Superior ablation resistance of plasma sprayed SiC based coating by structural optimized powders

Pristine SiC coating prepared by plasma spraying is difficult to achieve good ablation resistance at high temperature due to its weak SiO₂ scale. Besides incorporation by ultra-high temperature ceramics, the modification of the SiC coating from its feedstock powder is necessary. In the current work, the mixed powders of SiC, Si and C, where the SiC was encapsulated and then carbonized by polydopamine, denoted as SiC@C–Si, were employed as the feedstocks, compared with the mixed case, i.e. SiC–Si–C. The SiC@C–Si coating exhibited superior anti-ablation properties, with a linear ablation rate of 0.62 μm/s, 57 % lower than the SiC–Si–C coating. This is attributed to the fact that nano-carbon formed by carbonization of polydopamine is more prone to reacting with Si than micron-sized C powder, thereby forming a dense microstructure after ablation. Besides, in-situ formed SiC by the depletion reaction increases the flow resistance and decelerates the failure of SiO₂ film, thus improving the ablation resistance.