MICROSTRUCTURE, MECHANICAL AND CORROSION PROPERTIES OF AISI 904 L SUPER AUSTENITIC STAINLESS STEEL WELDS BY PULSED GAS METAL ARC WELDING PROCESS

This paper deals with the pulsed gas metal arc welding (P-GMAW) of AISI 904 L super austenitic stainless steel when 1.2 mm diameter of Super austenitic stainless steel filler wire was used. 5 mm thick AISI 904 L super austenitic stainless steel sheets were butt welded by pulsed GMAW process with argon as shielding gas. AISI 904 L Super Austenitic Stainless Steel (SASS) has higher levels of Mo, Cr, Ni, N, and Mn under normal conditions. In heating applications, it offers a superior corrosion resistance at moderate and higher temperatures. The microstructure of SASS is exhaustively austenitic in nature, when subjected to a solution-quenched state. The weld quality depends on bead geometry and its microstructure that influence the mechanical properties of the weld. The coarse grained weld microstructure, higher heat-affected zone, and lower penetration together with higher reinforcement reduce the weld service life in continuous mode gas metal arc welding (GMAW) process. Pulsed GMAW is an alternative method providing a better way for overcoming these afore said problems. It uses a higher peak current to allow one molten droplet per pulse, and a lower background current to maintain the arc stability. Current pulsing refines the grains in weld fusion zone with increasing depth of penetration due to arc oscillations. The main aim of the work is to study the effect of various P-GMAW process parameters and their effects with respect to mechanical properties and metallurgical characteristics of the joints. The microstructural characterization of the joints was performed by optical microscopy. The impact and tensile tests were performed and the fracture surface morphology was analysed through scanning electron microscope (SEM). The hardness test was performed along the longitudinal direction of the weld zone with an equal interval of 2 mm. P-GMAW joints were tested for corrosion resistance using potentio dynamic polarization test. The results showed that the joint by P-GMAW process had higher tensile and impact strength than the base metal. The fractography observation showed the cup and cone shaped fracture, while the weld joint showed a mixed mode of fracture. Therefore, the P-GMAW welding is suitable for welding of AISI 904 L super austenitic stainless steel, owing to their excellent mechanical and corrosion properties.