Patent ID: 7507306

Claim:
A method of processing a nickel-iron-chromium alloy, the method comprising the steps of: preparing a melt of the alloy, the alloy containing about 32 to about 38 weight percent iron, about 22 to about 28 weight percent chromium, about 0.05% to about 0.5% aluminum, at least 0.12% to about 0.30% carbon, and a sufficient amount of titanium, zirconium, and nitrogen so that titanium and zirconium carbonitride precipitates formed thereby and having the formula [(Ti x Zr 1-x )(C y N 1-y )] are near their solubility limit in the melt and so that carbon and nitrogen are present in a carbon:nitrogen weight ratio of at least 1:2 to 1:1; forming an ingot of the alloy, during which the carbon:nitrogen weight ratio minimizes the precipitation of carbides and nitrides and promotes the formation of a dispersion of fine titanium and zirconium carbonitride precipitates in the ingot; thermomechanically working the alloy during which the titanium and zirconium carbonitride precipitates inhibit austenitic grain growth; solution heat treating the article during which the titanium and zirconium carbonitride precipitates remain present and inhibit austenitic grain growth; and then quenching the article, the article containing the dispersion of fine titanium and zirconium carbonitride precipitates.