Abstract: A tantalum-containing nickel base superalloy having a .gamma.' phase has greatly improved maximum tensile strength which is substantially independent of the frequency of the stress is processed by forging above the .gamma.' solvus temperature and annealing above the recrystallization temperature of the alloy.

Abstract: A method of supersolvus forging is described for Ni-base superalloys, particularly those which comprise a mixture of .gamma. and .gamma.' phases, and most particularly those which contain at least about 40 percent by volume of .gamma.'. The method permits the manufacture of large grain size forged articles having a grain size in the range of 50-150 .mu.m. The method comprises the selection of a fine-grained forging preform of a Ni-base superalloy. Supersolvus forging in the range of 0.degree.-100.degree. F. above the alloy solvus temperature then performed at slow strain rates in the range of 0.01-0.001 s.sup.-1. Subsequent supersolvus annealing followed by controlled cooling may be employed to control the distribution of the .gamma.', and hence influence the alloy mechanical and physical properties. The method may also be used to produce location specific grain sizes and phase distributions within the forged article.

Abstract: A method is provided for obtaining uniform grain growth within .gamma.' precipitation strengthened nickel-base superalloys provided in powder metal or cast and wrought form. The method includes alloying the nickel-base superalloy to contain a minimum calculated amount of carbon which, when finely dispersed within the alloy using suitable processing methods, yields a sufficient amount of carbide phase which restricts the grain boundary motion of the alloy during supersolvus heat treatment. When appropriately processed, the grains are not permitted to grow randomly during supersolvus heat treatment, making possible a microstructure whose grain size is uniform, having a grain size range of about 2 to about 3 ASTM units and being substantially free of random grain growth in excess of about 2 ASTM units coarser than the desired grain size range.

Abstract: A method is provided for obtaining a uniform grain size on the order of about ASTM 5 or coarser in at least a portion of an article formed from a .gamma.' precipitation strengthened nickel-base superalloy. The method comprises forming an article by: providing a billet, preheating the billet above 2000.degree. F. for at least 0.5 hours, working at least a portion to near-net shape at working conditions including a first strain rate of less than about 0.01 per second and at a subsolvus temperature at or near the recrystallization temperature, supersolvus heating to form a grain size in the portion of at least 5 ASTM, and cooling to reprecipitate .gamma.' within the article. The method can be utilized to form a .gamma.' precipitation strengthened nickel-base superalloy article whose grain size varies uniformly between portions thereof, so as to yield a desirable microstructure and property gradient in the article in accordance with the in-service temperature and stress-state gradient experienced by the article.

Abstract: A method of forging to impart a critical amount of retained strain is described for Ni-base superalloys, particularly those which comprise a mixture of .gamma. and .gamma.' phases, and most particularly those which contain at least about 40 percent by volume of .gamma.'. This forging method harnesses nucleation-limited recrystallization, a phenomenon which has been known in the past to produce uncontrolled, non-uniform Critical grain growth, to produce forged articles having a uniform average grain size in the range of about 90-120 microns. The method comprises the selection of a forging preform formed from a Ni-base superalloy. Isothermal subsolvus forging is then used to form a precursor forging which has a near-net shape. The precursor forging is then forged using relatively high strain rate techniques, such as hammer forging, hot die forging or room temperature forging, to impart all or some portion of it with a critical amount of retained strain energy.

Abstract: A method is provided for obtaining uniform grain growth within .gamma.' precipitation strengthened nickel-base superalloys. The method includes forming a billet having a very fine grain size in order to achieve optimum superplasticity of the superalloy during forging. The article is then heated to a pre-working hold temperature in a manner which prevents coarsening of the microstructure and a loss of superplasticity. The article is then worked, such as by forging, at a temperature below the .gamma.' solvus temperature of the alloy, so as to maintain local strain rates within the article below a critical strain rate for random grain growth, and so as to maintain the strain rate gradient throughout the article below a critical upper limit. After working, the article is subjected to annealing at a temperature which is less than the .gamma.' solvus temperature of the alloy, and for a duration which is sufficient to remove accumulated metallurgical strain in the article.

Abstract: The present invention is directed to a pre-weld overageing heat treatment for nickel-based superalloys, where the alloy is heated to solutionization temperature for a time sufficient to dissolve the gamma prime phase of the alloy microstructure, then slowly cooled with periods of intermittent heating, so that the gamma prime phase reprecipitates as coarse equiaxed particles, and the presence of fine sized gamma prime phase particles is substantially avoided. The present invention is also directed to a welding method wherein said pre-weld overageing treatment is used.

Abstract: The Application relates to a precipitation hardening alloy which has a 0.2% proof stress of at least 500 N/mm.sup.2 and a high resistance to corrosion in highly aggressive sour gas media. The alloy consists of 43 to 51% nickel, 19 to 24% chromium, 4.5 to 7.5% molybdenum, 0.4 to 2.5% copper, 0.3 to 1.8% aluminium and 0.9 to 2.2% titanium, residue iron. Heat treatment processes are described which allow the establishment in the alloy of high strength accompanied by satisfactory ductility.

Abstract: A nickel based superalloy composition is disclosed that provides increased high temperature stress-rupture strength and improved resistance to fatigue crack propagation at elevated temperatures up to about 760.degree. C. The composition is comprised of, by weight percent, about 10% to 12% chromium, about 17% to 19% cobalt, about 1.5% to 3.5% molybdenum, about 4.5% to 6.5% tungsten, about 3.25% to 4.25% aluminum, about 3.25% to 4.25% titanium, about 2.5% to 3,5% tantalum, about 0.02% to 0.08% zirconium, about 0.005% to 0.03% boron, less than 0.1% carbon, and the balance essentially nickel. Thermomechanical processing including isothermal forging at controlled strain rates and temperature ranges, supersolvus annealing, and slow cooling are disclosed for producing an enlarged grain structure that provides the improved properties in the alloy of this invention.

Abstract: Disclosed is a large alloy forging, the forging having an alloy composition selected from one of a nickel base alloy, a cobalt-chromium-nickel base alloy, a nickel-cobalt base alloy and an iron-nickel-chromium-molybdenum alloy, the forging having a grain size of ASTM grain size 3 or finer, as measured by ASTM method E112 and having a tensile strength in the range of 135 to 175 KSI.

Abstract: Disclosed is a large alloy forging and method for making it. The forging having an alloy composition selected from one of a nickel base alloy, a cobalt-chromium-nickel base alloy, a nickel-cobalt base alloy and an iron-nickel-chromium-molybdenum alloy and having a grain size of ASTM grain size 4 or finer, as measured by ASTM method E112 and having a tensile strength in the range of 135 to 175 KSI. The process includes: (1) four upset forgings, (2) a rapid cooling after the final upset cooling, (3) a first and second upset forging with a reduction greater than 50%, (4) a third upset forging with a reduction greater than 25.%, and (5) a forging process with a fourth upset forging with a reduction greater than 50%.

Abstract: A method of increasing intergranular stress corrosion cracking resistance of Alloy 718 in water reactor environments is described where the alloy is heat treated at a high solution annealing temperature to dissolve grain boundary precipitates formed during thermomechanical processing. A water quenching step is advantageously employed following the high solution annealing. The alloy is then aged at two separate temperatures and finally air cooled to room temperature.

Abstract: The object of the present invention is to provide a method for the manufacturing of a cutting material possessing excellent toughness and a high strength. The composition by weight of the Nickel alloy ingot, is chromium (Cr )14-23%, molybdenum (Mo) 14-20%, tungsten (W) 0.2-5%, iron (Fe) 0.2-7%, cobalt (Co) 0.2-2.5% with the remaining portion being made up of Ni and unavoidable impurities. After undergoing a solution heat treatment process, the Ni ingot undergoes plastic working, at a product ratio above 80%, followed by heating at a temperature of 500.degree.-600.degree. C. for longer than 30 minutes. Heating the alloy of the aforementioned composition at the above mentioned temperature promotes the precipitation of an intermetallic compound possessing a hardness greater than 57 on the HRC. The resulting superior cutting material is resistant to corrosion even when exposed to sea water.

Abstract: A high strength lead frame material consists essentially, by weight, of 0.5 to 22% Co, 22 to 32.5% Ni, not more than 1.0% Mn and not more than 0.5% Si and the balance Fe and incidental impurities. The contents of Ni and Co are selected so that the Ni content is 27 to 32.5% when the Co content is less than 12%, and so that, when the Co content is not less than 12%, the Ni content and the Co content meet the condition of 66%.ltoreq.2Ni+Co.ltoreq.74%. The material has a multi-phase structure formed of austenitic phase, martensitic phase, and ferritic phase, the austenitic phase occupying not less than 50% of the structure.The method of producing the alloy of the invention comprises the steps of solid-solutioning the material of the above composition at a temperature not less than austenitizing completion temperature, cold-rolling the material at a rate of 40 6to 90% in reduction, and annealing the material at a temperature less than the austenitizing completion temperature.

Abstract: A method of forming a Ni-base superalloy suitable for use as the material for gas turbine disks or the like has a composition containing, by weight, 0.01 to 0.15% of C, 15 to 22% of Cr, 3 to 6% of Mo, 3 to 6% of W, 5 to 15% of Co, 1.0 to 1.9% of Al, 1.5 to 3.0% of Ti, 3.0 to 6.0% of Ta, 0.001 to 0.020% of B and the balance substantially Ni except inevitable impurities. This alloy is produced using the conventional ingot making and a hot working process including working at a reducing ratio greater than or equal to 10%, first above the .gamma. solvus temperature, and then during cooling to the recrystallization temperature and then subjected to direct aging without solid-solution treatment. As a result, the alloy exhibits excellent strength properties well comparable to those of expensive alloys produced by powder metallurgy process.