General Electric Company

Keh-Minn Chang

Shyh-Chin Huang

Alan I Taub

Jeffrey Francis Wessels

Daniel D Krueger

Swami Ganesh

Richard G Menzies

Sulekh C Jain

Bruce P Bardes

Michael E Sauby

Ioannis P Vasatis

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.

Supersolvus processing for tantalum-containing nickel base superalloys

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.

High-temperature fatigue-resistant nickel based superalloy and

A dual alloy disk made from a rim alloy having high stress rupture and creep resistance as well as good hold time fatigue crack resistance and a hub alloy having high tensile strength and good low cycle fatigue crack resistance is described. The dual alloy disk is designed for use as a disk in gas turbine engines operating as high as 1500.degree. F. The hub and rim are joined together at a substantially defect-free joint to form a turbine disk having improved properties in both the hub and rim regions.

Dual alloy turbine disk

A method of improving the low temperature ductility of an iron-aluminide is taught. The aluminide for which the method is applicable is one having between 30 and 50 atom percent of aluminum. The aluminide may also have substituents for part of the iron and for the aluminum. The alloy may contain up to 10 atom percent of substituents for the iron selected from the group of metals comprising nickel cobalt chromium and manganese. The alloy may also contain substituents for the aluminum of up to 5 atom percent of a metal selected from the group comprising titanium, niobium, tantalum, hafnium, zirconium, vanadium, and silicon. The alloy has a B2 crystal structure. The first step of the process is to select the metal to be processed. The next step is to directionally solidify the selected metal. The next step is to determine the Ductile Brittle Transition Temperature (DBTT). The metal is then heated to above the DBTT and is deformed while above the DBTT temperature. As a result of this treatment the ductility of the alloy is greatly improved.

Method for improving low temperature ductility of directionally

Improved, creep-stress rupture and hold-time fatigue resistant nickel base alloys for use at elevated temperatures are disclosed. The alloys consists essentially of, in weight percent, 10.9 to 12.9% Co; 11.8 to 13.8% Cr; 4.6 to 5.6% Mo; 2.1 to 3.1% Al; 4.4 to 5.4% Ti; 1.1 to 2.1% Nb; 0.005 to 0.025% B; 0.01 to 0.06% C; 0 to 0.6% Zr; 0.1 to 0.3% Hf; balance nickel. The article is characterized by a microstructure having an average grain size of from about 20 to 40 microns, with carbides, borides, and 0.3 to 0.4 micron-sized coarse gamma prime located at the grain boundaries, and 30 nanometer-sized fine gamma prime uniformly distributed throughout the grains. The alloys are suitable for use as turbine disks in gas turbine engines of the type used in jet engines, or for use as rim sections of dual alloy turbine disks for advanced turbine engines and are capable of operation at temperatures up to about 1500.degree. F. A method for achieving the desired properties in such turbine disks is also disclosed.

Creep, stress rupture and hold-time fatigue crack resistant alloys

An alloy is disclosed which has been found to lend itself particularly well to thermomechanical processing. The alloy is strengthened by precipitates similar to those of Inconel 718 but the alloy matrix of the composition is a nickel-chromium-cobalt matrix rather than the nickel-chromium-iron matrix of the Inconel alloy. Also the alloy has grains of average diameter of 35 .mu.m or larger. The fatigue resistance, tensile strength and the rupture strength of the alloy is improved to a remarkable degree as a result of the thermomechanical processing. The thermomechanical processing is carried out below the recrystallization temperature to prevent nucleation of fine grains. The residual strains from the thermomechanical processing or cold working provides the remarkably favorable combination of alloy properties which are found.

Fatigue crack resistant nickel base superalloy

Thermomechanical processing treatments for powder compacts formed from powdered superalloy compositions having a volume fraction of gamma prime greater than 35 percent are disclosed. Isothermal forging within critical ranges of strain rate and temperature is followed by supersolvus annealing and slow cooling treatments. An enlarged grain structure about 50 to 60 microns in size is produced that improves resistance to fatigue crack propagation in the superalloys.

Thermomechanical processing for fatigue-resistant nickel based

A low-alloy steel suitable for use in generator rotors and having a combination of good strength and impact energy with a high magnetic permeability is disclosed. The low-alloy steels are comprised of in weight percent; about 3.5 to 5.25 percent nickel, about 0.75 to 2.0, percent chromium, about 0.3 to 0.8 percent molybdenum, about 0.05 to 0.15 percent vanadium, about 0.1 to 0.28 percent carbon, about 0.03 to 0.1 percent niobium or titanium, and the balance substantially iron, wherein nickel, chromium, and carbon additions are balanced.

Generator rotor steels

Alloy compositions for nickel-base superalloys having the qualities of weldability, castability and forge-ability together with improved high temperature strength and rupture properties are disclosed. The weldability is improved by varying the Al, Ti, Nb and Ta content so as to insure that only the favorable .gamma.' precipitates are formed in the alloy. The high temperature properties of the alloy compositions are optimized by controlling the content of the major alloying elements Co and Cr. Preferably the alloy is substantially free of Fe.

Nickel-base superalloy systems

This invention relates to corrosion resistant, austenitic, non-magnetic alloys. The alloys contain about 32 to 38% nickel, about 3 to 7% chromium, about 3 to 5% titanium, about 0.3 to 1.5% aluminum, about 0.5 to 1.5% molybdenum, an effective amount of vanadium, about 0.005 to 0.02% boron, up to about 0.02% carbon, and the balance substantially iron. The alloys are controlled temperature hot rolled and age annealed to provide strain hardening and precipitation strengthening to achieve yield strength objectives established for retaining rings in new high capacity generators. Yield strengths of at least about 200 ksi can be produced by the alloys of this invention making them suitable for use in new high capacity generators.

High strength non-magnetic alloy

A novel alloy is provided having approximately the following ingredient formula:

Method of forming strong fatigue crack resistant nickel base superalloy

A novel nickel base superalloy is provided. The alloy is unique in having a high enough concentration of .gamma.' strengthening precipitate to provide a valuable set of physical properties and yet retain forgeability properties similar to those of alloys having lower concentration of precipitate.

Method of forming fatigue crack resistant nickel base superalloys and

A novel heat treatment of a disk for a jet engine is provided. A temperature gradient is established on the disk to heat the inner portions to a temperature at which a subsolvus anneal takes place and to heat the outer portions to a temperature where a supersolvus anneal takes place. A reverse gradient is established from the inner portions of the disk during cooling after the anneal to cool the inner portions of the disk more rapidly than the outer portions so as to impart high tensile and fatigue strength to the inner portions and high temperature rupture life and crack growth resistance to the outer portions. A novel disk results.

Method of making high strength superalloy components with graded

A method is provided for reducing fatigue crack propagation in nickel base superalloys. The method involves a supersolvus anneal in which essentially all .gamma.' precipitate phase is dissolved. The supersolvus anneal is folloed by slow cooling which is at a rate which substantially reduces time dependent fatigue crack growth but which preserves the strength of the alloy at a useful level for many superalloy applications.

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Schenectady, NY, United States of America

Keh-Minn Chang