Sliding wear of MAX phase composites Ti3SiC2–TiC and Ti3AlC2–Ti2AlC at 400 °C and the influence of counterface material (steel, Al2O3, and Si3N4) on wear behaviour

This study explores the feasibility of employing MAX phase composite as impregnated solid lubricants and/or as bulk material for advanced high temperature tribological applications. The development of microstructure of Ti-based MAX phase composites Ti3SiC2–TiC and Ti3AlC2–Ti2AlC fabricated by spark plasma sintering and their dry sliding tribological properties against bearing steel, Si3N4, and Al2O3 counterfaces were investigated using a ball on disc tribometer at 400 °C. An orientation relationship between the Ti3SiC2 matrix and TiC particle was established wherein Ti3SiC2/TiC interphase is a coherent boundary from which Ti3SiC2 grows epitaxially from TiC. Against steel, the MAX phase composites – in stark contrast to Si3N4 and Al2O3 – exhibited a negative wear behaviour due to the excessive wear and subsequent sintering of the transferred Fe particles at the sliding interface. Intrinsic lubrication mechanisms involving tribo-oxidation, tribochemical reaction, and mechanochemical reaction played a vital role in the friction and wear properties. The friction and wear properties of the Ti3AlC2–Ti2AlC MAX phase composite was superior to the Ti3SiC2–TiC composite owing to better oxidation kinetics governing the oxide growth and their retention. Evidently, the wear of the MAX phase is expected to proceed upon extensive deformation incorporating a range of microscale micromechanisms.