In-situ reaction sintering of porous mullite-bonded silicon carbide, its mechanical behavior and high temperature applications

Abstract

The purpose of this work was to study reaction bonding technique as an effective way to produce porous silicon carbide ceramics. These can be tailored to have near-zero dimensional change while sintering, high service temperature under load and excellent thermal shock resistance. Sintered porous mullite-bonded silicon carbide was produced having an open porosity of 20-25%. XRD and SEM were used to confirm formation of the mullite phase and to Study the sample microstructure. Rectangular bars of the material made using the slip-casting method were tested for thermal shock resistance as a function of the critical quench temperature difference the samples could withstand. Cyclic quench tests carried out from 1000 degrees C to 5 degrees C showed a loss in elastic (Young's) modulus of the order of 40% of the initial value in the first 6-8 cycles. Further thermal cycling did not have a significant influence on the elastic modulus. The possibility of the use of porous mullite-bonded silicon carbide in various metal-melting/casting applications has been investigated.