Construction of dual-layer composite coatings using MAO and CVD to enhance the tribological properties of tantalum-tungsten alloys

To improve the tribological properties of tantalum-tungsten alloys, a dual-layer organic-inorganic functional hybrid coating was fabricated on their surfaces by integrating micro-arc oxidation (MAO) and chemical vapor deposition (CVD). The thickness of the top poly(tetrafluoro-p-xylylene) (PF) layer was adjusted through controlling the deposition duration to investigate its effect on the structure and properties of MAO-PF composite coatings. Our findings revealed that the inherent porous structure within the MAO coating provided numerous anchoring sites for the top PF layer, effectively enhancing the interfacial bonding between the two layers. Both MAO-PF composite coatings with varying thicknesses of PF layers exhibited similar wear behavior, with excellent tribological properties achievable with only thin PF deposition. This enhancement was attributed to the synergistic effects of the supportive and storage functions of the MAO layer, as well as the lubricating properties of the PF layer. Compared with the single MAO coating, friction coefficient was reduced by up to 75% in MAO-PF composite coatings, accompanied by an 85% reduction in the wear rate. Significantly, compared to the uncoated substrate, the composite coatings reduced friction coefficient by up to 80% and wear rate by 98%. Therefore, this novel approach demonstrates promising potential for applications on tantalum-tungsten alloy surfaces.