Abstract: A damage tolerant microstructure for a lamellar alloy, such as a lamellar ?TiAl alloy, is provided in accordance with the present invention. The alloy comprises a matrix and a plurality of grains or lamellar colonies, a portion of which exhibit a nonplanar morphology within said matrix. Each of the lamellar colonies contains a multitude of lamella with irregularly repeating order. The ?TiAl platelets have a triangular (octahedral) unit cell and stack with ? twins. The ?2Ti3Al platelets are irregularly interspersed. The unit cell for ?2Ti3Al is hexagonal. Each of the layers has a curved, nonplanar structure for resisting crack formation and growth.

Abstract: A damage tolerant microstructure for a lamellar alloy, such as a lamellar ?TiAl alloy, is provided in accordance with the present invention. The alloy comprises a matrix and a plurality of grains or lamellar colonies, a portion of which exhibit a nonplanar morphology within said matrix. Each of the lamellar colonies contains a multitude of lamella with irregularly repeating order. The ?TiAl platelets have a triangular (octahedral) unit cell and stack with ? twins. The ?2Ti3Al platelets are irregularly interspersed. The unit cell for ?2Ti3Al is hexagonal. Each of the layers has a curved, nonplanar structure for resisting crack formation and growth.

Abstract: The present invention relates to an improved single crystal nickel base superalloy and a process for making same. The single crystal nickel base superalloy has a composition comprising 3 to 12 wt % chromium, up to 3 wt % molybdenum, 3 to 10 wt % tungsten, up to 5 wt % rhenium, 6 to 12 wt % tantalum, 4 to 7 wt % aluminum, up to 15 wt % cobalt, up to 0.05 wt % carbon, up to 0.02 wt % boron, up to 0.1 wt % zirconium, up to 0.8 wt % hafnium, up to 2.0 wt % niobium, up to 1.0 wt % vanadium, up to 0.7 wt % titanium, up to 10 wt % of at least one element selected from the group consisting of ruthenium, rhodium, palladium, osmium, iridium, platinum, and mixtures thereof, and the balance essentially nickel. The single crystal nickel base superalloy has a microstructure which is pore-free and eutectic ?–?? free and which has a gamma prime morphology with a bimodal ?? distribution.

Abstract: A damage tolerant microstructure for a lamellar alloy, such as a lamellar ?TiAl alloy, is provided in accordance with the present invention. The alloy comprises a matrix and a plurality of grains or lamellar colonies, a portion of which exhibit a nonplanar morphology within said matrix. Each of the lamellar colonies contains a multitude of lamella with irregularly repeating order. The ?TiAl platelets have a triangular (octahedral) unit cell and stack with ? twins. The ?2Ti3Al platelets are irregularly interspersed. The unit cell for ?2Ti3Al is hexagonal. Each of the layers has a curved, nonplanar structure for resisting crack formation and growth.

Abstract: A damage tolerant microstructure for a lamellar alloy, such as a lamellar &ggr;TiAl alloy, is provided in accordance with the present invention. The alloy comprises a matrix and a plurality of grains or lamellar colonies, a portion of which exhibit a nonplanar morphology within said matrix. Each of the lamellar colonies contains a multitude of lamella with irregularly repeating order. The &ggr;TiAl platelets have a triangular (octahedral) unit cell and stack with &ggr; twins. The &agr;2Ti3Al platelets are irregularly interspersed. The unit cell for &agr;2Ti3Al is hexagonal. Each of the layers has a curved, nonplanar structure for resisting crack formation and growth.

Abstract: The present invention relates to an improved single crystal nickel base superalloy and a process for making same. The single crystal nickel base superalloy has a composition comprising 3 to 12 wt % chromium, up to 3 wt % molybdenum, 3 to 10 wt % tungsten, up to 5 wt % rhenium, 6 to 12 wt % tantalum, 4 to 7 wt % aluminum, up to 15 wt % cobalt, up to 0.05 wt % carbon, up to 0.02 wt % boron, up to 0.1 wt % zirconium, up to 0.8 wt % hafnium, up to 2.0 wt % niobium, up to 1.0 wt % vanadium, up to 0.7 wt % titanium, up to 10 wt % of at least one element selected from the group consisting of ruthenium, rhodium, palladium, osmium, iridium, platinum, and mixtures thereof, and the balance essentially nickel. The single crystal nickel base superalloy has a microstructure which is pore-free and eutectic &ggr;-&ggr;′ free and which has a gamma prime morphology with a bimodal &ggr;′ distribution.

Abstract: Compositional requirements and processing improvements are disclosed which improve the hydrogen embrittlement resistance and the fatigue resistance in air of nickel base single crystal articles. The compositional requirements enlarge the difference between the &ggr;′ solvus temperature and the incipient melting temperature, thus enabling the solution of &ggr;/&ggr;′ eutectic islands without causing incipient melting, while hot isostatic pressing and careful melt practice eliminate porosity and carbides, borides and nitrides, all of which act as crack initiation sites.

Abstract: A nickel base superalloy, having either columnar or equiaxed grain structure, which has significantly improved resistance to hydrogen embrittlement, and to fatigue in air. The material is processed so as to be essentially free of script type carbides, .gamma./.gamma.' eutectic islands and porosity. The processing includes heat treating above the .gamma.' solvus temperature to solution the script type carbides and eutectic islands, followed by HIP to eliminate the porosity.

Abstract: Columnar grain and single crystal nickel base superalloys are heat treated to provide a damage tolerant microstructure. The microstructure contains large, irregularly shaped "barrier" .gamma.' particles interspersed in an ordered array of smaller cuboidal .gamma.' particles in a .gamma. phase matrix. The barrier particles interrupt the progression of cracks through the microstructure. The invention process includes solutioning the .gamma.' phase, cooling slowly to a temperature about 50.degree. F. to 150.degree. F. (28.degree. C. to 83.degree. C.) below the .gamma.' solvus temperature, further cooling at a rate of at least about 100.degree. F. (56.degree. C.) per minute to less than 1000.degree. F. (538.degree. C.), reheating to 1975.degree. F. to 2000.degree. F. (1079.degree. C. to 1093.degree. C.) and holding for about four to six hours, cooling at 100.degree. F. (56.degree. C.) per minute to less than 1000.degree. F. (538.degree. C.), and heating to 1600.degree. F..+-.25.degree. F. (871.degree. C..+-.14.

Abstract: A nickel base superalloy, having either columnar or equiaxed grain structure, which has significantly improved resistance to hydrogen embrittlement, and to fatigue in air is disclosed. The superalloy consists essentially of, in weight percent, about 0.006-0.17 carbon, about 6.0-22.0 chromium, up to about 17.0 cobalt, up to about 9.0 molybdenum, up to about 12.5 tungsten, up to about 5.0 titanium, up to about 6.7 aluminum, up to about 4.5 tantalum, up to about 2.5 hafnium, up to about 18.5 iron, up to about 3.25 rhenium, up to about 1.25 columbium, remainder nickel. The microstructure of the superalloy consists essentially of a plurality of fine, discrete carbide particles, .gamma.' precipitates in a .gamma. matrix, and is essentially free of script carbides, .gamma./.gamma.' eutectic islands and porosity.

Abstract: The present invention relates to a method for making a gamma prime precipitation strengthened nickel base alloy having an improved resistance to hydrogen embrittlement, particularly crack propagation. The alloy is cast, heat treated to dissolve substantially all the gamma-gamma prime eutectic islands and script carbides without causing incipient melting, cooled to below 1000.degree. C., HIP'ed to eliminate porosity, precipitation treated and aged. The alloy has a microstructure which is essentially free of script carbides, gamma-gamma prime eutectic islands and porosity. The microstructure further includes a plurality of regularly occurring large barrier gamma prime precipitates and a continuous field of fine cuboidal gamma prime precipitates surrounding the large barrier gamma prime precipitates.

Abstract: The present invention relates to a heat treated, gamma prime precipitation strengthened nickel base alloy having an improved resistance to hydrogen embrittlement, particularly crack propagation. The alloy has a microstructure which is essentially free of script carbides, gamma--gamma prime eutectic islands and porosity. The microstructure further includes a plurality of regularly occurring large barrier gamma prime precipitates and a continuous field of fine cuboidal gamma prime precipitates surrounding the large barrier gamma prime precipitates.

Abstract: The present invention relates to a .gamma." strengthened nickel based alloy having an improved resistance to hydrogen embrittlement and to a process for forming the same. The nickel based alloy consists essentially of from about 0.02 to 0.06 wt % carbon, from about 11 to 13 wt % chromium, from about 17 to 19 wt % iron, from about 2.80 to 3.30 wt % molybdenum, from about 5.75 to about 6.25 wt % columbium+tantalum, from about 1.75 to 2.25 wt % titanium, from about 0.4 to 0.8 wt % aluminum and the balance essentially nickel and is in single crystal form. The nickel based alloy of the present invention has particular utility in high pressure hydrogen environments such as rocket engine components.

Abstract: Columnar grain and single crystal nickel base superalloys are heat treated to provide a damage tolerant microstructure. The microstructure contains large, irregularly shaped "barrier" .gamma.' particles interspersed in an ordered array of smaller cuboidal .gamma.' particles in a .gamma. phase matrix. The barrier particles interrupt the progression of cracks through the microstructure. The invention process includes solutioning the .gamma.' phase, cooling slowly to a temperature about 50.degree. F. to 150.degree. F. (28.degree. C. to 83.degree. C.) below the .gamma.' solvus temperature, further cooling at a rate of at least about 100.degree. F. (56.degree. C.) per minute to less than 1000.degree. F. (538.degree. C.), reheating to 1975.degree. F. to 2000.degree. F. (1079.degree. C. to 1093.degree. C.) and holding for about four to six hours, cooling at 100.degree. F. (56.degree. C.) per minute to less than 1000.degree. F. (538.degree. C.), and heating to 1600.degree. F. .+-.25.degree. F. (871.degree. C. .+-.14.