Investigating the Effect of Current Type (Direct and Pulsed) on Microstructure and Mechanical Properties of Hastelloy B-2 Superalloy Welded Joint by GTAW Process

In this research, Gas tungsten arc welding (GTAW) on Hastelloy B-2 Superalloy was used to investigate the effect of current type on microstructure and mechanical properties of welded zone. The welding process was performed using two direct and pulsed current and with Hastelloy X filler metal. Optical Microscope (OM) and Scanning Electron Microscope (SEM) were used to investigate the microstructure and Energy Dispersive X-ray Spectroscopy (EDS) was used to analysis the precipitations. The microscopic observation showed that applying pulsed current led to a significant reduction in the size of the dendrites and microstructure in the weld metal. Hardness results showed that with direct current the hardness of weld metal is 300 Vickers while with pulsed current hardness is 330 Vickers. In the tensile test, all samples were fractured softly from the base metal. Also, the specimen welded with pulsed current has better tensile properties (elongation %50, yield strength 434 MPa and  ultimate tensile strength 660 MPa).