An alternative approach to processing dispersion-stabilized superalloys

Abstract

A possible simpler, more direct, more reproducible and less expensive method for processing nickel-base oxide-dispersion-stabilized alloys is described. The process calls for melting or remelting of fully alloyed master alloys and then atomizing to produce a high yield of fully alloyed, rapidly solidified fine powders, ideally finer than about 44–60 μm. The fine powders are attrited to flakes nearly a micron thick in a protective fluid, followed by ball milling in an inert atmosphere to blend in very fine refractory oxide particles. Excellent dispersion of the oxides is obtained. After consolidation by hot extrusion, direcitonally recrystallized coarse grains with a 〈100〉 fiber texture and high grain aspect ratio are produced using a solid state crystal-growing zone-aligned polycrystal (ZAP) process. The stress rupture strength of the ZAP superalloy product is twice that of the same alloy given a conventional recrystallization heat treatment and about four times that of the as-extruded material. The application of this technique to both solid solution and precipitation-strengthened oxide-dispersed alloys is discussed.