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Effects of Laser Shock Peening (LSP) on the Microhardness, Residual Stress and Microstructure in the Weld Joint of a Stainless Steel Tube
G. Xu, J.Z. Lu, C. Y. Cui and K.Y. Luo

Laser shock peening (LSP) is an effective approach to eliminate tensile residual stress, improve microhardness and refine coarse grain in the welding zone, which can significantly improve the mechanical properties of the welded joint. In the present work, microhardness curves and residual stress distributions of the gas tungsten arc welded (GTAW) 316L stainless steel tube before and after LSP were presented and compared. Furthermore, typical microstructure morphologies in the near–surface layer of the welding zone, the heat affected zone (HAZ) and the base metal for both cases were characterized by optical microscope (OM) and transmission electron microscope (TEM) observations. Results indicated that microhardness and residual stress of the GTAW stainless steel tube were significantly improved by laser shock wave. In addition, the relationship between residual stress, microhardness and microstructure in the welding zone of the welded joint were presented.

Keywords: Nd:YAG laser, 316L stainless steel, tube, gas tungsten arc welded (GTAW), laser shock peening (LSP), welded joint, microhardness, residual stress, microstructure, grain refinement

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