Effect of modulation structure on microstructure, mechanical and tribological properties of NiCrMoAl/Al multilayer composite films

Rigid films with multilayer or gradient structures have been widely used in machining applications, where their modulation structure plays a crucial role. In this study, magnetron sputtering was used to prepare thin films with different modulation structures on ZL109 aluminium alloy, and their microstructures, compositional states, mechanical properties and tribological behaviors were systematically analyzed by various characterization methods, and the wear mechanism was deeply understood from the atomic scale with the help of molecular dynamics simulation. The results show that the films exhibit uniform nanoparticle-like, clear multilayer columnar crystal structure with uniform compositional distribution. The modulation structure significantly affects the film properties. When the modulation layer count is 4 layers and the modulation ratio is 8:1, the film hardness and elastic modulus reach their maximum values of 13.67 and 259.4 GPa, respectively. The bond strength is optimal at 17 N, the average coefficient of friction is lowest at 0.28, and wear resistance is most favorable. The primary wear mechanism of the film is abrasive wear. By varying the load for friction and wear tests, it was found that as the load increased, the film friction coefficient showed a tendency to increase first and then stabilize at high loads, and the width and depth of the wear marks gradually increased. The molecular dynamics simulation results show that the higher the indentation depth, the higher the average friction coefficient and the more intense the fluctuation; meanwhile, the increase in the indentation depth leads to an increase in the accumulation of atoms on the surface of the thin film, an intensification of the topography change, an expansion and deepening of the high shear strain region, an increase in the number of wear atoms, and A gradual decrease in dislocation density.