CORROSION OF SILICON CARBIDE FILTER IN MOLTEN METAL

摘要

Due to its non-wetting behavior, and excellent resistance to corrosion and thermal shock, corrugated silicon carbide filters are suitable for filtering molten metal. This paper illustrated that the corrosion process of silicon carbide by molten copper could be divided into 4 stages; i.e. silica film formation, non-wetting adsorption of molten metal, wetting absorption on glassy surface, and carbon precipitation and bubble formation As soon as the molten metal contacted the silicon carbide surface, oxidation of silicon carbide into silica occurred. The wetting angle of the molten metal gradually became flattened as the glassy phase progressively penetrated into the silicon carbide matrix. If the contact time was prolonged, carbon precipitation was observed. In that case, oxidation of the carbon would give rise to additional carbon-monoxide gas bubbles. The observed corrosion mechanisms could assist designing of the filter materials and morphology for adequate strength and optimum flow rate of molten metal.