Impulse Capacitor Discharge Welding of Hollow Structure Made of Nickel-Base Alloy

Future steam turbines will use hollow structures so that the turbine inlet temperature can be increased to improve the thermal efficiency. These hollow structures are made of the nickel-base alloy Nicrofer 6025 HT and consist of a wire mesh between two cover sheets. The cover sheets can be joined to the wire mesh by capacitor discharge welding due to its extremely short welding duration. The goal of this research is to investigate suitable welding parameters so that the weld spots form in an optimum way to increase the tensile shear strength and reduce spattering. Tensile shear tests, three-point bending tests, and micrographs were used to judge the joint quality of structures made with various welding parameters. The results show that the best welds are obtained with a transmission ratio of 1:200, welding energy of 70% to 95%, and electrode force of 7 to 9 MPa.