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.