Tensile and creep-rupture response of additively manufactured nickel-based superalloy CM247LC

Abstract

Tensile and creep rupture properties of crack-free CM247LC alloy, processed via laser powder bed fusion, have been characterised in this work at temperatures up to 1000°C. The subject alloy matches or even exceeds the tensile performance of its directionally solidified counterpart up to 700°C, beyond which both the strength and ductility drop off relatively rapidly with increasing temperature. It was found that the agglomeration of discrete carbides – that essentially pin the grain boundaries – facilitate the nucleation, linking and propagation of microcracks along the adjacent grain boundaries at elevated temperatures. Relatively short-term creep-rupture tests conducted at 800°C show the need for greatly improving the microstructure of this alloy to compete with its directionally solidified or conventionally cast counterparts, especially considering that this material finds extensive application up to ∼950°C in turbomachinery components. Increasing the grain size, incorporating grain boundary engineering concepts and a better understanding of carbide/γ' precipitate evolutionary characteristics can greatly help to improve the material's suboptimal creep response.

Keywords

• Additive manufacturing
• L-PBF CM247LC
• Nickel superalloy
• Tensile properties
• Creep
• Microstructure