Joining phenomena and tensile strength of joint between Ni-based superalloy and heat-resistant steel by friction welding

Abstract

In order to obtain easily good joint with no crack at the interface between Ni-based superalloy (Ni-SA) and heat-resistant steel (HRS), the investigation of weldability in those material combinations by friction welding method is required. This paper described the joining phenomena and the tensile strength of the friction-welded joint between Ni-SA and HRS. The joining phenomena during the friction process, such as joining behaviour and friction torque, were measured. The effects of friction pressure, friction time, and forge pressure on the joint tensile strength were also investigated, and the characteristics of joints were observed and analysed. The good joint, which had the fracture in the HRS base metal and the tensile strength of its base metal with no crack at the weld interface, could be successfully achieved, although it had the hardened and softened areas at the adjacent region of the weld interface. In conclusion, it was found that the joint should be made with an opportune friction time after the HRS side was transferred to the entire weld interface on the Ni-SA side and with adding high forge pressure such as 360 MPa. Hence, the good joint could be obtained by friction welding method.