High-Temperature Heat Treatment of Plasma Sprayed Ti-Si-C-Mo Coatings

In this work, the effect of 800 degrees C and 1100 degrees C post-heat treatment on the plasma spraying of Ti-Si-C-xMo (x = 1.0, 1.5) composite coatings was investigated. The composite coatings were composed of TiC, Ti3SiC2, Ti5Si3 and Mo5Si3 reacted phases. After heat treatment, the Ti3SiC2 and Mo5Si3 phases increased. The coating microhardness decreased by 16% and 18% for Ti-Si-C-1.0Mo and Ti-Si-C-1.5Mo coatings, respectively, after heat treatment at 1100 degrees C. Fracture toughness increased by 16% for the Ti-Si-C-1.5Mo coating after heat treatment at 1100 degrees C, which was mainly due to the heat treatment promoting Ti3SiC2 formation, healing micro-cracks, reducing the internal stress and making the microstructure dense. The coating friction coefficient before and after heat -treatment was between 0.4 and 0.6. After heat treatment, the wear amount of the coating was first reduced and then increased, and the minimum wear loss occurred after heat treatment at 800 degrees C. The wear mechanism was mixed abrasive wear, adhesive wear and tribo-oxidation wear.