Multiresponse Optimization of Pulsed-Current Gas Tungsten Arc Welding (PCGTAW) for AISI 304 Stainless Steel to St 52 Steel Dissimilar Welds

AISI 304 stainless steel and St 52 steel were dissimilar welded together by pulsed-current gas tungsten arc welding (PCGTAW). The multiresponse Taguchi method was used to optimize the PCGTAW parameters for average microhardness and corrosion potential (E _corr) of weld metal. For three factors (pulse current, background current, and pulse frequency) at two levels, an L4 (2³) orthogonal array was selected. Microstructure and microhardness of weldment were evaluated by light microscopy and Vickers microhardness (HV_0.3). Corrosion resistance of fusion zone in 3.5% NaCl solution was studied using potentiodynamic polarization. The ferritescope was also used to observe the ferrite content on the fusion zone. Multiresponse signal-to-noise ratios and analysis of variance on the measured data were used to identify the optimal levels and relative influence of factors on the variation of the multiple performance characteristics by assigning equal weights to response factors. The results show that the fusion zone microstructure exhibited skeletal delta ferrite in austenite matrix with different ferrite content. Within the selected parameter values, the optimum conditions for microhardness and E _corr were found to correspond to the first level of pulse current (130 A), second level of background current (100 A), and second level of pulse frequency (4 Hz), for constant percentage on-time (50%). The pulse frequency, making a 82.436% contribution, was found to be an effective factor for improvement of microhardness and E _corr of fusion zone, followed in importance by the background current factor with a 16.47% contribution, while the pulse current had less effect compared with the other factors. In this regard, good agreement between the predicted and experimental output factor results is shown.