Tribological performance of a Ni3Al matrix self-lubricating composite coating tested from 25 to 1000 °C

A Ni3Al–Ag–Mo–BaF2/CaF2 self-lubricating composite coating was fabricated by a powder metallurgical process. The tribological properties of the coating against Si3N4 were investigated over a wide temperature range (25–1000 °C). The results showed that the coating had a low friction coefficient (0.24–0.38) in the entire temperature range. Lubricating mechanism analysis results indicated that Ag took effect at low temperature (below 400 °C); BaF2/CaF2 began to work as a solid lubricant as the temperature raised; and the molybdates, which formed by the fluorides oxidation, act as lubricants at higher temperatures (above 800 °C). As a result, the coating expressed a low friction coefficient from 25 °C to 1000 °C.