Numerical and experimental investigation on microstructure and residual stress of multi-pass hybrid laser-arc welded 316L steel

In multi-layer welding, the interaction between the weld beads had a great impact on the performance of the overall joint. Therefore, experimental research and thermal-plastic analysis of 316L stainless steel multi-layer hybrid laser-arc welding were performed. The reasonable heat sources were proposed to simulate hybrid laser-arc welding (HLAW) and laser beam welding (LBW). The simulation results of temperature field and residual stress distribution were both validated and in accordance with experimental measurements. On this basis, Combining the simulated results with the metallurgical analysis, the microstructure of multi-layer weld was divided according to temperature histories. The formation mechanism of feathery ferrite precipitated in the re-melting zone (RZ) was analyzed. The feathery ferrite could increase the micro-hardness of the interlaminar position of weld. Moreover, the residual stress along the multi-layer weld thickness direction was simulated and X-ray diffraction (XRD) measured, which indirectly demonstrated the size and orientation variation of the grains in the RZ. (c) 2019 The Authors. Published by Elsevier Ltd.