Nd: YAG Laser Welding of Stainless Steel 304: The Effects of Al ₂ O ₃ Micro Particles Addition

In the present work, fabrication of similar Stainless Steel (SS) 304 joints by Nd-YAG Laser Welding Process (LWP) was done. 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 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. Totally 12 samples were fabricated and joining was performed 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 low laser power and travel speed. Low laser power created less heat deposition in the weld pool, low travel speed influenced the contact of laser source in the weld region.