with Telecom Australia to form the Australian and Overseas Telecommunications Corporation.

title: Overseas Telecommunications Commission