Effects of SiC on phase transformation and microstructure of spark plasma sintered α/β=SiAlON composite ceramics

alpha/beta-SiAlON/SiC composite ceramic tool materials were prepared via spark plasma sintering. The effects of content and size of SiC particles and sintering temperature on phase composition, mechanical properties, and microstructure were investigated. The results indicated that SiC restrained the transformation of beta-SiAlON to alpha-SiAlON, but higher SiC content (>= 10 wt.%) resulted in a higher Vickers hardness of the composite. The large size of SiC particles raised the densification temperature of alpha/beta-SiAlON composites, and small SiC particles benefited to improve microstructure. There were more equiaxed alpha-SiAlON grains and beta-SiAlON with a larger aspect ratio ((alpha) over bar (95) = 5.1) in the alpha/beta-SiAlON composite containing 100 nm SiC. The sample containing 10 wt.% 100 nm SiC particles sintered at 1700 degrees C had the optimal properties with a Vickers hardness and fracture toughness of 18.5 +/- .2 GPa, 6.4 +/- .2 MPa m(1/2), respectively.