Sintered Silicon Carbide and Its Applications

Silicon carbide has an array of applications in industry due to its excellent properties. These include its resistance against corrosion, oxidation and thermal impact.

React-bonded SiC is produced through the sintering process by infiltrating liquid silicon into porous green bodies of silicon carbide and infusing it under pressure. The final material has low fracture toughness.

High Strength

Silicon Carbide ceramics are known for their extremely hard surfaces that provide excellent abrasion, corrosion and heat resistance properties. Furthermore, this material exhibits excellent oxidation resistance properties along with strong high temperature strength strength levels, chemical stability properties as well as mechanical hardness properties.

Available in various standard sizes and geometries for process equipment applications, silicone seals offer excellent abrasion resistance with reduced friction against mating components in pump seals.

Sintered silicon carbide’s erosion resistant and wear-resistance can be further increased through the application of boron or tungsten carbides, with these special grades offering improved material mechanics at elevated temperatures despite slightly higher raw materials and manufacturing costs.

Reaction bonding or pressureless sintering SiC ceramics produce different microstructures, with the chosen forming methods dictating their end result. Reaction bonded silicon carbide offers lower processing temperatures, excellent shape capabilities and lower costs than pressureless sintered SiC; however its high temperature strength and flexural strength is inferior compared to that produced by pressureless sintered SiC; therefore making reaction bonded silicon carbide better suited for applications that don’t demand the maximum performance from their ceramic material.

High Corrosion Resistance

Silicon carbide ceramics boast one of the highest corrosion resistance ratings of all ceramics and can withstand even severe chemical environments due to its remarkable hardness, strength, thermal conductivity and wear resistance properties. Furthermore, silicon carbide offers excellent oxidation resistance as well as wear resistance properties.

Sintered silicon carbide (SSiC) is produced by pressing and sintering (heating) fine-grained SiC powder with non-oxide sintering aids into a pasty mixture, which can then be compacted or shaped as needed for application or extruded through dies into tubes of sintered silicon carbide.

Reactive sintering involves mixing multiple-element eutectic oxides (such as Y2O3-Al2O3) at low eutectic temperature to form a liquid phase for SiC particle movement, diffusion, mass transfer during densification into sintered ceramic products with precise dimensions; however it has drawbacks like expensive raw materials consumption and energy costs as well as corrosion behavior during densification that must be carefully managed for best performance of SiC ceramics.

High Temperature Resistance

Silicon carbide can withstand high temperatures, making it an excellent material for use in chemical processing equipment such as kilns. Furthermore, its chemical corrosion resistance means it can withstand temperatures up to 1,900deg C while boasting great mechanical hardness properties.

Reaction bonded SiC ceramics are produced using porous carbon feedstock combined with molten silicon, and formed using methods such as dry pressing, casting, and extrusion. They are often employed in composite armor systems used against ballistic threats.

Pressureless sintered Silicon Carbide (PSiC) is an advanced material with exceptional strengths in terms of strength, hardness and thermal conductivity as well as resistance to corrosion, oxidation and bending – ideal for components like nozzles, seals and wear rings.

To increase the sintering efficiency of PSiC, a liquid phase can be created by adding one or more multi-element eutectic oxides such as Y2O3-Al2O3, which have low eutectic points and promote movement, diffusion and rearrangement of SiC particles resulting in densification of product. As a result, SiC ceramics produced have both excellent flexural strength and temperature resistance characteristics.

High Temperature Strength

Sintered silicon carbide boasts high strength that remains relatively constant at high temperatures, making it an excellent material choice for many applications. Furthermore, its chemical corrosion-resistance makes it suitable for many industrial settings.

Reaction bonded silicon carbide (RBSiC), on the other hand, is created through infiltrating molten silicon into porous carbon or graphite preforms and creating porous areas between their structures. RBSiC offers lower strength and hardness than SSiC but offers greater chemical and thermal shock resistance.

Sintering allows for the production of ceramic products with precise dimensions and density, but has its drawbacks: high sintering temperatures can cause densification to shrink during densification; furthermore, this process can produce cracks in material leading to uneven chemical composition or density which could impact performance when exposed to environments that are oxidizing or corrosive. As such, most researchers opt for liquid phase sintering which is also more environmentally friendly.

High Mechanical Hardness

Silicon carbide is one of the hardest materials on Earth and one of the strongest. This combination makes it resistant to corrosion, abrasion and thermal shock while offering good wear resistance and low sliding friction when used against many different mating materials.

Sintered SiC ceramics achieve their high strength through the formation of strong sintering bonds between SiC particles. Pressureless sintering or hot isostatic pressing of silicon carbide produces products with virtually no pores, further improving mechanical properties of ceramic products.

Reaction bonded silicon carbide (RSIC) features more open porosity and coarser grain structure compared to HPSIC or HIPSIC, which reduces its flexural strength and makes it less suitable for high temperature applications.

Direct sintered silicon carbide has finer grains than RSIC and therefore offers greater resistance to oxidation, making it more expensive than its counterpart but providing excellent abrasion, heat, and high-temperature strength properties that make it perfect for pump seals or other demanding high-temperature applications. Direct sintered silicon carbide is commonly specified for pump seal applications that demand superior high temperature strength as well as superior high temperature strength performance.

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