US 6,129,795 A · Metallurgical method for processing nickel- and iron-based superalloys

Abstract

A method is provided for improving the microstructure of nickel and iron-based precipitation strengthened superalloys used in high temperature applications by increasing the frequency of "special", low-.SIGMA. CSL grain boundaries to levels in excess of 50%. Processing entails applying specific thermomechanical processing sequences to precipitation hardenable alloys comprising a series of cold deformation and recrystallization-annealing steps performed within specific limits of deformation, temperature, and annealing time. Materials produced by this process exhibit significantly improved resistance to high temperature degradation (eg. creep, hot corrosion, etc.), enhanced weldability, and high cycle fatigue resistance.

Claims4

Dependent claims

A method for processing a precipitation-hardened austenitic Ni- and Fe-based superalloy to increase the fraction of special low-.SIGMA. grain boundaries as defined herein to a level greater than 50%, while maintaining grain sizes in the range of between 5 .mu.m and 50 .mu.m, comprising:

(i) sequential steps of cold deformation of said superalloy starting material, alternating with steps of annealing the material above its recrystallization temperature;
and
(ii) a final precipitation hardening treatment comprising cold deformation of the superalloy material in the range of from 5% to 10% followed by low-temperature annealing between 700.degree. C and 900.degree. C. for a period of time of up to 16 hours, thereby re-hardening the superalloy material to restore strength.

Dependencies are inferred from the claim text.

Metallurgical method for processing nickel- and iron-based superalloys

Life of this patent

Metallurgical method for processing nickel- and iron-based superalloys

Life of this patent

Abstract

Claims4