Oxidation and Heat Shock Resistance of Plasma-Sprayed TiC-CoNi Composite Coatings at 900 °C

Abstract

In this work, the TiC-reinforced CoNi alloy coatings were prepared by the plasma spraying method. Their microstructure, high-temperature oxidation, and thermal shock resistance at 900 °C were studied. The results showed that the CoNi alloy coating exhibited a single phase (c-Co-Ni-Cr-Mo). After adding Ti-graphite mixed powders, the sprayed coating exhibited TiC and TiO2 phases, besides the c-Co-Ni-Cr-Mo matrix phase. For CoNi alloy coating, the main oxidation products were Cr2O3 and CoCr2O4 (NiCr2O4). For TiC-CoNi alloy coating, the main oxidation products were the TiO2 phase, coupled with Cr2O3 and CoCr2O4 (NiCr2O4) phases. The content of oxides increased with the oxidation time. The oxidation weight gain of the TiC-CoNi composite coating was slightly higher than that of the CoNi alloy coating. The formation of TiC could improve the thermal shock resistance of the CoNi alloy coating.