Interfacial characteristics and residual welding stress distribution of K4750 and Hastelloy X dissimilar superalloys joints

Abstract

Gas tungsten arc welding (GTAW) method was employed to join a newly developed cast superalloy K4750 with Hastelloy X by using K4750 and Hastelloy X filler metals (FMs), respectively. Thereby we obtained two kinds of interfaces namely K4750 base metal (BM) and Hastelloy X FM, and K4750 FM and Hastelloy X BM. The elemental distribution, interfacial characteristics, and the residual welding stress of the dissimilar joints were investigated by electron probe micro analyzer (EPMA), electron backscattered diffraction (EBSD), and section technique, respectively. The results showed that the elemental distribution across both interfaces were varied significantly. And the composition segregation regions were identified in both interfaces but the segregation extent was different. Epitaxial growth was clearly observed in both interfaces. The distribution of the residual welding stress across the joint exhibited that the highest tension stress area in both as-welded joints was located at the joint heat affected zone (HAZ). The residual welding stress in the joint with Hastelloy X FM was significantly relieved through post weld heat treatment (PWHT).