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The effect of laser shock peening (LSP) on the microhardness and tensile properties of laser cladding (LC) 30CrMnSiNi2A high-strength steel was studied. After LSP, the microhardness of the cladding zone reached approximately 800 HV0.2, which was 25% higher than that of the substrate, while the cladding zone without LSP had an approximately 18% increase in its microhardness. Two strengthening processes were designed: groove LSP + LC + surface LSP versus LC + surface LSP. The former's tensile strength and yield strength were less than 10% weaker than those of forged materials, which is the best mechanical property recovery found in LC samples. The microstructural characteristics of the LC samples were analysed by scanning electron microscopy (SEM) and electron backscatter diffraction. Under the action of the laser-induced shock wave, the grain size of the LC sample surface was refined, the low-angle grain boundaries on the surface layer increased significantly, and the austenite grain length was reduced from 30–40 μm in the deep layer to 4–8 μm in the surface layer. In addition, LSP modulated the residual stress field, hence preventing the weakening effect of the LC process's thermal stress on the components' mechanical properties.

In the present work, a filling and laser shock peening (LSP) method is put forward and applied to a thin-walled pipe. Specimens were experimentally and numerically investigated to identify the residual stress field and fatigue properties of a pipe with and without LSP treatment. The numerical simulation indicated that the residual compressive stress first increased and subsequently dropped as the laser power density increased, and the extent of influence of the stretching wave, reflected from the lower surface on the unloaded area, increased with the spot diameter, causing surface tensile stress in the unloaded area. By filling the pipe with the guided-wave material, the residual stress field of the pipe that was treated with LSP was optimized, and the influence of the stress wave reflection on the residual stress field was effectively decreased. The surface residual stress of the filled guided wave material was −326 MPa, improving it by 57.6% compared with the pipe not filled with guided wave materials. The fatigue life of the pipe with the filled waveguide material that was treated by LSP was extended by 48.9%, compared with the untreated pipe.

No abstract

In present work, a kind of filling laser shock peening (LSP) method is put forward and applied to thin-walled pipe. Specimens are experimentally and numerically investigated to identify the residual stress field and fatigue properties of pipe with and without LSP treatment. Numerical simulation indicates that the residual compressive stress increases first and subsequently drops as the laser power density increased, and the extent of influence of the stretching wave reflected from the lower surface on the unloaded area increases with the spot diameter causing surface tensile stress in the unloaded area. By filling the guided wave material within the pipe, the residual stress field of the pipe treated by LSP is optimized, and the influence of the stress wave reflection on the residual stress field is effectively decreased. The surface residual stress of the filled guided wave material is -326MPa, improving by 57.6% as compared with unfilled guided wave materials pipe. The fatigue life of the pipe with filled waveguide material treated by LSP is extended by 48.9% as compared with untreated pipe.