Femtosecond Laser Processing Of AlN Ceramic Surface For Gradient Wettability Surface Control And It’s Tribological Properties

At present,femtosecond laser processing gradient wettability technology has become an advanced processing technology to control surface wettability.This technology has the advantages of less pollution,good stability and short processing cycle.Therefore,two basic problems are studied in this paper,that is,the influence of laser processing parameters on the micro nano structure of ceramic surface and the influence of micro-dimple structure with different surface morphology on the friction and wear of ceramic surface.The specific research contents and experimental results are as follows:(1)Different laser parameters are selected to process ceramic surface.The influence of different laser processing parameters on the micro texture of the groove surface was studied.Based on the test results,the process parameters were optimized,and the required the groove surface was processed.The experimental results show that as the laser energy density,the number of scanning passes and the overlap rate increase during scanning,the surface becomes hydrophilic and its roughness gradually increases.Through SEM and XPS detection,it is concluded that the surface roughness and the increase in the number of surface chemical C-O bonds have a significant impact on surface wettability.(2)After laser processing,the surface of the micro-dimple structure with different distribution density was obtained.As the distribution density of micro-dimple increases,the contact angles of different micro-dimple show a decreasing trend.As the distribution density of the micro-dimple increases,the contact angle of the surface of the different micro-dimple shows a decreasing trend.According to the contact angle results of the surface of the dimples with different morphologies,according to the order of the wettability,the four types of surfaces are round,square,regular hexagon and regular triangle.Whether it is the groove structure or the micro-dimple structure with different morphologies,the wettability of the structure surface is better,which is more conducive to the directional spreading of the droplets.Therefore,the use of reasonable laser processing parameters to change the topography of the material surface can process wettability surfaces with different gradients,and then achieve the directional movement of the droplets.(3)The friction and wear characteristics of micro pits with different morphologies were studied.The test results show that the friction coefficient of the surface with the micro-dimple structure is smaller than that of the non-micro-dimple structure,and the friction and wear performance of the surface with the micro-dimple structure is significantly improved after laser processing.Under the conditions of dry friction and boundary friction,the surface of the circular dimples has the smallest coefficient of friction and the best wear resistance.Among them,the surface of square micro-dimple was second,and the friction and wear performance of triangular micro-dimple is the worst.