EFFECT OF PRODUCTION ROUTE ON THE STRUCTURE AND PROPERTIES OF A NICKEL-CHROMIUM-COBALT ALLOY

Abstract

Preparation of an extruded nickel-chromium-cobalt alloy of the Nimonic 90 type, using powders, wires, and conventional cast billets as starting materials, resulted in a wide variety of grain sizes and structures. The form of the oxide/carbide and its distribution varied with the production route. The performance of the materials, as assessed by stress-rupture, fatigue, and impact data, also differed considerably. The stability of the grains was directly related to the distribution of the oxides/carbides and was therefore interrelated to the stress-rupture properties. Fatigue properties were sensitive to a fine general distribution of oxides/carbides and impact properties were sensitive to an intergranular distribution. With the best structure, of a fibrous nature, it was possible to achieve an attractive combination of stress-rupture, fatigue, and impact properties—the last being unusually high.