Effect of Micro Plasma Arc Welding Variables on the Microstructure, Mechanical Properties and Electrical Resistance of 80Ni-20Cr Heating

In this investigation، effects of micro plasma arc welding variables (such as: welding current and pulsation)، on the microstructure، mechanical properties، and electrical resistance of 80Ni-20Cr heating alloy have been studied. The 2 mm diameter wires were used as the base metal and welded at various conditions. The Optical Microscopy (OM)، Scanning Electron Microscopy (SEM)، tensile test، microhardness test، and electrical resistance test were performed to evaluate microstructural، mechanical properties، and electrical resistance of the welds. The OM and SEM examinations show that weld metal in all samples had equi-axed grains. Grains and carbides size (Cr23C6 and TiC) both increased by increasing of welding current. The tensile and microhardness results showed، a decrease with increasing the grains size، and carbides size. In addition، at constant welding currents، with applying pulsation، higher tensile strength and hardness were obtained. The electrical resistance results showed، that electrical resistance of welded joints depends on the grains size and carbides distribution. The lowest electrical resistance was obtained at the welding current of 10 A in pulsation mode.