Ni ₃Al matrix composite with lubricious tungstate at high temperatures

Ni ₃Al-Ag-BaF ₂/CaF ₂-W composites were fabricated by the powder metallurgy route, and their tri-bological properties over a wide temperature range, starting from room temperature up to 800 °C, were investigated. The Ni3Al matrix composite with 15 wt% BaF ₂/CaF ₂ exhibited a favorable friction coefficient (range 0.3-0.4) and wear rate (0.2-6.2 × 10 ^-4mm ³ N ^-1 m ^-1). The formation of BaWO4 and CaWO4 with lubricity on the worn surface due to a tribo-chemical reaction at high temperatures provided excellent lubricating properties. The low friction coefficient over a broad temperature range could be attributed to the synergistic effect of Ag, BaF ₂/CaF ₂, BaWO ₄, and CaWO ₄.