Tribological properties of NiMo matrix composite containing in-situ formed Sr2NiMoO6 and SrO at elevated temperatures

NiMo alloy and NiMo–5SrSO4 composite were fabricated to reveal the effect mechanism of Sr2NiMoO6 and SrO derived from the decomposition characteristics of SrSO4 in vacuum on the microstructure, density, microhardness, and tribological properties against Al2O3 ball at different temperatures. The formation of Sr2NiMoO6 and SrO led to a negligible increase in the density and microhardness of the sintered composite. Below 400 °C, compared to NiMo alloy, the poor tribological properties were observed in NiMo–5SrSO4 composite, which was responsible for the appearance of Sr2NiMoO6 and SrO on the worn surface. However, with the further increase in the temperature, the friction coefficient and wear rate of NiMo–5SrSO4 composite reached as low around 0.26 and 1.32 × 10−5 mm3/Nm at 800 °C respectively, which was attributed to the synergistic lubricating effect of SrMoO4 generated from the tribochemical reaction between SrO and MoO3, Sr2NiMoO6, and oxides (MoO3, NiO, and NiMoO4) on the rubbing surface.