Publication

Abstract : Pulsed gas tungsten arc welding (pulsed GTAW) process was used for the autogenous welding of austenitic stainless steel (Type 304L [UNS S30403]) sheets of 3 mm thickness. In the pulse GTAW process, welding current is pulsed between the high peak current and the low background current. The weld was subjected to nonuniform heat input and the cooling rate during each pulse cycle, thereby leading to the segregation of alloying elements and the formation of Cr-depleted zones affecting the pitting corrosion resistance of the weld. Hence, by controlling the pulsed GTAW process parameters, the heat input and variation in the cooling rate of the weldment for each pulse cycle can be controlled, and the pitting corrosion resistance of the weld can be improved. So, a detailed study on the effect of pulsed GTA welding process variables on electrochemical pitting corrosion parameters for the stainless steel weld was carried out and is presented in this paper. Pitting corrosion resistance of the weld was evaluated using the potentiodynamic anodic polarization technique. Mathematical models correlating pulsed GTA welding process variables such as pulse current (Ip), pulse current duration (Tp), and welding speed (S) with pitting corrosion parameters like pitting potential (Epit), corrosion potential (Ecorr), protection potential (Eprot), etc., were developed. Models were checked for adequacy by using analysis of variance (ANOVA). Pitting corrosion parameters predicted by the model were found to confirm the observed value with reasonable accuracy from the conformity test. The developed model will be useful for selecting optimum pulsed GTAW process parameters to control the heat input and cooling rate of the weld, thereby improving pitting corrosion resistance of the weld during welding. Pitting corrosion resistance of the weld was found to be higher when the pulsed GTAW process variables were optimized. A study on the main and interaction effects of pulsed GTAW process parameters on electrochemical pitting corrosion parameters for the weld was presented.