Silica gel-coated silicon carbide layer deposited by atmospheric plasma spraying

Atmospheric plasma spraying (APS) of silicon carbide (SiC) is a challenging task due to the severe decomposition behaviour of the SiC. Previous studies, which utilized APS technique, mixed SiC powder with metals and/or metal oxides to prepare SiC coating. None of them sprayed silica gel-coated SiC and examined the characteristics of the coatings. In this work, silica gel-coated SiC, sodium dodecyl sulfate (SDS) enhanced silica gel-coated SiC, and the combination of alumina (Al2O3) and SiC were prepared and then deposited onto a titanium (Ti) plate by APS. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), adhesion and acid resistance test were performed to analyse the characteristics of modified powders and coatings. We found that compared to Commercial-SiC coatings, all the modified SiC coatings not only increase the coating thickness but also enhance the adhesion force between the coating and substrate; furthermore, the SDS-modified sample exhibits good sulfuric acid (H2SO4) resistance. On the other hand, samples containing Al2O3 showed a significant increase in coating thickness and adhesion force, despite a bit lower acid resistance. In sum, we believe that compared to silica-gel coated samples, Al2O3 contained samples are more suitable for industrial application.