Wettability And Tribological Properties Of The Textured DLC Coating Surface

Friction loss not only consumes a lot of resources,but also causes the destruction and replacement of most mechanical parts.If the friction and wear phenomenon can be effectively reduced,it is of great significance to improve energy efficiency and reduce the cost of equipment maintenance and replacement.Based on Reynolds equation,the influence of micro-textures with different size and bottom morphology on hydrodynamic lubrication performance and friction performance is systematically studied by numerical analysis method,and then the optimal micro-textures size and bottom morphology is obtained.Furthermore,Fluent was used to simulate the droplet spreading on the textured surface,and the internal mechanism of micro-textures technology changing the hydrophilic and hydrophobic properties was studied.Finally,micro-textures and DLC coating were fabricated on the surface of YG6 cemented carbide by laser processing technology and plasma enhanced chemical vapor deposition technology.The influence of micro-textures and coating technology on hydrophilic/hydrophobic,tribological properties was studied by wettability test and friction and wear experiment.Based on the theory of hydrodynamic lubrication,square micro-textures(R,V1 and V2)and circular micro-textures(CY and CO)with different sizes and bottom morphologies were established to systematically study the influence of length,diameter,depth,horizontal spacing and longitudinal spacing on the dimensionless average film pressure.The results show that the dimensionless average film pressure of R,V2 and CY first increases and then decreases with the increase of length or diameter,the dimensionless average film pressure of V1 and CO increases with the increase of length or diameter,and the optimal length(diameter)is about 40 μm;the dimensionless average film pressure first increases and then decreases with the increase of depth,and the optimal depth is about 5 μm;in addition,the larger the horizontal spacing and longitudinal spacing,the worse the hydrodynamic lubrication performance.Based on the analysis of the effect of micro-textures on hydrodynamic lubrication,the influence of micro-textures size and bottom morphology on friction performance was studied by numerical method.The results show that The friction coefficient of R,V2 and CY micro-textures first decreases and then increases with the increase of length or diameter,while the friction coefficient of V1 and CO micro-textures decreases with the increase of length or diameter;the friction coefficient of micro-textures first decreases and then increases with the increase of depth;the smaller the spacing between micro-textures,the lower the friction coefficient.Based on the square and circular micro-textures obtained from the previous optimization,the length(diameter)is 40 μm,the depth is 5 μm,the horizontal spacing is 40 μm,and the longitudinal spacing is 40 μm,the influence of micro-textures on wettability was studied by Fluent two-phase flow model.The results show that the droplet contact angle increases by about 10° on the textured surface compared with the smooth surface,and the droplet spreading on the textured surface conforms to the Cassie model.This model explains the phenomenon that the air in the micro-textures space can increase the contact angle.Finally,micro-textures and DLC coating was prepared on YG6 cemented carbide surface by laser processing and Plasma enhanced chemical vapor deposition technology.The influence of micro-textures and coating on wettability and tribological performance was studied by contact angle measurement and friction experiment.The experimental results show that the micro-textures can effectively improve the hydrophobicity of the material surface,which is due to the joint action of the static friction force of the micro-textures surface and the trapped air in the micro-textures(Cassie model);In addition,the combination of micro-textures and DLC coating can effectively reduce the friction coefficient and improve the friction and wear properties of the materials,which is the self-lubrication of DLC coating and the improvement of dynamic pressure lubrication and hydrophobicity of surface.