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 with respect to densification and microstructure
development of SiC produced by pressureless sintering and subsequent
post-hot isostatically pressing (HIP) treatment. Within the
investigated compositional range, the Al-B-C and B-C systems provide
sufficient densification to reach pore closure during pressureless
sintering and nearly theoretical density during the HIP step of the
process. Densification in the IU-B-C system takes place at
significantly reduced temperatures, namely similar to 1900 degreesC vs.
similar to 2050 degreesC in the Al- free product. Dilatometer
experiments and microstructure development indicate the presence of a
liquid phase in this system during sintering. Liquid phase sintering in
the SiC/(Al-B-C) system vs. solid state sintering in the SiC/(B-C)
system will be discussed on the basis of literature data and previous
experimental studies of the authors.