同轴送粉激光增材中扫描速度和基板预热对残余应力的影响

Effects of scanning speed and substrate preheating on residual stress in coaxial powder feeding laser additive manufacturing

基于顺序热力耦合方法,以铸态K4169合金为基板,进行高温合金GH4169的单道单层激光增材制造的数值仿真,深入分析了激光扫描速度和基板预热对残余应力的影响。结果表明,降低扫描速度可明显降低沉积层与基板结合处在降温过程中的横向平均温度梯度,而对纵向平均温度梯度几乎没有影响,因此可得降低扫描速度对横向残余应力有比较明显的影响,但对纵向残余应力影响很小。提高基板预热温度可明显降低沉积层与基板结合处在降温过程中的横向和纵向平均温度梯度。考虑到工艺参数的改变本质上是通过温度场变化对残余应力产生影响,构建了峰值温度、平均温度梯度与横、纵向残余应力之间的函数关系。分析显示,横向残余应力对峰值温度的影响更为敏感,而纵向残余应力对平均温度梯度的影响更为敏感。

Based on the sequential thermo-mechanical coupling method,the numerical simulation of single-pass single-layer laser additive manufacturing of superalloy GH4169 with the as-cast K4169 alloy as the substrate was carried out,and the effects of scanning speed and substrate preheating on residual stresses were comprehensively analyzed.The results show that the transverse average temperature gradient during cooling at the junction of the deposition layer and substrate can be significantly reduced by decreasing the scanning speed,but the longitudinal average temperature gradient is almost unaffected.Therefore,it can be concluded that reducing the scanning speed has obvi-ous effect on the transverse residual stress,but has little effect on the longitudinal residual stress.Increasing the preheating temperature of substrate can significantly reduce the transverse and longitudinal average temperature gradient in cooling process of the deposition layer and substrate.Considering the change of process parameters is essentially through the change of temperature field to affect the residual stress,the function relationship between peak temperature,average temperature gradient and transverse and longitudinal residual stress was built.The analysis shows that the influence of transverse residual stress is more sensitive to the peak temperature,and the influence of lon-gitudinal residual stress is more sensitive to the average temperature gradient.