Friction and Wear of Ti₃SiC₂-derived Carbon Coatings in Vacuum

Carbide derived carbon coating on Ti₃SiC₂ substrate (CDC@Ti₃SiC₂) was prepared by chlorination at 800 ℃ in a flow of 5% Cl₂ + Ar gas mixtures. By using the porous and lamellar structure of the CDC@Ti₃SiC₂ coating as a reservoir for ionic liquids (e.g. 1-hexyl-3-methylimidazolium hexafluorophosphate, LP106), a solid-liquid duplex lubricating coating(CDC@Ti₃SiC₂-LP106 coating) was obtained by vacuum impregnation.The tribological properties of bare Ti₃SiC₂, CDC@Ti₃SiC₂ coating and CDC@Ti₃SiC₂-LP106 coating sliding against a Si₃N₄ ball were investigated in two modes, i.e. high vacuum (10^-4 Pa) and progressive evacuation from 10⁵ to 10^-4 Pa. The friction coefficient of CDC@Ti₃SiC₂ coating firstly decreased with the decreasing background pressure and then increased in high vacuum. In comparison, the friction coefficient of CDC@Ti₃SiC₂-LP106 coating was low and insensitive to the variation of the background pressure. In both modes, CDC@Ti₃SiC₂ coating and CDC@Ti₃SiC₂-LP106 coating significantly reduced the friction coefficient of bare Ti₃SiC₂ without obvious improvement on the wear resistance.