表面技术2025，Vol.54Issue(5)：176-187,12.DOI:10.16490/j.cnki.issn.1001-3660.2025.05.014
同步气体冷却下薄板激光熔覆数值模拟及实验研究
Numerical Simulation and Experimental Study of Thin Plate Laser Cladding under Synchronous Gas Cooling
摘要
Abstract
Laser cladding technology is an advanced surface modification technology for metal materials,which has been widely used in various industrial fields such as automotive industry,aerospace,petrochemical industry,etc.However,in the actual forming process,due to the differences in thermophysical properties between the fusion cladding material and the base material as well as the existence of a high temperature gradient in the heated zone,which leads to plastic deformation due to high local thermal stress,the subsequent cooling contraction phase generates high residual stress,easily leading to deformation of the part.The work aims to reduce the complex residual stress,deformation and coarse grain size generated during laser cladding of thin plates and improve the quality of the cladding layer and the reliability of part assembly. A synchronized gas cooling method for laser cladding with liquid nitrogen for cooling nitrogen was proposed.A three-dimensional numerical model of laser cladding with simultaneous gas cooling was established by a double ellipsoidal heat source,taking into account the temperature-dependent thermophysical parameters,heat conduction,heat radiation,powder-optical interactions,and the role of latent heat of phase transition during solidification.Numerical calculations were carried out for the transient temperature field,the flow field of the molten pool,and the evolution of the stress at different cooling distances.Meanwhile,the actual cross-sectional morphology parameters of the coatings were measured with an ultra-depth-of-field microscope(Keyence VHX-6000),and the results were compared with the numerical simulation data to validate the reliability of the computational model.The amount of substrate deformation after laser cladding was measured with an ultra-depth-of-field microscope.With the three-dimensional imaging capability of the microscope,Conformal measurements of the middle portion of the substrate deformation were performed at a magnification of 100×.Temperature measurements were carried out with thermocouples during the fusion cladding process,the coating microstructure was analyzed with a scanning electron microscope(Zeiss SUPRA55),and hardness measurements were carried out with a microhardness tester(TMHV-1000Z)in the depth direction of the fusion cladding layer at intervals of 0.1 mm(test load of 200 N and maintenance time of 15 s). The introduction of cooling nitrogen enhances the heat exchange between the surface of the molten pool and the external environment,thus improving the temperature distribution of the molten pool and accelerating the cooling rate of the molten pool.Conventional laser cladding and simultaneous gas-cooled laser cladding have basically the same trend in the flow field of the molten pool,presenting a center to surround flow,with a small flow rate at the center and a large flow rate at the edges and the flow rate in front of the molten pool being larger than that at the back of the molten pool.When the cooling distance is 5 mm,the maximum residual stress in the transverse direction of the substrate decreases from 204 MPa to 181 MPa,the residual stress at the top of the fusion cladding layer decreases from 190 MPa to 172 MPa,and the residual stress in the interfacial bonding area decreases from 234 MPa to 211 MPa,and the warping deformation of both sides of the substrate is also reduced by 50%.When the cooling distance is 10 mm,the grain microstructure of the coating is significantly refined,the degree of disordered arrangement of the central columnar crystals increases significantly,and the microhardness of the coating increases from 348.2HV0.2 to 375HV0.2. The method can effectively reduce the residual stress and deformation of the substrate,and provide a new method for better controlling the grain and microstructure of laser melting coating.关键词
激光熔覆/同步气体冷却/残余应力/熔池流场/显微组织/数值模拟Key words
laser cladding/synchronous gas cooling/residual stress/flow field of molten pool/microstructure/numerical simulation分类
矿业与冶金引用本文复制引用
吴志鹏,乌日开西·艾依提,张宇涛..同步气体冷却下薄板激光熔覆数值模拟及实验研究[J].表面技术,2025,54(5):176-187,12.基金项目
新疆维吾尔自治区自然科学基金(2023D01A86) Natural Science Foundation of Xinjiang Uygur Autonomous Region(2023D01A86) （2023D01A86）
