The paper presents a novel low activation brazing technique for SiCf/SiC composites. The brazing alloy does not contain free silicon and is based on the use of a Si-44Cr at.% eutectic and the intermetallic CrSi2(melting temperatures 1390 and 1490°C, respectively). These are advantageous because the melting point is low enough to avoid degradation of the advanced fibres and of the interphases in the composite, and the Si-Cr intermetallics are chemically compatible with silicon carbide. Both the eutectic and the intermetallic were prepared before brazing operations by melting a Si-Cr mixture. The joining was performed under vacuum (about 10-4Pa). Systematic investigations of the microstructure and of the nanochemistry (TEM, EELS, ELNES) of the Si-Cr joints reveal that direct chemical Si-Si, Cr-C and Si-Cr bonds across the interface are responsible for the adhesion: the interfaces were proved to be nearly atomically sharp and adhesive. Altogether, this brazing procedure enables joints with sufficient strength and with a microstructure comparable with that of the starting powders to be obtained. © 2004 Elsevier B.V. All rights reserved.
All Science Journal Classification (ASJC) codes
- Nuclear and High Energy Physics
- Materials Science(all)
- Nuclear Energy and Engineering