Fabrication of SiC matrix composite material by pressureless aluminum melt infiltration in air atmosphere

The microstructure of SiC matrix composite materials produced by pressureless aluminum melt infiltration at 950 was investigated. The oxygen containing phases fraction in silicon carbide preform does not considerably change after soaking in molten aluminum due to the formation of a dense flux film at the surface. It is established that during the direct infiltration of aluminum from the melt into sintered SiC preform, several areas are observed: aluminum saturated zone, transition zone, and a porous silicon carbide zone. The depth of the first area is 1.0-1.2 mm. The open porosity of the infiltrated composite material significantly improved from 8.5% for a SiC preform to 2.4% as well as density increased from 2.17 to 2.85 g/cm(3). Even aluminum content in the zone of porous silicon carbide has grown 5.5 times. The corundum phase has formed at the composite material surface within cooling in the air atmosphere. The hardness distribution over the specimen depth has a parabola-like appearance with a clear maximum on the surface (5.9 +/- 0.6 GPa) and an obvious minimum coinciding in value with the hardness of the initial preform in the geometric center of the sample (2.5 +/- 0.3 GPa). The developed silicon based composite material could be considered as a prospective wear resistant lining.