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 gamma-matrix with precipitation of gamma ', gamma '' and MC carbides. When heat treated at 750 degrees C for 4 h, gamma '' phase precipitated increasing the hardness by 5%. In situ X-ray observations revealed that heat treating at 870 degrees C for 1 h resulted in delta-phase precipitation. Two different second-stage temperatures were tested (1050 degrees C and 1150 degrees C), which dissolved the delta-phase while MC carbides formed upon cooling. The second stage at 1150 degrees C had a higher deleterious effect than the one performed at 1050 degrees C due to extensive grain growth.