目的 提高42CrMo钢激光淬火后硬化层的深度和分布均匀性。方法 利用COMSOL Multiphysics软件对42CrMo钢激光淬火过程中温度场的演变进行分析，且考虑材料的热物性参数随温度变化。通过设定激光工艺参数模拟试样的温度场分布，利用马氏体转变条件得到硬化层形貌尺寸。参照模拟结果，利用连续输出的光纤耦合半导体激光器对42CrMo钢进行激光淬火实验，用热电偶测温仪对试样测温并与模拟的温度历史曲线进行对比，用光学显微镜对试样横截面处硬化层形貌进行分析，将实验所得硬化层形貌与模拟结果进行比较。并在相同的功率密度下，改变光斑的几何尺寸进行模拟，分析并比较硬化层的几何特征。结果 实验所测某点的温度历史曲线与模拟结果一致性较高，硬化层实际形貌与模拟结果基本吻合。在激光功率密度不变时，随着垂直于扫描方向上的光斑宽度增加，硬化层宽度呈正比例增加，硬化层深度则先增后减，距离硬化层中心最深处相同距离点的曲率则逐渐减少。结论 通过优化激光淬火工艺参数，控制激光淬火的热传导时间和深度方向的温度梯度分布，可以在表面不熔化的前提下，获得较深的硬化层。光斑尺寸对42CrMo钢激光深层淬火硬化层深度和硬化层均匀性有较大影响，选择较大的光斑宽度可以得到更为均匀的硬化层。

The work aims to improve the depth and uniformity of the hardened layer of 42CrMo steel after laser quenching. The temperature field evolution of 42CrMo steel during laser quenching was analyzed by COMSOL Multiphysics software, and the variation of thermal properties of the material along with temperature was considered. The temperature field distribution of the sample was simulated by setting the laser processing parameters, and the morphology size of the hardened layer was obtained under the martensitic transformation conditions. According to the simulation results, the laser quenching experiment was carried out to 42CrMo steel by fiber-coupled diode laser with continuous wave. The temperature of the sample was measured by a thermocouple thermometer and compared with the simulated temperature history curve. The morphology of the hardened layer at the cross section of the sample was analyzed by optical microscopy and the morphology of the hardened layer obtained by the experiment was compared with the simulation results. The laser quenching process was simulated by changing the spot size under the same laser power density and the geometrical characteristics of hardened layer were analyzed and compared. The temperature history curve of a certain point measured by the experiment was consistent with the simulation result, and the morphology of the hardened layer obtained by the experiment was basically consistent with the simulation results. When the laser power density was constant, the width of the hardened layer increased proportionally with increase of the width of the spot perpendicular to the scanning direction, and the depth increased first and then decreased. The curvature of the point with the same distance from the deepest point in the center of the hardened layer gradually reduced. By optimizing the processing parameters of laser quenching and controlling the heat conduction time and temperature gradient distribution in depth direction of laser quenching, a deeper hardened layer can be obtained without surface melting. Spot size has a great influence on the depth and uniformity of laser hardened layer of 42CrMo steel and a larger spot width can be selected to obtain a more evenly distributed hardened layer.