Tribological properties of self-healing NiCrAlY/Cr3C2-Ti3AlC2 coating at high temperatures

Abstract

Ti3AlC2 is a layered-structure material with both ceramic and metallic properties and is often used as a solid lubricant. To improve the lubrication and wear resistance of engine components in a wide temperature range, especially at high temperatures, a series of Ti3AlC2 enhanced NiCrAlY/Cr3C2 self-lubricating coatings were prepared on TC4 titanium alloy substrates by atmospheric plasma spraying. The tribological properties of the coatings from room temperature to 800 °C were evaluated through a pin-on-disk wear test. The wear mechanism of the coating was analyzed by SEM, XRD and a three-dimensional optical profiler. The results show that the coating with 20 wt% Ti3AlC2 has the lowest friction coefficient (0.341) and lowest wear rate (2.73 × 10−5 mm3 N−1 m−1) among all the samples at 800 °C. The worn surface of the 20 wt% Ti3AlC2 sample was examined after the test. TiO2 particles, together with Al2O3, resulting from the decomposition of Ti3AlC2 in the coating, aggregated on the surface. Compared with the sample without added Ti3AlC2, the high-temperature decomposition products of Ti3AlC2 contributed to the reduction in the friction coefficient and wear rate of the coating. These particles also play a role in filling the worn area on the coating, which endows it with a self-healing ability.