Enhancing tensile and creep properties of Inconel 617 superalloy via regulating the synergistic evolution of M23C6 carbides and γ′ phases

Abstract

A novel heat treatment strategy, termed solution-double aging treatment (SDAT), is proposed to enhance the tensile properties and creep resistance at high-temperature of Inconel 617 Ni-based superalloy. This method aims to achieve a microstructure that maintains excellent thermal stability at elevated temperature up to 760 °C. The results suggest that the improved tensile properties of SDAT-treated alloys are attributable to orderly precipitation and synergistic interaction of M₂₃C₆ carbides and γ′ phases. Under identical creep conditions, SDAT alloys significantly enhance creep strength and extend creep rupture life in comparison to solution-treated (ST) alloys. Specifically, under creep conditions of 760 °C/170 MPa, SDAT alloys exhibit a 37.25 % longer creep rupture life than ST alloys, particularly under low-stress conditions. The enhanced creep properties of SDAT alloys are due to the unique microstructure produced by the SDAT treatment: the high-density and small-size of γ′ phases effectively impede dislocation movement, thereby reducing the minimum creep rate; the evolution of cylindrical coarse M₂₃C₆ carbides predominantly occurs near grain boundaries or within grains, reducing the formation of creep cracks; the high proportion of grain boundary M₂₃C₆ carbides mitigates creep damage caused by carbide evolution, inhibiting the initiation and extension of grain boundary cracks. The SDAT heat treatment process provides a novel approach to improving the creep life of Ni-based superalloys by controlling the synergistic evolution mechanisms of carbides and γ′ phases.