Effect of beam oscillation on the microstructure, residual stress, mechanical and corrosion properties of electron beam welded AISI 304SS joints

The present study concerns the understanding of the effect of beam oscillation on electron beam welded AISI 304 stainless steel. The effect of beam oscillation on the microstructure, mechanical properties and electrochemical properties of electron beam welded AISI 304 stainless steel has been analysed. Welding was carried out using an 80 kV, 12 kW electron beam welding unit, using a static beam and an oscillated beam of varied oscillation diameters (1 and 2 mm). The weld morphology in terms of microstructure and residual stress developed in the weld zone was evaluated. A static beam led to the formation of skeletal dendrites in the fusion zone, while the application of an oscillated beam developed a combination of dendrites of lathy and skeletal morphology. The residual stress developed in the fusion zone and heat-affected zone was meticulously measured and was found to vary with welding parameters. The hardness measurement showed a marginally higher microhardness in the fusion zone when beam oscillation was applied (250 VHN) as compared to static beam (245 VHN). Tensile strength variation shows that an oscillated beam offers a higher yield strength (281–270 MPa) and ultimate tensile strength (785–794 MPa) as compared to the static beam (263 and 751 MPa). The percentage elongation in the weld zone developed with an oscillated beam was 127%, which was 21% higher than that of static beam weld (106%). The electrochemical corrosion behaviour also showed a superior corrosion resistance of the weld zone when beam oscillation was applied. The enhancement of mechanical and electrochemical properties developed by oscillated beams has been stated.