Recent developments in cobalt base alloys

Abstract

Cobalt base alloys are being developed to produce the best possible combinations of high temperature properties. Existence of martensite forms consisting of various intermetallic compounds has been described along with the variables associated with fcc-hcp transition at respective conditions of formation. Achievements of cobalt base alloys have been primarily due to various thermodynamic and kinetic parameters for most suitable combinations of alloying. The phase transformations in this review include the study of defect structure, martensite transformation, order-disorder kinetics, and recrystallization and grain growth mechanisms. The improvements in mechanical properties stem from the contribution of additional alloying elements to discontinuous precipitation, diffusion mechanism at grain boundaries and changes in compressive strength, yield strength, elongation and brittleness. L12-compound in cobalt base alloys possesses an important identity, which changes the characteristics of usable compositions.