Effect of fluoride content on friction and wear performance of Ni ₃Al matrix high-temperature self-lubricating composites

The self-lubricating composites Ni3Al-BaF2-CaF2-Ag-Cr, which have varying fluoride contents, were fabricated by the powder metallurgy technique. The effect of fluoride content on the mechanical and tribological properties of the composites was investigated. The results showed that an optimal fluoride content and a balance between lubricity and mechanical strength were obtained. The Ni3Al-6.2BaF2-3.8CaF2-12.5Ag-10Cr composite showed the best friction coefficients (0.29-0.38) and wear rates (4.2 9 10-5-2.19 9 10-4 mm3 N-1 m-1) at a wide temperature range (room temperature to 800°C). Fluorides exhibited a good reduced friction performance at 400 and 600°C. However, at 800°C, the formation of BaCrO4 on the worn surface due to the tribo-chemical reaction at high temperatures provided an excellent lubricating property.