斜面多道熔覆涂层平整度的数值模拟与试验研究

Numerical Simulations and Experimental Research on Flatness of Inclined Multi-channel Cladding Coatings

目的揭示扫描方式、基材倾角、搭接率对斜面熔池成形的影响规律,提高斜面多道搭接涂层的平整度。方法采用数值模拟探究激光扫描方式、基材倾斜角度、搭接率对倾斜基材表面熔覆涂层平整度的影响机理,并结合正交试验进行验证。结果模拟所得平整度随扫描方式、倾斜角度、搭接率变化规律与试验一致。激光扫描方式对水平基材的多道搭接平整度无明显影响,但对倾斜基材表面的多道平整度影响显著。相同扫描方式下,不同倾斜角度的基材适应的搭接率不同。结论相比其他扫描方式,扫描方式1(SM1)和扫描方式5(SM5)得到的熔覆层平整度和熔覆效率相对较高。平整度和熔覆效率随基材倾斜角度的增大而逐渐减小。以扫描方式5进行熔覆时,水平基材最佳搭接率为30%,基材倾斜40°时最合适的搭接率为15%~20%。显然,倾斜角度和搭接率的交互作用对平整度影响显著。

Some high-strength structural parts have inclined shapes,such as gears,racks,and impellers.Nickel-based coatings are coated on the surface by laser cladding technology,which improves the mechanical surface performance and extends the service life of the parts.Regarding the geometric characteristics of inclined-matrix coatings,existing literature studies the deflection angles of nozzles,inclination angles of substrates,laser scanning methods,and overlapping ratios.Moreover,existing laser scanning methods include up-to-bottom,bottom-to-up,and horizontal continuous scanning for experimental comparative research.Numerical simulations and experimental research were combined.Adjacent or interval scanning was conducted based on the constant working height between the nozzle and the substrate to explore the effects of different laser scanning methods and overlapping ratios on the surface flatness of inclined cladding coatings.In simulations and tests,Ni35A(1×10‒4 m)powders and 45#steel substrates were used to study inclined heat source derivation,model verification,multi-channel fusion process simulation,and experimental design and analysis.The inclined heat source equation was derived according to the planar Gaussian heat source,and heat source parameters were checked through tests and simulations.The consistency of the cladding morphologies was verified to prove the feasibility of the model.Multi-channel morphology research was carried out on the trajectory of single-channel cladding to explore the influences of scanning methods,inclination angles of substrates,and overlapping ratios on the flatness of multi-channel cladding.The laser scanning method significantly affected the flatness of the multi-channel inclined cladding morphology instead of the flatness of planar multi-channel overlapping.When the overlapping ratio was 30%,the cladding flatness obtained by scanning method 1(SM1)and scanning method 5(SM5)was relatively high under the same cladding conditions;that obtained by scanning methods 2,3,4,and 6 was relatively low.The greater the inclination angle of the substrate,the lower the flatness of the multi-channel cladding under the same powder-feeding amounts,laser power,laser scanning methods,and overlapping ratios.Flatness increased first and then decreased as the overlapping ratio increased under the same cladding conditions and laser scanning method.Taguchi orthogonal design was conducted to explore the influences of the inclination angles of substrates,laser scanning methods,and overlapping ratios on the morphologies of multi-channel cladding for inclined cladding substrates.The variance analysis of the test results showed that the flatness of the multi-channel overlapping of the inclined substrate was significantly affected by the inclination angle of the substrate,the laser scanning method,the overlapping ratio,the quadratic term of the scanning method,the quadratic term of the overlapping ratio,the inclination angle of the substrate,and the interaction term of the scanning method.The relationships among the inclination angle of the substrate,scanning method,and overlapping ratio on flatness were consistent with those of the simulation.The inclination angle of the substrate and the scanning method and its square term significantly affected the cladding efficiency,which gradually decreased with the increase of the inclination angle.Compared with other cladding methods,scanning methods 1 and 5 had higher cladding efficiency.Research on scanning methods in the work helps to obtain smoother surface coatings and provides theoretical guidance for applying laser cladding technology in inclined repair or remanufacturing.