Dense silicon carbide mouldings made by sintering without pressure - where aluminium and carbon are mixed with silicon carbide powder before moulding

摘要

The heat resistant mouldings possess a fine crystal structure free from the coarse crystallite-plates 6H-SiC, and are made from a powder mixt. contg. (wt.%) 90-99.6 beta- or alpha-SiC; 0-4 Al added as an addn. (I); and 0.4-6C added as addn. (II). The mixt is compacted by pressing; slipcasting; injection- or other moulding; and the compact is sintered at 1850-2100 degrees C. in an inert or reducing atmos. contg. Al to obtain =85% of the theoretical density of SiC. Addn. (I) is pref. Al, Al-C, AlN, Al-Si-C, or AlB, or an easily pyrolised organic cpd. contg. Al and/or C. Part of the Al may be replaced by max. 0.15%B. The sintering atmos. is pref. Ar,He,Ne,N2 and/or H2, plus a volatile Al cpd. Useful as heat resisting components, e.g. in IC engines or gas turbines.