Reactive silicon infiltration of carbon bonded preforms embedded in powder field modifiers heated by microwaves

Reactive silicon infiltration (RSI) is a process to produce silicon carbide parts by infiltrating microporous preforms bound by pyrolized carbon. Even if RSI is considered one of the fastest manufacturing techniques for the production of SiC parts, long time is required to heat and cool the electric furnaces used for their batch processing. In this paper, we show the benefits of applying microwave power to perform RSI. In this sense a new set up in which preforms are embedded into powder field modifiers is presented. The use of SiC/BN powders as microwave field modifiers revealed the twofold advantage of being an efficient way to heat up the components uniformly while being impermeable to molten silicon. Si-SiC bulk, composite and macroporous ceramics were successfully infiltrated in few minutes. Due to plasma formation, vacuum was not applied. Infiltrations were thus performed at ambient pressure. Finally the different microstructures produced by microwave heating at ambient pressure were compared with standard material produced by conventional heating under vacuum.