Effect of heat treatments on Inconel 625 fabricated by wire and arc additive manufacturing: an in situ synchrotron X-ray diffraction analysis

The effect of heat treatments on wire and arc additively manufactured Inconel 625 parts was investigated using in situ synchrotron X-ray diffraction and hardness testing. As-built samples revealed the presence of a γ-matrix with precipitation of γ′, γ′′ and MC carbides. When heat treated at 750°C for 4 h, γ′′ phase precipitated increasing the hardness by 5%. In situ X-ray observations revealed that heat treating at 870°C for 1 h resulted in δ-phase precipitation. Two different second-stage temperatures were tested (1050°C and 1150°C), which dissolved the δ-phase while MC carbides formed upon cooling. The second stage at 1150°C had a higher deleterious effect than the one performed at 1050°C due to extensive grain growth.