Mechanical and tribological performances study of PEEK/CNT reinforced EP coatings via molecular dynamics simulation

The research for coating materials with low coefficient of friction, low wear rate, and high strength is important for industrial lubrication and protection. This study provides an approach of double-layer coating as protective coating, with carbon nanotube (CNT) and polyether ether ketone (PEEK) as reinforcing nano-fillers. The mechanical and frictional properties of four types of single layers were investigated for the selection of top layer. The selection of bottom layer was based on the adhesion between the coat and the substrate. According to the analysis results, the molecular models of CNT and PEEK reinforced EP layer and pure EP layer were applied as top and bottom layers of a coating, respectively, named as EP-PEEK/CNT/EP coating. For comparison, a pure EP double-layer coating (named as the EP-EP coating) was developed. The friction and wear of these two coatings against a Cu counter friction partner were observed from the atomic scale using molecular dynamics (MD) simulation. The coefficients of friction were analyzed by extracting the relative atomic concentrations and relative atomic velocities of the coatings along the Z-direction during shear, while the friction losses were analyzed using the values of mean-square displacement (MSD) function and radial distribution function (RDF). The simulation results showed that the stronger interaction force between PEEK/CNT and EP molecules led to a lower coefficient of friction and reduced friction loss for the EP matrix of the coating. Additionally, the use of pure epoxy resin as the bottom layer ensured stronger adhesion to the substrate.