| Laser metal additive manufacturing technology is an advanced manufacturing technology based on laser cladding technology combined with rapid prototyping technology.Laser additive manufacturing technology can directly produce metal parts with excellent compactness and excellent mechanical properties,and has broad application prospects in aerospace,automotive and weaponry.Laser Additive Manufacturing Material Melting is a process of "rapid cooling and rapid heating",the thermal input produces a non-uniform temperature field that causes the formed parts to have residual stress during subsequent cooling.Residual stress is an internal stress that directly affects the mechanical properties of the part.In severe cases,it will cause crack defects.The laser shock peening technology generates high-temperature and high-pressure plasma on the surface of the part through high-energy laser,and fonns a high-pressure shock wave under the restrained state to produce plastic deformation,thereby generating residual compressive stress and refining crystal grains in the impact region,and improving the mechanical properties of the material.Therefore,this paper proposes a solution based on laser shock enhancement to control the residual stress of laser additive manufacturing.The residual compressive stress generated by laser shock is used to control the residual stress of the laser additive in the part,so as to improve the mechanical properties of the formed part.Based on the finite element technique,the distribution of temperature field and stress field in the cladding layer produced by laser additive was studied.The orthogonal experimental method was used to analyze the influence of process parameters(laser power,scanning speed and spot diameter)of laser additive manufacturing on the residual stress of single cladding layer.It was found that the laser power was 630w,the scanning speed was 6mm/s,and the spot diameter was In the case of 2.2 mm,the residual stress is 261 MPa,which occurs near the surface depth of 0.2 mm from the surface of the cladding layer.The effects of laser shock single pulse energy and different cladding temperature on the residual stress of the cladding layer were studied by ANSYS/LS-DYNA software.It was found that the residual compressive stress of the cladding layer increased with the increase of laser impact energy,and it was found the residual compressive stress generated at the cladding layer of 600 0 C is the largest and the control effect is optimal.In this paper,316L stainless steel is used as the raw material,and the laser additive manufacturing experiment is carried out on the 3161 stainless steel substrate by means of intra-coaxial coaxial powder feeding,the residual stress of the cladding layer along the depth direction(Y direction)of the cladding layer was measured.It was found that the distribution trend of the residual tensile stress of the cladding layer was consistent with the numerical simulation results.The maximum tensile stress was 280 MPa,which also appeared in the cladding layer.Verify the numerical simulation reliability at the top 0.2mm.At the same time,the laser shock strengthening experiments under different pulse energies and different cladding temperatures were carried out on the basis of laser cladding manufacturing.It was found that the average grain size of the cladding layer became smaller after laser impact,and it was treated at 600?.The post-reinforcement effect is the best.The residual tensile stress is changed from 280 MPa to-260 MPa,and the residual stress improvement rate is up to 193%.It provides reference and guidance for the optimization of process parameters for laser shock-enhanced laser additive manufacturing residual stress. |
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