Silicon Carbide – SiC-2

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Silicon carbide sintered without pressure (SSiC) In case of SSiC, densification is achieved through pressureless solid phase sintering at high temperatures between 1900°C (3452°F) and 2300°C (4172°F) in a vacuum or in an argon, nitrogen or similar atmosphere. As the sintering activity of SiC is comparatively low, fine-grained powders having a grain size of normally less than one micrometer are used for densification. In addition, small amounts of free carbon and small amounts of a boron compound (mostly boron carbide) have to be used as additives. SSiC ceramic products have a maximum density of 97%. The high strength of SSiC remains almost unchanged up to about 1600°C (about 2900°F). Corrosion resistance is also very good; however, it varies depending on grain size.

Hot-pressed silicon carbide (HPSiC) / hot isostatically pressed SiC (HIPSiC) This method involves densification through axial (HPSiC) or isostatic (HIPSiC) pressing of SiC powder with simultaneous delivery of thermal energy. The densification rate is higher than with pressureless sintering at the same temperature, resulting in altogether higher densities. With optimised process control, complete densification can be achieved. This leads to even better mechanical properties than for SSiC; durability is also increased once again. The method is, however, limited to relatively simple shapes and also very costly so that HPSiC and HIPSiC are selected only for application under extreme conditions.

Date: 2023-04-10     hits: 532    Return