Effect of SS-316L and nickel-based interface powders on joint characteristics of microwave welded SS-316L plates

Microwave energy has been exploited as a rapid and volumetric heating source in various manufacturing applications, such as microwave joining. This study used stainless steel (SS-316L) plates to be microwave-joined at 2.45 GHz. The microwave hybrid heating (MHH) technique was used to prepare joints inside a microwave applicator using nickel-based (EWAC 1004EN) and SS-316L interfacing powders at 900 W. Microstructural and mechanical characterizations of the developed joints were performed to understand the effect of the interface powder on weld quality. Microstructural observations revealed adequate metallurgical bonding between interfacing powders and bulk metal with columnar and dendritic grains (EWAC-based joint) and equiaxed grains (SS-316L-based joint). The phase analysis revealed the presence of intermetallic phases such as iron-nickel, chromium carbide, and chromium iron carbide in EWAC-based joint and iron-nickel, nickel-chromium, and chromium carbide in SS-316L-based joint, which contribute to enhanced joint microhardness compared to base alloys. A larger grain size, more low-angle boundaries, and higher misorientation angles were found in the EWAC-based joint. Furthermore, the average ultimate tensile strength of SS-316L-based joints was 26% higher, with a 6.9% enhanced elongation, than that of EWAC-based joints. The EWAC-based joint exhibited better corrosion resistance than that of SS-316L-based joint.