The Reaction Preparation And Properties Of Sintered Silicon Nitride-based Ceramic Composite Materials

The paper discussed that reaction-sintered Silicon-nitride based composite ceramic was prepared by quasi-static temperature-rising craft with the powder of Si as raw material, SiC and Al as additives. The microstructure, physical properties, mechanical properties and tribological properties have been studied and analysed. The result showed that the strength of Si₃N₄-SiC composite ceramic was improved by adding Al as an important alloy element.The composition of nitrided products, microstructure and morphology of reaction samples were studied by X-ray Diffraction (XRD) and Scan Electron Microscope (SEM). It was observed that α-Si₃N₄ and P-Si₃N₄ were interlaced and lots of pores were filled with fibrous A1N crystal. The volume density of materials was increased and the strength was improved. Result of XRD shows that liquid-phase sintering and formation of β-Si₃N₄ were promoted by adding Al as an important alloy element.The density, pore ratio, bending strength and hardness experiments were carried out. Results show that the density and bending strength of ceramics could be increased significantly at a range of amount of Al addition. Beyond this range, the density and bending strength of ceramics would be decreased. When keeping the portion of Al to Si constant, the density and bending strength of ceramics were increasing with the amount of SiC addition increasing.Results of friction experiment show that the tribological properties of ceramics were influenced by load, lubrication and materials of friction rings. The steady friction coefficient and wear rate would be increasing with load increasing. Water- lubricated condition could be able to decrease the wear rate of materials and improved the wear property of ceramics. The friction coefficient and wear rate of ceramic samples sliding against GCrl5 ring were both lower than samples sliding against Si₃N₄ ring under the same friction condition. It is known from the observation of wear surface the wear mechanism of Si₃N₄ ceramics were adhesive wear, abrasive wear and micro-crack fatigue rupture.