Self-lubricating behavior caused by tribo-oxidation of Ti3SiC2/Cu composites in a wide temperature range

Abstract

Ti3SiC2/Cu composite, a new wide temperature range intelligent lubricating functional material, was fulfilled, for mechanical equipment components, by Spark Plasma Sintering process. The microstructure, composition and mechanical properties of the Ti3SiC2/Cu composites (TSC-Cu) were investigated. Additionally, the friction and wear behaviors of TSC-Cu sliding against Inconel 718 were conducted on a pin-on-disk configuration at a sliding speed of 0.5 m/s under a load of 5 N at 25–800 °C. For comparison, the tribological property of polycrystalline Ti3SiC2/Inconel 718 was measured in an identical condition. The worn surface of TSC-Cu was analyzed by SEM, EDS and XPS, respectively. The results indicated that TSC-Cu consisted of Ti3SiC2, TiC and Cu3Si. It was worth noting that the as-formed Cu3Si uniformly distributed along the grain boundary of Ti3SiC2. As for mechanical property, the addition of Cu increased the hardness, compressive strength of TSC-Cu but lowered its flexural strength. Compared with polycrystalline Ti3SiC2, the average friction coefficient of TSC-Cu was higher at 25–400 °C whereas it was lower at 600 °C and 800 °C. The lower friction coefficient was owing to the cooperative lubricating characteristic of tribo-oxidation films containing TiO2, SiO2 and CuO. Furthermore, the wear rate of TSC-Cu was absolutely lower than that of polycrystalline Ti3SiC2, which resulted from the effective surface strengthening effect of the as-formed hard TiC product. Moreover, the wear mechanism of the composite changed from three-body abrasion wear to adhesion wear and tribo-oxidation wear, with the temperature increasing from RT to 800 °C.