The effects of massive laser shock peening (LSP) treatment on micro-hardness, residual stress and microstructure in four different zones of laser cladding coating was investigated. Furthermore, micro-hardness curves and residual stress distributions with and without massive LSP treatment were presented and compared, and typical microstructure in different zones of both coatings were characterized by transmission electron microscope (TEM)and cross-sectional optical microscope (OM) observations. Results and analyses showed that massive LSP treatment had an important influence on micro-hardness and residual stress of the cladding coating. Special attempt was made to the effects of massive LSP treatment on microstructure in three zones of the cladding coating. In addition, the underlying mechanism of massive LSP treatment on microstructure and mechanical properties of the cladding coating was revealed clearly.
Typical microstructure morphologies in the near-surface layer of the welding zone of gas tungsten arc welded 316L stainless steel tube with and without laser shock peening (LSP) were characterized by optical microscopy and transmission electron microscopy observations. Experimental results and analysis indicated that massive LSP treatment has an important influence on microstructures in the welding zone and heat-affected zone of the welded stainless steel tube. Special attention has been paid to the grain refinement mechanism induced by massive LSP treatment is proposed in the near-surface layer of the welding zone, consisting of the formation of dislocation tangles and dislocation walls due to the pile up of dislocation lines, the development and formation of subgrain boundaries, and the evolution from subgrain boundaries to new grain boundaries. Meanwhile, under laser shock wave, the coarse grain in the near-surface layer in heat-affected zone of the welded specimen was also divided by dislocation movement.
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