Mechanical properties and microstructural characterizations of TIG welded dissimilar joint of A316 stainless steel and AISI 1008 grade steel plates using RSM

Abstract

Welding AISI 316 stainless steel (austenitic) to A1008 carbon steel presents several metallurgical and welding challenges due to the differences in their chemical, thermal, and mechanical properties. This study uniquely investigates the TIG welding of A316 stainless steel to A1008 carbon steel using ER-309 filler with detailed microstructural and mechanical properties analysis. Austenitic A316 stainless steel and AISI 1008 grade steel plates are joined using ER-309 filler wire, and microstructure, tensile strength and impact strength of the dissimilar joints are investigated. The study aims to optimize the process parameters of tungsten inert gas welded dissimilar joints and build model to predict the mechanical properties of the joint. The optimization is carried out using response surface methodology and validated by experimentation. Based on the experimental result, the dissimilar joint has optimum tensile strength of 474 MPa at 160 A, 45 mm/min and 20 l/min as welding current, welding speed and gas flow rate, respectively. Amongst the welding parameters, welding speed and gas flow rate are the dominant factors that significantly impact the weld’s impact strength with 159.95 J. The tensile predicting model has correlation coefficient R² value of 0.9445, while for impact strength, the response model shows R² of 0.8872 suggesting the adequacy and quality of the developed models. The altered distribution of ferrite and austenite phases within the fusion zone promotes finer microstructural features and stronger dislocation barriers, thereby enhancing both tensile and impact performance. Also, the improvement is due to defect free weld with fusion zone characterized with combination of dendritic austenite and inter-dendritic columnar delta-ferrite. This research provides new insights into the welding behavior of rarely studied A316/A1008 combinations and establishes a validated framework for parameter optimization in similar dissimilar metal joints.