Microstructural and Mechanical Characterization of Welded Joints between Stainless Steel and Hastelloy Made Using Pulsed Current Gas Tungsten Arc Welding

Austenitic stainless steel (ASS) grade is considered to be alternative material for Hastelloy C-276, due to its higher material and maintenance cost. Hence, the combination of joining the ASS and Hastelloy C-276 is advisable. In this investigation, Hastelloy C276 and 316L stainless steel materials were joined as similar weld of stainless steel 316 L and Hastelloy C276, as well as dissimilar joints between the Hastelloy C276 and 316L stainless steel using PCGTAW process. After welding, the specimens were characterized using optical microscopy and SEM with EDS. The cellular and columnar dendritic structure was obtained from Hastelloy C276-316L stainless steel dissimilar weldments. From the EDS results, it was confirmed that the Mo and Ni content was higher in sub-grain body as compared to the sub-grain boundary in the FZ zone of dissimilar joints. In the case of similar joints of SS 316 L, Mo content was low in sub-grain body, and Ni content was high, vice versa as compared to the sub-grain boundary. As compared to similar welded specimens, the UTS value was high (790 MPa) for Hastelloy C276-316L stainless steel dissimilar specimens prepared using PCGTAW. An improved micro-hardness value of 300 HV was found for Hastelloy C276-316L stainless steel dissimilar welded specimens, compared to similar joints in SS 316 L and HAS C-276. The recorded hardness value for similar (Hastelloy C276 and 316L stainless steel) joints is 230 HV and 245 HV, respectively. Based on the findings of this investigation, it is concluded that PCGTAW process is an appropriate welding technique for making sound welded joints between combinations of the two superior alloys Hastelloy C276 and 316L stainless steel.