激光熔覆Mo_(2)NiB_(2)熔覆层温度场与应力场仿真研究

Simulation of Temperature Field and Stress Field of Mo_(2)NiB_(2) Coating

激光熔覆工艺参数(激光功率、扫描速度与搭接率等)可对Mo_(2)NiB_(2)熔覆层的温度场与应力场产生重要影响。通过表征激光熔覆工艺参数对熔覆层形貌的影响规律,确定最佳形貌熔覆层的制备工艺;基于有限元模拟间接热力耦合方法,建立平面多道激光熔覆Mo_(2)NiB_(2)熔覆层模型,研究最佳激光熔覆工艺下Mo_(2)NiB_(2)熔覆层的温度场与应力场的变化。结果显示,激光熔覆温度场具有急热急冷、热影响区小的特点,熔覆层温度可达3000 K以上,且随着激光扫描时间的增加,熔覆层的温度逐渐升高;通过应力场云图发现,最大残余应力(506 MPa)分布在熔覆层与基体结合处边缘两侧,并且结合处边缘板厚方向残余应力出现应力集中(应力值315 MPa);纵向残余应力主要受拉应力影响,沿厚度方向逐渐减小,沿X方向先增大后减小的变化趋势,最大纵向残余应力为277 MPa,位于X方向中间位置;熔覆层横向残余应力在Y路径上的分布与纵向残余应力在X方向上的分布大致相同,最大横向残余应力分布在熔覆层Y方向中心位置以及结合处边缘位置,最大值约为259 MPa,并且结合处横向残余应力在Y路径上的分布为拉-压-拉变化趋势,最大压应力仅为92 MPa。

Laser cladding process parameters(laser process rate,scan speed and tying rate,etc.)have an important impact on the temperature and stress fields of Mo_(2)NiB_(2) cladding.Characterizes the influence of laser cladding process parameters on profile of the cladding layer,determines the preparation process of optimal shape cladding layer,establishes a flat multi-channel laser cladded Mo_(2)NiB_(2) cladding model based on the finite element simulation indirect thermal coupling method,and then identifies the changes of the temperature field and stress field of the optimal Mo_(2)NiB_(2)cladding layer.The laser cladding temperature field has the characteristics of rapid heat and the temperature of the cladding can reach 3000 K.With increasing laser scanning time,the temperature of the cladding layer gradually increases.Through the stress field cloud map,the maximum residual stress(506 MPa)was distributed on both sides of the edge of the cladding and substrate binding,while the stress concentration(stress value is 315 MPa)occurs in combination with the residual stress in the direction of the edge plate thickness.The vertical residual stress is mainly affected by pull stress,gradually decreasing along the direction of thickness,increasing first along the X direction and then decreasing.The maximum vertical residual stress is 277 MPa,located in the middle position of X direction.The distribution of the lateral residual stress in the Y path of the cladding layer is nearly the same as that of the vertical residual stress in the X direction,while the maximum lateral residual stress is distributed at the center of the Y direction of the cladding and the edge position at the junction,with a maximum value of about 259 MPa.The distribution of lateral residual stress on the Y path at the junction a the pull-pressure-pull change trend,with the maximum pressure stress to be only 92 MPa.