What Is Silicon Carbide?

Silicon carbide exhibits very high strength at elevated temperatures, as well as great hardness, corrosion resistance, thermal shock resistance, and thermal shock tolerance.

Reaction bonded silicon carbide (RBSiC) is produced by infiltrating liquid silicon into porous carbon or graphite preforms with precise dimensions. This process yields high-density products with precise dimensions.


Silicon carbide, or SiC, is an indestructible ceramic material capable of withstanding high temperatures, chemical corrosion and mechanical wear. As one of the most commonly used abrasive grains with an average Mohs hardness rating of 9 comparable to diamond, SSiC boasts excellent erosion resistance and thermal stability – ideal for applications requiring rapid speed and tolerances during machining operations.

Sintered and reaction bonded silicon carbide are the two primary forms of silicon carbide. Reaction bonded varieties tend to be denser, yet have lower ductility and strength; production involves infiltrating porous metal or ceramic bodies with liquid silicon in order to react with carbon molecules present, fill the pores, then sintering to form dense solid masses.

Sintered silicon carbide (SSiC) is manufactured by pressing and sintering powdered a-SiC with sintering additives into a solid piece of material, usually for applications requiring high levels of strength and hardness. SSiC comes in various shapes and sizes to meet the demands of various industries.

Sintering is a thermochemical reaction in which powder particles combine to form one solid piece of material, creating a single, uniform piece with relatively low temperatures and short times for sintering. This makes SSiC an economical material with superior mechanical properties and chemical resistance than pure CVD a-SiC manufacturing processes.

Corrosion resistance

Silicon carbide exhibits excellent chemical resistance against aggressive environments like hydrochloric and sulfuric acids. Furthermore, its unique structure forms a protective surface layer to provide maximum protection. This explains its high performance against bases (e.g. potash and caustic soda) as well as oxidizing acids like nitric acid. This resistance can be attributed to its inherent properties; which create a passivation layer on its surface.

This layer acts to prevent direct contact between substrate and attacking species and oxygen diffusion through it, significantly decreasing corrosion rates. Its composition and thickness depend on factors like the material used in its construction as well as temperature of exposure or immediate chemical environments in which components exist.

Reaction bonded silicon carbide (RB SiC) outshines conventional sintered silicon carbide (SSiC). Produced by infiltrating liquid silicon into porous carbon or graphite preforms, RB SiC offers superior hardness and strength as well as good thermal shock and corrosion resistance.

Furthermore, RB SiC has demonstrated exceptional compression, tensile, and flexural strengths due to its highly dense microstructure and low processing temperature achieved via reaction sintering. Furthermore, its bending strength increased as residual silicon size decreased; over 1000 MPa has been achieved when controlling silicon particle sizes below 100nm for optimal test results.

Thermal conductivity

Silicon Carbide (SiC) is one of the hardest ceramic materials, boasting excellent wear resistance, temperature stability and thermal conductivity properties. Furthermore, SiC’s corrosion and thermal shock resistance makes it unmatched compared to any other material on the market. Fabricated via reaction bonding or direct sintered methods; reaction bonded SiC offers lower hardness but is cost-effective and easier to work with than its direct sintered counterpart.

SiC thermal conductivity depends heavily on its method of sintering and use of additives. For instance, SiC sintered with 9 weight% Y2O3-Er2O3 exhibits much lower electrical resistivity compared to samples without this additive; this is likely due to large numbers of vacancies and crystallographic defects present within its phase which reduce thermal conductivity.

Sintering additives are added to SiC powder prior to sintering in order to increase density of the finished product and thus enhance density. Unfortunately, however, their addition may increase sintering temperature and decrease flexural strength; as a result it is essential that a balance be found between thermal conductivity and flexural strength of SiC ceramic. This can be accomplished by selecting appropriate sintering additives and adapting the sintering process accordingly; additionally clean grain boundaries help increase thermal conductivity as they help reduce heat loss between grains and voids thus increasing thermal conductivity thereby decreasing heat loss between grains/voids thereby increasing thermal conductivity further; additionally clean grain boundaries also help increase thermal conductivity by decreasing heat loss between grains/voids, ultimately leading to greater thermal conductivity between grains/voids thus increasing thermal conductivity of ceramic.

Chemical resistance

SiC is known for its resistance to corrosion in various chemical environments. This is mainly owing to the formation of an oxide layer on its surface which protects it from direct contact with any potentially corrosive chemicals, while being an inert material with very little chemical reactivity – further adding its resistance.

Pressureless sintered silicon carbide ceramics boast the highest corrosion resistance among non-oxide ceramics, standing up against all common acids (hydrochloric, sulfuric, hydrobromic and hydrofluoric), all bases (amines potash and caustic soda) as well as oxidizing media such as nitric acid. However, its wear resistance falls short of that of cobalt-chromium cemented tungsten carbides while diamond offers greater wear protection.

Reaction Bonded Silicon Carbide may not offer as much corrosion and abrasion resistance, but its high hardness, strength at elevated temperatures and thermal conductivity make it suitable for seal faces, pump parts and other high performance applications. Furthermore, it boasts one of the lowest coefficients of thermal expansion among non-oxide ceramics for optimal performance in various industrial settings.

Junty offers an expansive selection of sintered silicon carbide grades to improve the tribological properties of mechanical seals, cutting tools, wear rings and valve seats. Our experienced staff will work closely with you to select the appropriate grade – either Reaction Bonded or Direct Sintered silicon carbide – for your application.

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