Preparation and property of immersion heater with SiC composite ceramic sheath

The SiC composite ceramic sheath with multi-layer structure was fabricated via reaction sintering and pressureless sintering processes using SiC powder as a raw material. The inner sheath was a dense SiC/Si composite material, and the outer sheath was a SiC/C/SiC composite ceramic. The immersed experiment was carried out from SiC composite sheath into molten aluminum at 750°C for 360 h. The density and bending strength of the composites before and after immersed experiment were examined, and the microstructure and phase composition of the composites were investigated. The results show that the SiC sheath has a good thermal shock resistance and a molten erosion resistance in the immersed experiment. The inner materials had a good oxidation resistance due to its high density. The bending strength of the outer part of the composite immersed in the melt was decreased by <10%, and the residual bending strength of upper melt part reached 48 MPa. Therefore, the SiC composite ceramic sheath exhibited a promising application prospect in the molten non-ferrous metals.