The lubricating properties of spark plasma sintered (SPS) Ti3SiC2 MAX phase compound and composite

MAX phase composites Ti3SiC2–TiCx and Ti3SiC2–(TiCx + TiC) were synthesized and consolidated via a powder metallurgy spark plasma sintering (SPS) technique. The bulk compositions and microstructural evolution of the resulting SPS discs were analyzed using X-ray diffraction, Raman spectroscopy, and scanning electron microscopy (SEM) paired with an energy-dispersive spectroscopy (EDS) system. The tribological behavior of the synthesized discs was investigated at room temperature under dry sliding conditions using an Al2O3 ball by employing a ball-on-disc tribometer configuration. Postmortem analyses of the worn surfaces showed that the Ti3SiC2 MAX phase exhibited intrinsic self-lubricating behavior due to the evolution of easily sheared graphitic carbon at the sliding surface. The addition of stoichiometric TiC delayed the oxidation kinetics of Ti3SiC2, which favors the evolution of graphitic carbon in lieu of rutile and oxycarbide films. Thus, this work shows comprehensively the existence of an intrinsic self-lubricating behavior of Ti3SiC2 and the important role of secondary-phase TiC in the Ti3SiC2 matrix in its tribological behavior. The wear mechanisms in both composites are dominated by tribo-oxidation triggered by frictional heating. This is then followed by deformation-induced wear upon friction transition.