Microstructure and properties of multi-layer and multi-bead parts of 316 stainless steel fabricated by laser-arc hybrid additive manufacturing

In this work, using tungsten inert gas (TIG) arc and laser-tungsten inert gas arc hybrid as heat sources, multi-layer and multi-bead thick wall specimens of 316 stainless steel were fabricated by additive manufacturing technology with different deposit paths. The microstructure, element distribution and mechanical properties of the specimens were studied. The results showed that there were obvious differences in microstructure in the middle area of the specimen. The dendrites of parallel reciprocating specimens were coarse and developed, and the growth direction was highly consistent. And the disordered dendrite growth direction of cross shaped specimen was many, and the interlayer transition area was large. The secondary dendrite of insert stacking was not developed and its microstructure was fine. The Vickers hardness of the specimen decreased first and then increased from the bottom to the top. After adding laser, the arc shrank, the stability and efficiency of the additive manufacturing process increased, and the heat input decreased. Ni and Cr were distributed along the grain boundary at the bottom area of the specimen. The Ni element in the middle and the top area was concentrated in the γ austenite, Cr element was segregated in δ ferrite. In addition, the microstructure of the specimens is finer than that of the specimens with tungsten inert gas (TIG) arc additive manufacturing, and the grain boundaries were mainly small angle grain boundaries. The microhardness and tensile properties of the specimens were improved by adding laser.