表面织构对模具钢激光熔覆层性能的影响分析

目的 减少激光熔覆过程中产生较大的应力和裂纹的现象,提高激光熔覆后模具钢的抗疲劳性能,延长其使用寿命.方法 选取激光功率(800、1000、1200 W)、扫描速度(5、10、20 mm/s)、光斑半径(0.5、0.75、1 mm)作为激光熔覆模拟因素,以残余应力为主要试验指标,进行三因素三水平正交模拟试验,并对试验结果进行信噪比及极差分析,确定最优熔覆参数.在最优熔覆参数下,进行预置织构及无织构的激光熔覆模拟,对比分析两次模拟的熔覆层温度及残余应力分布.在最优参数下进行熔覆加工,验证有效性.结果 正交模拟试验得出最优熔覆参数为:激光功率800 W,扫描速度20 mm/s,光斑半径1 mm.得到最小残余应力平均值为360 MPa.此外,激光功率对残余应力的影响最为显著,其次是光斑半径,对残余应力影响最小的是扫描速度.在最优熔覆参数下,对预制织构的模型进行激光熔覆模拟,得出残余应力平均值为149 MPa.相比较于无织构熔覆模拟,预置织构熔覆模拟的平均应力值降低了大约58.56％.对无织构和有织构模具钢表面进行激光熔覆加工,测量残余应力,验证了该方法的有效性.结论 通过在基体预置表面织构的方法,在保证熔覆温度的前提下,降低了残余应力,最终能达到降低残余应力、减少裂纹产生的目的.

Analysis of the Influence of Surface Texture on Properties of Laser Cladding Layer on Die Steel

In order to reduce the phenomenon of greater stress and cracks during the progress of laser cladding, improve the fatigue resistance and service life after laser cladding, and extend its service life. Laser power (800, 1000, 1200 W), scanning speed (5, 10, 20 mm/s), spot radius (0.5, 0.75, 1 mm) are selected as simulation factors for laser cladding, and the residual stress is taken as the main experiment indicator during the three-factor and three-level orthogonal simulation experiments. The S/N and range analysis are performed on simulation results to determine the optimal laser cladding parameters. Comparing the cladding temperature and residual stress distribution between prefabricated texture and non-texture cladding simulation under the optimal cladding parameters, and the cladding process is performed under the optimal parameters to verify its validity. The orthogonal simulation experiments show that the optimal cladding parameters of 800 W laser power, 20 mm/s scanning speed, 0.1 mm spot radius, and the minimum residual stress is 360 MPa under the optimal cladding parameters. In addition, the laser power has the most significant influence on residual stress, followed by spot radius, the scanning speed has the least influence on residual stress. The laser cladding simulation of prefabricated texture on die steel results the average residual stress of 149 MPa, which reduces by 58.56% compared with the value of non-texture cladding simulation under the optimal cladding parameters. The effectiveness of the method is verified by measuring the residual stress after the laser cladding processing on the textured and non-textured steel surface. The method of prefabricating surface texture reduces the residual stress under the premise of ensuring the cladding temperature, which verifies the feasibility and superiority of prefabricating surface texture, and finally achieving the purpose of reducing residual stress and cracks.