The reaction sintered Si3N4 sintered billet was placed in the Si3N4 powder in the presence of sintering aid and resintered at high temperature to obtain dense Si3N4 products. The firing aid may be introduced during ball milling or by immersion after reaction sintering. Because the reaction sintering process can be premachined, the shrinkage in the resintering process is only 6%~ 10%, so the complex shape and excellent performance of the parts can be prepared.
Air pressure sintering is the sintering of Si3N4 billet in nitrogen of 5~12MPa at 1800 ~ 2100'C. Due to the high nitrogen pressure, the decomposition temperature of Si3N4 is improved, which is conducive to the selection of sintering aid which can form high refractoriness intercrystalline phase to improve the high temperature performance of the material. Barsintered silicon nitride ceramics have high toughness, high strength and good wear resistance, and can be directly produced close to the final shape of a variety of complex shape products, which can greatly reduce the cost and
processing expenses. Moreover, its production process is close to that of cemented carbide, which is suitable for mass production.