The Role of Tribofilm Evolution on Tribological Behaviour of Ti₃SiC₂ Ceramic

The Ti₃SiC₂ compound is a thermodynamically stable nano-layered ternary carbide, that belongs to a family of over 50 ternary carbides and nitrides, so-called MAX phases. These phases are a new class of solids that possess a unique combination of properties: they are readily machinable, relatively soft for ceramics, but elastically stiff, and electrically and thermally conductive. However, only very few studies are dedicated to their tribological behavior. This paper presents some results on the tribological behavior of Ti₃SiC₂. During dry sliding on a Ti₃SiC₂ plane, a first regime of low friction and mild wear can be observed, with the build-up of a tribofilm on the counterface. Then, while in an apparently steady state, the tribological behavior suddenly turns to higher friction and severe wear of both counterfaces. Combining friction experiments and topographical observations of contacting surfaces during the first regime, we propose some explanations for such drastic transition in tribological behavior. While tribofilm thickness and roughness stabilize in the mild wear regime, the covering of the ball surface still increases. Thus, matter accumulation on the ball finally leads to seizure of the contact.