Microstructual and mechanical studies of the dissimilar tabular joints of Incoloy alloy 825 and AISI 316 stainless steel

In this work, dissimilar welding of Incoloy alloy 825 and AISI 316 stainless steel tubes is experimentally investigated using gas metal arc welding process. For this purpose, different filler metals such as stainless steel 308, stainless steel 309, stainless steel 316 and Inconel 82 are employed for joining of Incoloy alloy 825 and AISI 316 stainless steel tubes. The results show that during tensile tests, fracture occurred in all weldments in the heat-affected zone (HAZ) of stainless steel 316. Also, it is concluded that dissimilar welds produced by stainless steel 309 filler metal have the maximum tensile strength while the lowest strength is obtained with Inconel 82 filler metal. The results of average hardness prove that the dissimilar joint with filler metal say stainless steel 309 and filler metal say Inconel 82 have maximum and minimum values of average hardness in the weld metal, respectively. The results show a considerable unmixed zone (UMZ) in the form of laminar layers between filler 82 weld metal and the Incoloy 825 base metal along the welding line. In addition, considerable UMZ is seen in the interface of the weld metal/AISI 316 base metal, but more grain growth occurred in the AISI 316 HAZ due to the temperature increase during various welding passes. It is indicated that there is a very narrow UMZ between the 309 weld metal and Incoloy 825 base metal; however, no considerable UMZs can be observed in the AISI 316 base metal.