Gleeble simulation of the HAZ in Inconel 617 welding

Five kinds of thermal cycle, with different peak temperatures ranging between 1150 °C and 1350 °C were taken to simulate HAZs with same heating and cooling rate. The microstructure of different simulated HAZs was characterized by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The micro-hardness, grain size and tensile test at 750 °C of simulated HAZs were conducted. Coarsened carbides along the grain boundaries are observed in the HAZs simulated at 1200 °C and 1250 °C. For the HAZs simulated at 1300 °C and 1350 °C, the carbides inside grains vanish, and continuous lamellar structure occurs at the grain boundaries. The microstructure of HAZ simulated at 1150 °C is similar to that of base metal (BM). The micro-hardness and average grain size of simulated HAZs have no obvious variation compared to the BM. Tensile test results show that the yield stress (YS) and ultimate tensile stress (UTS) decrease as simulation peak temperature increases, which attributes to the coarsened carbides and continuous lamellar structure occurring at the grain boundaries at higher temperature.