Tribological properties of adaptive NiCrAlY–Ag–Mo coatings prepared by atmospheric plasma spraying

Adaptive NiCrAlY–Ag–Mo composite coating was deposited by atmospheric plasma spraying and its tribological properties from 20 °C to 800 °C under unlubricated conditions were evaluated using CSM high temperature tribometer. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy were used to characterize the coating and the corresponding wear tracks to determine the lubrication mechanisms. The results showed that NiCrAlY–Ag–Mo composite coating exhibited low friction coefficients around 0.3 in the entire temperature range and its wear rates were at the order of 10− 5 mm3/N m at all test temperatures. Characterization of NiCrAlY–Ag–Mo coating revealed that silver provided lubrication at temperatures below 400 °C. Silver molybdate and molybdenum oxide, which were formed as the temperature raised, act as lubricants at higher temperature (above 400 °C). Meanwhile, the formation mechanism of silver molybdate and molybdenum oxide was also briefly discussed.