TiC/Ti3AlC2–Co plasma-sprayed coatings with excellent high-temperature tribological properties

In this work, TiC/Ti3AlC2–Co cermet coatings with varying amounts of Ti3AlC2 were deposited by atmospheric plasma spraying (APS) process and their wear-resistant properties were discussed. The friction coefficients and wear rates at high-temperatures were measured through a ball-on-disk type friction test at 600 °C. In addition, the corresponding wear mechanisms were elucidated through the observation of phase changes and surface microstructural evolution of the coatings. The results indicated that the as-prepared coatings consisted of TiC, Ti, TiO2, Al2O3, Co and CoO phases, which were produced by the decomposition and oxidation of TiC and Ti3AlC2. Compared with other samples, the sample with 30 wt% Ti3AlC2 addition displayed the smallest friction coefficient and least wear rate. Its wear rate was about 1.26 times lower than that of reported TiC–Co cermet material and about 10 times lower than that of the typically used TiC–Ni cermet material, suggesting outstanding wear resistance at elevated temperature. The addition of Ti3AlC2 reduced the friction coefficient of the coating by producing more TiC and Al2O3 hard phases and a consequent reduction of coating porosity. When the amount of Ti3AlC2 in the coating was less than 30 wt%, the main wear mechanism was abrasive wear. As the content of Ti3AlC2 was increased in the coating, the wear mechanism changed from abrasive wear to adhesive wear and the wear pattern of the coating gradually transformed from the furrows to the debris. This transformation of mechanism was related to the synergistic effect of hardness and porosity of the coating, which resulted from the remaining content and the special layered structure of Ti3AlC2.