考察倾斜表面纳秒激光抛光后的表面形貌演化规律及表面倾斜程度对抛光效果的影响规律, 可以为增材制造中的自由曲面激光抛光提供参考。采用纳秒激光对不垂直于光轴的粗糙平面进行激光抛光, 并采用激光共聚焦显微镜对激光抛光后的表面形貌进行测试分析。结果表明: 表面倾斜30°时, 抛光后的表面在距离起始点4 mm附近存在表面轮廓波动异常增大的现象, 表面粗糙度值增大到15.80 μm; 倾斜角度增大到45°时, 表面轮廓波动异常增大的位置变化到2 mm附近; 倾斜角度为60°时, 未发生表面轮廓波动异常增大现象。表面轮廓波动异常增大现象反映了激光抛光从过熔型抛光到浅熔型抛光的过渡过程; 自由曲面的激光抛光工艺需要根据抛光区域的倾斜程度和表面粗糙度选定合适激光功率密度和离焦量, 从而实现良好的激光抛光质量。

The evolution of surface morphology after nanosecond laser polishing of inclined surfaces and the influence of surface inclination on polishing results are investigated, which may provide a reference for laser polishing of free form surfaces in additive manufacturing. A nanosecond laser is used to laser polish rough surfaces that are not perpendicular to the optical axis, and the surface morphology after laser polishing is measured and analyzed using a laser confocal microscope. The results show that when the surface is tilted at 30°, there is an abnormal increase in surface profile fluctuations on the polished surface near 4 mm from the starting point, and the surface roughness value increases to 15.80 μm. When the inclination angle increases to 45°, the position where the surface profile fluctuation abnormally increases changes to around 2 mm. When the inclination angle is 60°, there is no abnormal increase in surface profile fluctuations. The abnormal increase in surface profile fluctuations reflects the transition process of laser polishing from over melt polishing to shallow melt polishing. The laser polishing process for free-form surfaces requires selecting appropriate laser power density and defocus amount based on the inclination and surface roughness of the polishing area, in order to achieve good laser polishing quality.