New processing techniques for the production of pressureless sintered SiC parts

Abstract

For the preparation of SiC parts by casting techniques two different processes for the precipitation of sintering aids onto the surface of sub-micron SiC powder have been developed. In the first case, SiC particles were electrostatically coated with nano scaled carbon. In the second case, SiC has been surface modified to provide coupling groups for the subsequent chemical bonding of carbon. The results show that aqueous slips could be prepared which show no segregation for carbon during slip casting. Green parts ( p > 58%) with a homogeneous distribution of carbon additive have been obtained. As a consequence, samples could be pressureless sintered to high densities (> 98,5%), exhibiting a high fracture strength (>450 MPa) and a high Weibull modulus (>10).