Creep behaviour and life assessment of a cast nickel - Base superalloy MAR - M247

Abstract

The cast nickel-base MAR-M247 superalloy has been widely used for high-temperature components. In this work, the creep behaviour of two alternates of MAR-M247 superalloy with different grain size processed at different temperatures of casting are compared. Under the creep testing conditions used in this study, only negligible differences of creep behaviour of the alternate alloys were found and the evaluated creep characteristics correspond to the power-law or dislocation creep. The microstructure of the alloys consists of a matrix with a eutectic, strengthening cubic precipitates, and M6C and M23C6 carbides. Increasing the temperature induces the dissolution of some M23C6 carbides. Fractures of both variants of alloys exhibit a more ductile character at higher temperatures, while at lower temperature a mixture of brittle and ductile fracture modes was observed, which changes the creep fracture ductility.