A Comparable Study on Laser Welding Behaviors of Selective Laser Melted 304 Stainless Steel, Inconel 718 Superalloy and Ti-6Al-4V Alloy

The hybrid selective laser melting (SLM) technology by laser welding can capture the superiorities of both processes to produce large-scale, high-quality, high-resolution, and complicated-shaped metallic parts. In this work, the SLMed 304 stainless steel, Inconel 718 superalloy, and Ti-6Al-4V alloy sheets were joined by laser welding under various building directions. And then, the microstructure, microhardness, tensile properties, and corrosion resistance of the laser-welded SLMed 304 stainless steel, Inconel 718 superalloy, and Ti-6Al-4V alloy were compared to explore the effect of SLMed microstructural anisotropy and crystal structure. The results showed that phase constitutions were the same between the SLMed and laser-welded joints for the three alloys. But the grain size and dendrite arm spacings in the joints were coarser than those in the SLMed samples. The SLMed microstructural anisotropy resulted in differences in the thermal gradient, grain size, dendrite arm spacing, and tensile properties in the joints under various welding types. Compared with the SLMed counterparts, the laser-welded 304 stainless steel and Inconel 718 joints showed lower microhardness and tensile properties but better corrosion resistance. In contrast, the laser-welded Ti-6Al-4V joints possess a higher microhardness, tensile properties, and corrosion resistance. Therefore, it is feasible to join SLMed parts to manufacture large-scale parts by laser welding.