激光宏观抛光对激光沉积层表面形貌及力学性能影响

Influence of Laser Macro Polishing on Surface Morphology and Mechanical Properties of Laser Deposition Layer

针对金属激光3D打印、激光熔覆等激光沉积成形工艺表面质量差、难以直接装机使用的工艺难题,利用光纤半导体耦合激光器对铁基激光熔覆层进行宏观抛光处理,研究激光抛光对激光沉积成形表面形貌和物理力学性能的影响规律。首先采用手持显微镜和白光干涉仪对熔覆层激光抛光宏观形貌和粗糙度进行测试、分析与表征,然后使用扫描电子显微镜(SEM)对熔覆层微观组织进行测试分析,进而利用显微硬度计测试熔覆层沿深度方向的微硬度值,利用X射线应力测试仪对熔覆层表面残余应力测试。研究结果表明,激光抛光熔覆层宏观形貌平整,激光熔覆层的粗糙度显著降低;比较了不同抛光次数对表面质量的影响,抛光一次后熔覆层中部微观组织为平面胞状晶,抛光两次熔覆层中部微观组织为细小的等轴晶;抛光一次后表面残余应力为压应力,抛光两次后表面残余应力为拉应力;抛光两次后的显微硬度较原始熔覆层提高1.3倍,较基体提高3.5倍。

Aiming at the process problems of poor surface quality of metal laser 3 D printing, laser cladding and other laser deposition forming processes, it is difficult to directly install the machine, using a fiber-semiconductor coupled laser to polish the iron-based laser cladding layer. The influence of laser polishing on the surface morphology and physical and mechanical properties of laser deposition forming was studied. Firstly, the macroscopic morphology and roughness of the laser polishing cladding were tested, analyzed and characterized by hand-held microscope and white-light interferometer. Then, the microstructure of the cladding layer was tested and analyzed by scanning electron microscope(SEM). The microhardness value of the cladding layer along the depth direction was tested by X-ray stress tester. The results show that laser polishing cladding macroscopic morphology is smooth and the roughness of the laser cladding layer is significantly reduced. The effects of different polishing times on the surface quality is compared. After the first polishing, the microstructure of the middle of the cladding layer is planar cell crystal, and the microstructure of the middle of the cladding layer is the fine equiaxed crystal after two times polishing. The surface residual stress of the cladding layer is compressive stress after the first polishing, the surface residual stress of the cladding layer is tensile stress after the two times polishing. After two times of polishing, the microhardness is 1.3 times higher than the original cladding and 3.5 times higher than that of the substrate.