General Electric Company

Allen J Paxson

Robert D Kissinger

Eric Scott Huron

Edward Lee Raymond

Clifford Earl Shamblen

Richard G Menzies

Michael E Sauby

A .gamma.' precipitation strengthened nickel-base superalloy provided in powder metal or cast and wrought form and alloyed to minimize nucleation tendencies and control grain growth. The superalloy includes a fine dispersion of a second phase in sufficient amounts to prevent critical grain growth in the superalloy when the superalloy is subjected to temperatures above its .gamma.' solvus temperature. The superalloy preferably contains at least about 0.030 weight percent carbon or about 27 to about 2000 ppm yttrium in order to produce a volume fraction of the second phase which is sufficient to cover a minimum of about 10 percent of the grain boundary area. The fine dispersion of the second phase restricts the grain boundary motion of the alloy during supersolvus heat treatment, thereby preventing random grain growth during supersolvus heat treatment and yielding a microstructure whose grain size is uniform, for example, 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.

Nickel-base superalloy having improved resistance to abnormal grain

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.

Method for forming a nickel-base superalloy having improved resistance

Fatigue crack growth-resistant articles are made from powder metal or cast and wrought gamma prime precipitation strengthened nickel-base superalloy material, wherein a relatively high predetermined minimum strain rate, .epsilon..sub.min, is employed during hot working at or near the alloy's recrystallization temperature; or alternatively a relatively high strain level, .epsilon..sub.min, is employed during cold or warm working at temperatures below the alloy's recrystallization temperature. The worked articles are characterized by a uniform fine grain size, and grains which coarsen uniformly after heating at the supersolvus solutioning temperature, thereby alleviating non-uniform grain growth within the material.

Method for making fatigue crack growth-resistant nickel-base article

A titanium alloy billet having improved response to ultrasonic inspection is described. The billet is given a thermomechanical treatment above the beta transus of the alloy immediately prior to ultrasonic inspection. The treatment may include beta annealing or mechanical deformation above the beta transus. The invention is particularly effective for beta-stabilized alpha-beta and beta titanium alloys.

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Cincinnati, OH, United States of America

Allen J Paxson