High Temperature Tribological Properties and High-Temperature Lubrication Mechanism of NiAl-Based Composites with the Addition of Ag₂Nb₄O₁₁

The Ag₂Nb₄O₁₁ powders with micro grade particle were synthesized by high-temperature solid state reaction method, then NiAl-based composites with the addition of Ag₂Nb₄O₁₁ (NABO20, NiAl-20%Ag₂Nb₄O₁₁) were prepared by powder metallurgy technology. The influence of silver niobates (Ag₂Nb₄O₁₁) on the microstructure, mechanical properties and tribological behaviors of NiAl-based composites at elevated temperatures was investigated. The results showed that the Ag₂Nb₄O₁₁ phase was decomposed and reacted with C element to form NbC and Ag phase in hot-pressing sintering process. The addition of Ag₂Nb₄O₁₁ slightly increased the density of composite and significantly increased the microhardness of composites. At 800 ℃, because the complete and smooth lubrication films (Nb₂O₅, Al₂O₃, Ag₂Nb₄O₁₁, AgNbO₃ and AgNb₃O₈) on worn surfaces of NABO20 composite and Al₂O₃ counterpart ball prevented the direct contact of the composite and its counterpart, the wear-resistance of the composite was improved effectively.