Evaluation of the Melted Zone Microstructure in the Interface of the Dissimilar Weld between A335 Low Alloy Steel and ER309L Filler Metal by Gas Tungsten Arc Welding

In the present study, the microstructure and mechanical properties of the dissimilar welding between ASTM A335 low alloy steel and ER309L austenitic stainless steel were investigated using the gas tungsten arc welding process. The welding of dissimilar materials between ASTM A335 low alloy steel and ER309L austenitic stainless steel was found to have a significant effect on the microstructure when the filler metal of ER309L was used. This research also studied the effect of carbon migration from the heat-affected zone (HAZ) to the melted zone in the interface between A335 low alloy steel and 309L filler metal using microstructure analysis and Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) Line Scan Technique. The results showed that the solidification of 309L as a primary ferrite exhibited a skeletal ferrite morphology and the solidification of ferritic-austenitic (FA) type. Moreover, the results of EDS provided evidence showing carbon migration from the low chromium side to the weld metal which had a higher chromium content and a tiny martensitic zone occurred in the melt boundary with a high hardness value. In the tensile test, all specimens were broken in the HAZ of A335 low alloy base metal with a ductile fracture and the welded specimens also showed the ductile fracture in the impact test.