Tribological performance and phase transition of MAX-phase/YSZ abradable seal coating produced by air plasma spraying

MAX-phase has excellent high-temperature lubrication performance, which has the potential to be used as the abradable seal coating in aircraft engine combustion chamber. Various concentrations of MAX-phase Ti3AlC2 (2, 5 and 10 wt %) are doped in YSZ-based abradable seal coating as the lubricating phase, and the coating produced by air plasma spraying (APS) on Ni-based alloy. The microstructure and element distribution of the seal coating are studied by field emission scanning electron microscopy (FE-SEM), electron X-ray probe microanalysis (EPMA). The mechanical properties are measured by Vickers hardness test, nanoindentation test and tribological test. The results reveal that with the content of the MAX-phase Ti3AlC2 increasing, the hardness of the abradable seal coating is increased and the resultant wear rate is reduced. The reduction of wear rate is due to the production of some tiny TiC and Al2O3 phases during deposition of Ti3AlC2 in plasma spraying. Comparing with the different MAX-phase content, the wear rate of the composite coating is different. The changes of the nano hardness and wear mechanism of the composite coating after plasma spraying will be discussed.