Investigation into ablation-resistant properties of TiC coating deposited by plasma-spraying for graphite substrate

The comparatively dense Mo bonding layer and TiC ablation-resistant layer was deposited by plasma spraying on graphite substrate. The morphology and the phase structure of coatings, tested with and without oxy-acetylene ablation, were characterized and compared by SEM and XRD. Results indicated that with decreasing the ablation distance, the coating mass ablation rate increased at the initial stage and then decreased, thus finally tended towards stability. As the ablation time increased, the densification region rapidly increased, while the coating mass ablation rate only slightly increased. The ablation process was composed of four stages, namely point-like fusion, linear connection, net connection and perfect densification. Ablated with high temperature fuel flow, the surface TiC layer was transformed to molten TiO₂. Due to the surface tension and viscous flow, a dense TiO₂ layer was finally formed, whereupon reducing the mechanical denudation as well as mass ablation rate.