In-situ formation of layer-like Ag2MoO4 induced by high-temperature oxidation and its effect on the self-lubricating properties of NiCoCrAlYTa/Ag/Mo coatings

Abstract

Ag-Mo-O ternary oxide has attracted growing attention because of its potential as a solid lubricant at high temperatures. This work designs and prepares NiCoCrAlYTa/Ag/Mo composite coating, performed using high velocity oxy-fuel (HVOF) spraying technology. The environment temperature plays an important role in the microstructure and phases as well as lubricant properties of NiCoCrAlYTa/Ag/Mo coatings. When the environment temperature is above 600 °C, the outer diffusion and oxidation of Ag and Mo lead to the formation of Ag2MoO4 on the coating surface. Layer-like Ag2MoO4 could form a continuous lubricant film at 800 °C and consequently let the composite coating present the best tribological properties. Meanwhile, a small number of hard particles could play a good bearing role during friction and improve the tribological properties of the composite coating.