α-SiAlON–SiC composites obtained by gas-pressure sintering and hot-pressing

摘要: Abstract The objective of this work was the obtaining “in situ” α-SiAlON–SiC composite, using an alternative rare-earth oxide mixture, RE 2 O 3 , as sintering additive, by two different processes. As 20 vol.% AlN–RE in a molar ratio 90:10 mixed to α-Si N 4 powder. In Si –AlN–RE powder 0, 10, 15 and 20 wt.% SiC were added. batches milled, dried compacted cold isostatic pressing. Two processes used: gas-pressure at 1950 °C for 1 h under 1.5 MPa atmosphere, or uniaxial hot-pressing 1750 °C, 30 min pressure 20 MPa. sintered samples characterized X-ray diffraction, scanning electron microscopy mechanical properties. XRD patterns indicate only α-SiAlON (α′) β-SiC crystalline phases. It observed that addition did not influence formation, although growth elongated α′-grains is substantially decreased. hot-pressed composites presented better properties, exhibiting fracture toughness 5 MPa m 1/2 hardness around 21.5 GPa.