Microstructure and properties of SiC ceramics fabricated by pressureless sintering at low-temperature

SiC ceramics were fabricated through pressureless sintering at temperature below 1600 ℃ in air by adding Al2O3-Y2O3-CaO sintering additives. Effects of SiC particle size and gradation,binder content,sintering additive content,forming pressure and sintering temperature on microstructure and properties of the SiC ceramics were investigated. The results show that during sintering,the sinteringaiding melt forms and fills into the pores of the sintering bodies. And then,it mainly changes into the crystalline oxides along the SiC particles in the next cooling process. It can effectively promote the sintering densification and improve the microstructure and properties of the SiC ceramics. The SiC ceramics sintered at 1575 ℃ have a density of 2. 93 g / cm3 and a bending strength of 359 MPa,using the 3. 5μm and 0. 5 μm SiC powders at a mass ratio of 3: 1 as raw materials and adding 30 mass% sintering additives.