Aspects of sintering additives for processing and microstructure development of HIP-SSiC

Additives out of the systems Al-C, Al-B-C and B-C have been investigated wi th respect to densification and microstructure development of SiC produced by pressureless sintering and subsequent post-hot isostatically pressing (H IP) treatment. Within the investigated compositional range, the Al-B-C and B-C systems provide sufficient densification to reach pore closure during p ressureless sintering and nearly theoretical density during the HIP step of the process. Densification in the IU-B-C system takes place at significant ly reduced temperatures, namely similar to 1900 degreesC vs. similar to 205 0 degreesC in the Al- free product. Dilatometer experiments and microstruct ure development indicate the presence of a liquid phase in this system duri ng sintering. Liquid phase sintering in the SiC/(Al-B-C) system vs. solid s tate sintering in the SiC/(B-C) system will be discussed on the basis of li terature data and previous experimental studies of the authors.