Carbide dissolution and grain growth behavior of a nickel-based alloy without γ′ phase during solid solution

Abstract

In this paper, a new type of non-γ′ phase nickel-based heat-resistant alloy C-HRA-2 was studied by solution heat treatment. It was determined that after removing the γ′ phase, the carbide dissolution temperature was reduced and the grain growth process of nickel-based alloy was accelerated. It was also determined that the dissolution of M23C6 carbides is attributable to a gradual decomposition and diffusion process. High-temperature confocal scanning laser microscopy (HT-CLSM) was utilized to simulate the grain growth of the alloy during the solid solution treatment. The results revealed that only a portion of the grain boundaries migrated simultaneously, while most of the migration directions and distances followed the classical migration theory. Some grain boundaries expanded into new grain boundaries via sub-crystal rotation during grain growth. Following solution heat treatment, the yield strength of the alloy was mainly attributed to solution strengthening and grain boundary strengthening. The solution strengthening was found to be approximately 230 MPa and the grain boundary strengthening was found to be approximately 37–118 MPa. Carbides increase the precipitation strengthening of the alloy during dissolution.