Nd: YAG Laser Welding of Stainless Steel 304: The effects of Al2O3 micro particles addition 2020-28-0418
In the present work, fabrication of similar Stainless Steel (SS) 304 joints by Nd-YAG Laser Welding Process (LWP). A novel approach was attempted in this study, welding was performed on dual sides of the plate (top and bottom) for a better mixture of micro powder particles in the weld pool region and to achieve maximum depth of penetration, which is not easily possible in a single-sided (LWP). High depth of penetration during fabrication of joints, significantly improved the mixture ratio of molten steel with reinforced micro powder particles. Al2O3 micro powder particles were reinforced in the weld pool region through the drilling process with varying depth ratios, and a moderate gap was maintained between each hole. The effects of Al2O3 on the microstructure and mechanical properties were studied and elaborated in brief. Totally 12 samples were fabricated, here joining was performed by keeping the frequency as constant and varying laser power, travel speed for all the trials. The findings revealed that joints fabricated with powders showed a decrease in the tensile strength and microhardness when compared with joints fabricated without powders. The microstructures for all the samples at the fusion zone showed refined grains irrespective of the joints fabricated with and without powders. However, reduction in mechanical properties is due to discontinuity in the weld pool zone, irregular distribution of powder particles and void defects which are observed in microstructure evolution. A significant increment in tensile strength in transverse cross-section, longitudinal cross-section and, microhardness was observed for the joints fabricated without powders with the operating process parameters as low laser power and travel speed. Low laser power created less heat deposition in the weld pool, low travel speed influenced the contact laser source in the weld region.