超声辅助对激光熔覆Al2O3-ZrO2陶瓷涂层力学性能的影响

目的 探究超声辅助对钛合金表面激光熔覆Al2O3-ZrO2陶瓷涂层力学性能的影响。方法 使用COMSOL Multiphysics仿真软件，探究熔覆工件中有无超声作用下流场的变化，并将超声波直接引入熔池微区，研究超声辅助对Al2O3-ZrO2陶瓷涂层截面形貌、微观组织、元素分布、显微硬度和摩擦磨损性能的影响。结果 仿真结果表明，无超声时熔池横截面涡流大小呈对称状，流速较为缓慢，超声辅助下熔池截面的声速大小瞬时变化，熔池内流体的流速提高。实验结果表明，超声辅助下，熔覆层的截面形貌发生了一些变化，但抑制了熔覆层裂纹的产生。熔覆层晶粒尺寸细化，尤其是当激光功率为1700 W时，晶粒尺寸最小且相对更加致密;熔覆层内元素分布更加均匀，且界面效应降低。熔覆层的力学性能提高，激光功率为1700 W时，熔覆层平均显微硬度值为979.4HV0.2，相同激光功率下，超声辅助的熔覆层具有更大的平均显微硬度值。超声辅助下熔覆层的摩擦系数和波动幅值都较小，激光功率为1700 W时的摩擦系数最小(约为0.329)且波动较为平稳。结论 超声波直接引入熔池微区可以有效提高熔池的流动性，同时细化了晶粒，均匀化了元素分布，提高了熔覆层的力学性能。

Effect of Ultrasonic Assistance on Mechanical Properties of Laser Cladding Al2O3-ZrO2 Ceramic Coating

The work aims to investigate the effect laws of ultrasonic assistance on mechanical properties of laser cladding Al2O3-ZrO2 ceramic coating. COMSOL Multiphysics was used to explore the change of flow field with the ultrasonic assistance. In this method, ultrasonic waves were directly applied on the micro-zone of molten pool. The effect of ultrasonic assistance on the cross-sectional morphology, microstructure, element distribution, microhardness and friction and wear properties were investigated through experiments. The simulation results showed that the size of the eddy current in the cross-section of the molten pool was symmetric and the velocity of flow was slow without the ultrasonic assistance. Under the assistance of ultrasound, the sound velocity of the cross section of the molten pool changed instantaneously and the velocity of fluid in the molten pool increased. Experimental results indicated that the cross section morphology of the cladding layer changed with the ultrasonic assistance, but the cracks in the cladding layer were inhibited. The grain size of cladding layer was refined with the ultrasonic assistance. When the laser power was 1700 W, the grain size was the smallest and relatively denser. The element distribution in the cladding layer was more uniform with the ultrasonic assistance, and the interface effect was reduced. The mechanical properties of the cladding layer were improved with the ultrasonic assistance. When the laser power was 1700 W, the average microhardness value of the cladding layer was 979.4HV0.2. Under the same laser power, the cladding layer had a larger average microhardness value with the ultrasonic assistance. The friction coefficient and fluctuation amplitude of cladding layer were small with the ultrasonic assistance. The friction coefficient was the smallest (about 0.329) when the laser power was 1700 W, and the fluctuation was relatively stable. Ultrasonic wave can be directly introduced into the micro-zone of the molten pool to improve the fluidity of the molten pool, refine the grain, homogenize the element distribution and improve the mechanical properties of the cladding layer.