To enhance the wear resistance and friction-reducing performance of 6061 aluminum alloy, a microarc oxidation/diamondlike carbon (MAO/DLC) composite coating was fabricated via a two-stage MAO process followed by unbalanced magnetron sputtering of a Cr interlayer and a W-doped DLC top layer. The two-stage MAO underlayer (∼46 μm) exhibits a dense inner layer and a porous outer layer, providing robust mechanical support and abundant anchoring sites for the DLC top layer. The deposited W-DLC layer reduces the surface porosity from 13.1% to 2.4% and the surface roughness (Ra) from 2.56 to 0.47 μm. The MAO/DLC composite coating achieves a nanohardness of 1668 HV, significantly higher than the single MAO (1464 HV) and single DLC (1263 HV) coatings, and a critical scratch load (Lc1) of 16.4 N, representing a nearly sixfold enhancement over the single DLC coating (2.8 N). Under dry sliding conditions, the composite coating exhibits an average stable friction coefficient of 0.075, which is 79% lower than that of the single MAO coating (0.35), with a wear track width of only 312 μm after 420 min of sliding. In 3.5 wt. % NaCl solution, the corrosion potential shifts positively from −1080.9 to +148.9 mV, and the corrosion current density is reduced to 1.72 × 10−9 A cm−2, nearly 3 orders of magnitude lower than that of the bare substrate. This synergistic combination of the load-bearing MAO underlayer and the lubricious DLC top layer provides a promising surface modification strategy for aluminum alloys subjected to high-wear and corrosive environments.
Liu et al. (Fri,) studied this question.