Synergistic effect of V and Ag diffusion favored the temperature-adaptive tribological behavior of VAlN/Ag multi-layer coating

Surface coating technology offers several benefits (excellent wear resistance, low coefficient of friction-COF, better corrosion durability etc.) for key components used in harsh aero-engines. However, the development of temperature-adaptive lubricant coating is still the crucial issue. In this study, VAlN/Ag multi-layer coatings with various thickness ratios were fabricated by a hybrid deposition system composing of DCMS and HiPIMS techniques. Results showed that all coatings presented Ag layers with growth twins, and fcc-VAlN layers with columnar structure. Increasing the temperature from 25 to 650 ℃ led to a decrease of COF from 0.47 to 0.22 in coatings, where the lowest COF and wear rate was particularly achieved at 0.08 and 4.3 × 10−5 mm3N−1m−1 under higher rotation speed, respectively. Based on the microstructural characterizations on wear track of coating and wear scar of counter ball, the synergistic diffusion of V and Ag elements at elevating temperature stimulated the in-situ formation of distinctive Al2O3/AgVO3-Ag3VO4/Ag microstructure, which encompass lubricant phases for lower COF and high wear resistance. The reason behind of this phenomena could be attributed to the easily broken of Ag-O bonds in lamellar silver vanadium oxides at high temperature, accompanying the remarkable lubrication of Ag on top layer. •The VAlN/Ag multilayer coatings were fabricated using DCMS-HiPIMS technology.•Coatings consist of Ag layer with growth twins and VAlN layer with fcc columnar crystal.•A specifically lowest COF of 0.08 obtained at higher rotation speed.•Synergistic diffusion of V/Ag stimulates the Al2O3/AgVO3-Ag3VO4/Ag formed in-situ.•Coating demonstrated excellent temperature-adaptive tribological behavior from 25 to 650 ℃.