Friction Coefficients of Self-mated Ti₃SiC₂ under Lubrication of Oxide Powders without Supply at Elevated Temperature in Air

The friction coefficients of self-mated Ti₃SiC₂ with and without oxide powder lubricants from ambient temperature to 800 ℃ in air were investigated. The oxide powder lubricants including PbO,ZnO,NiO,TiO₂,B₂O₃,Fe₂O₃,MoO₃,MgO and Al₂O₃ in addition to conventional solid lubricants (graphite and MoS₂ as reference) were used. The results showed that the friction coefficient of self-mated Ti₃SiC₂ tribo-pair could be reduced greatly under lubrication of graphite and MoS₂ powders. Graphite powder was effective in friction reduction below 200 ℃. MoS₂ powder became ineffective above 500 ℃ because of oxidation. Some of the oxide powders were capable of reducing friction coefficient of self-mated Ti₃SiC₂ in narrow temperature range but exhibited higher friction coefficient than graphite and MoS₂ powders. From room temperature to 600 ℃,PbO was the most promising lubricant,while above 700 ℃,TiO₂ and NiO gave moderate friction coefficient. The CM(49lubricating mechanisms of graphite,MoS₂ and oxides powders were discussed in the following aspects,i.e.,film forming properties of the powder,the shear strength and chemical stability of the film.