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Pressureless Sintering Process and Properties of Silicon Carbide Ceramics
May 21, 2018

As a high-performance special ceramic material with high strength, high hardness, high temperature resistance, corrosion resistance, wear resistance and thermal shock resistance, silicon carbide ceramics are widely used in aerospace, power electronics, machinery industry, petrochemical and many other fields. Since the covalent bond of silicon carbide raw materials accounts for about 80%, it is difficult to sinter dense under normal pressure. In order to sinter silicon carbide ceramics, there are usually many processes including reaction sintering, hot press sintering and other methods which are often used to sinter products, but the properties of the products are often not ideal. In recent years, with the development of sintering theory of silicon carbide products, improvement of fine powder properties, diversification of sintering aids, and in-depth research, the process of sintering high-performance silicon carbide products using a pressureless sintering process has begun to develop. Pressureless sintering process is simple, low cost and the products have excellent performance after sintering, thus become a very popular sintering method.

Through experimental research, it was found that the best molding pressure of silicon carbide ceramics is 140MPa, the best pressure holding time is 90s; the best amount of binder is 3% of the total boring mass; silicon carbide containing C/B4C elements as sintering aids Ceramic sintering belongs to solid-phase sintering. The sintering process is mainly controlled by diffusion mechanism. The best sintering temperature is 2150°C; sintering of silicon carbide ceramics containing Al2O3, K2O, Na2O, MgO and other metal oxides as sintering aids is liquid phase sintering and sintering. The process is mainly controlled by interfacial reaction and the optimum sintering temperature is 1350°C. The maximum density of the silicon carbide ceramics produced by experiments was 3.16 g/cm3 (relative density 98.75%) and the maximum compressive strength was 550 MPa. The results show that the pressureless sintering process of silicon carbide with appropriate content of C+B4C sintering aids is simple and easy to control. After ceramic sintering, compared with the green body, the volume shrinkage of about 30% can be obtained. The higher density and mechanical properties can be obtained. Better silicon carbide specialty ceramics.

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