为制备低残余应力涂层, 在304不锈钢表面激光熔覆Fe-Mn-Si形状记忆合金涂层。采用ANSYSTM有限元分析软件分析其应力场, 利用机械钻孔法测量相同工艺条件下的激光熔覆试样的残余应力分布特性对模拟结果进行验证, 并采用XRD分析Fe-Mn-Si记忆合金涂层低残余应力机理。结果表明, 激光熔覆产生的应力诱发Fe-Mn-Si记忆合金各涂层γ→ε马氏体转变, 将残余应力释放, 得到低残余应力涂层。在受到各道激光照射(光斑接近至远离)过程中产生的热应力交替呈现为“拉-压-拉”应力状态, 越远离激光热源中心, 热应力越小; 冷却完成后, 激光涂层上残余应力表现为拉应力, 最大应力位于基体与涂层交界处; 在垂直与平行于激光熔覆两个方向上, 涂层中的残余应力均呈现两侧大中间小的分布规律, 在厚度方向上, 熔覆涂层表面至涂层中心残余拉应力逐渐增加到最大值后, 过涂层中心至熔化边界残余拉应力的数值开始逐渐降低, 过涂层边界后, 基体承受压应力并逐渐趋于零应力应力状态。

To prepare a low-residual-stress laser cladding coating, Fe-Mn-Si shape memory alloy(SMA) coating was prepared on the surface of the AISI 304 stainless steel. And the ANSYS finite element software was used to simulate its stress field, meanwhile the residual stress distribution of the cladding specimens was measured by the mechanical hole-drilling method under the same process to verify the correctness of simulation. What′s more, the mechanism of low residual stress inside Fe-Mn-Si SMA coating was analyzed by XRD. The results show that the stress caused by laser cladding induces the γ→ε martensite phase transition inside the coating to get a low residual stress coating. And the coating alternately bears the thermal stress of tensile-pressure-tensile during laser spot getting closer and further to the coating center. And the thermal stress was inversely proportional to the distance between the simulating nodes and the center of laser heat source. When the specimen was completely cooled to the room temperature, the residual stress inside coating presented tensile stress, and its maximum value happened at the junction between the substrate and the coating. In the directions of parallel and vertical to the laser scanning, stress value was relatively small in the middle region, but large in two sides. And from the coating peak to the fusion line in the thickness direction, the residual stress was tensile stress and the extreme value of stress was locating at the center of the coating. Far away from the fusion line, the substrate bore pressure stress and levels off to zero-stress state.