The Lubricating Properties of Spark Plasma Sintered (SPS) Ti₃SiC₂ MAX Phase Compound and Composite

Abstract

MAX phase composites Ti₃SiC₂–TiC_x and Ti₃SiC₂–(TiC_x + 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.

Keywords:

• MAX phases
• dry sliding friction
• frictional heating
• tribofilm