钛合金表面激光熔覆Ni60A合金涂层熔凝行为的数值模拟与试验验证

Numerical simulation and experimental verification on melting behavior of Ni60A alloy coating on titanium alloy by laser cladding

为了准确预测同轴送粉激光熔覆过程中熔覆层的几何形貌和动态熔凝行为,利用COMSOL MultiphysicsⒸ软件建立了Ti6Al4V合金表面激光熔覆Ni60A合金涂层过程中多相耦合数值模型,并通过单道激光熔覆试验进行了验证。结果表明,模拟结果与试验实际测量的熔覆层截面宽度、高度、深度及稀释率的偏差率分别为-2.63%、12.19%、4.55%和-1.94%,初步验证了模型预测几何形貌的可靠性。另外,为了探究Ni60A合金涂层的熔凝行为,通过模拟进一步获取了熔池内的温度梯度G和凝固速率R的分布图,并结合熔覆层SEM观察表征,建立了晶粒特性与凝固参数之间的关系,发现晶粒类型(平面晶、柱状晶和等轴晶)主要受温度梯度和凝固界面过冷度的影响,而晶粒尺寸主要受凝固速率控制。

In order to accurately predict the geometric morphology and dynamic melting behavior of the clad layer during coaxial powder feeding laser cladding,a multi physical field coupled numerical model for the laser cladding of Ni60A alloy coating on Ti6Al4V alloy surface was proposed by using COMSOL MultiphysicsⒸsoftware and verified by single laser cladding test.The results indicate that the deviation rates between simulation results and experimental measurements in the cross⁃sectional width,height,depth and dilution ratio of the clad layer are-2.63%,12.19%,4.55%and-1.94%,respectively,which preliminarily verifies the reliability of its prediction of geometric morphologies.Besides,in order to investigate the melting behavior of the Ni60A alloy coating,the distribution maps of temperature gradient G and solidification rate R in the molten pool were further obtained by the simulation,and combined with SEM observation and characterization,the relationship between grain characteristics and solidification parameters was established.It is found that the types of grains(planar,columnar and equiaxed)are mainly influenced by temperature gradients and undercooling at the solidification interface,while the grain sizes are mainly controlled by the solidification rate.