Silicon carbide (SiC) ceramics are known for their exceptional properties, such as high hardness, good wear resistance, low thermal expansion and corrosion stability in harsh environments. SiC comes in both reaction bonded and sintered formats.
Sintering involves reacting and infiltrating vapor phase Si into a porous graphite-based steel billet to produce a full density reaction sintered body, depending on temperature, target temperature hold time and furniture employed during production. Electrical resistivity of this product varies with these variables.
Hardness
Silicon Carbide (SiC) is one of the hardest materials on Earth, able to withstand extreme temperatures, pressures and corrosion without losing its strength. Furthermore, this semi-conductor boasts high thermal conductivity. Due to its hardness and strength, SiC makes an excellent material choice for mechanical seals.
Resistance to wear and corrosion makes these seals especially suitable for use in applications with harsh environments or heavy loads exerted upon them, such as oil and gas production equipment, semiconductor manufacturing plants or general industrial machinery.
Sintered SiC ceramic has the highest strength among ceramics and is known for its exceptional thermal resistance. Even at temperatures as high as 1400degC, its performance remains intact, making it suitable for armor plates, cutting tools and ballistic shields.
Mascera manufactures SiC in two forms: direct sintered and reaction bonded. Direct sintered material uses an a-SiC powder which is heated at high temperatures during sintering to form dense green bodies with strong interconnecting bonds, ideal for high temperature work or as an alternative to reaction bonded materials. Reaction bonded material offers more options and therefore tends to be used more for high temperature work and as replacements in high volume applications.
Reaction-bonded SiC is made from a porous steel billet which is infiltrated with vapor phase silicon to form reactive b-SiC particles that combine with existing a-SiC grains into dense SiC bodies with lower sintering temperatures and improved fracture toughness than direct sintered versions of this material.
Thermal Conductivity
Silicon Carbide features high thermal conductivity and corrosion resistance, making it suitable for high temperature applications. Furthermore, mechanical seals often utilize this material due to its durability and wear resistance properties; up to 1400 degrees Celsius temperatures won’t result in any weakness to its strength.
Thermal conductivity of sintered silicon carbide depends on both its production process and additives, including its sintering conditions and nature of additives. Sintering conditions influence the structure of the ceramic material produced, while different methods result in different microstructures. Reaction bonded and direct sintered forms of silicon carbide exhibit different flexural strengths, thermal expansion coefficients and chemical resistance properties than their direct sintered counterparts.
Sintered sic quality can also be determined by sintering temperature and aids, since density and flexural strength of SiC depend on what type of aid is used; reaction bonded SiC offers good acid and alkali resistance but suffers flexural strength losses after reaching 1000 degrees Celsius.
Direct sintered silicon carbide boasts superior flexural strength, high temperature performance and low coefficient of expansion. Constructed from high-purity a-SiC and additive powder sinterized in a vacuum furnace, its strong bonds produce stronger adhesion than reaction bonded versions and is considered superior grade material.
Resistance to Corrosion
Silicon Carbide is one of the hardest ceramic materials, maintaining its hardness even at high temperatures, making it ideal for high performance pump parts like seals. Furthermore, this material offers very resistant wear resistance as well as good corrosion protection; additionally it weighs half as much as steel making it both lightweight and strong material choice.
Sintered SiC is virtually corrosionproof, showing great resilience against acids (hydrochloric, sulfuric and nitric), bases, solvents and all forms of oxidizing media – such as air. Furthermore, this material’s high mechanical resistance also makes it extremely resilient against mechanical attack from particles or slags.
Flexural strength of polycarbonate is extremely high, and it can withstand temperatures well into the thousands without cracking or shattering. Furthermore, its wide variety of shapes and sizes makes it suitable for many different applications.
Reaction bonded and direct sintered silicon carbide are two primary forms of sintered silicon carbide. Reaction bonding offers lower costs with its coarse grain structure; however, its hardness remains intact even at higher temperatures and offers excellent wear and corrosion resistance. Direct sintered SiC is more costly but boasts much finer grains and an extremely dense structure to withstand both high temperatures as well as mechanical attack.
Corrosion of SiC is complex and highly variable depending on its environment. Studies in industrial furnace environments serve as proof tests, while further research needs to be completed in order to establish long-term corrosion trends and understand how impurities, sintering aids and grain boundary phases influence material behavior.
Strength
Silicon carbide ceramics are among the hardest and most chemically resistant fine ceramics, possessing exceptional heat resistance up to 1400degC without losing strength or showing signs of degradation in strength. Due to this property, silicon carbide finds use in industrial applications requiring sliding contact such as mechanical seals and pump components as well as in semiconductor processing equipment and general industrial machine parts due to its high thermal conductivity and semi-conductivity properties.
Sintered silicon carbide varies greatly in strength depending on its method of manufacturing. Pressureless and hot isostatic pressing sintered ceramics have higher strengths than reaction bonded silicon carbide; these latter ones possessing significant amounts of free silica or other impurities, leading to decreased flexural strength; however they still provide good resistance against acid and alkali solutions, yet may not tolerate extreme temperatures well.
Sintering ceramic powder with boron carbide or carbon enhances its strength, and this process takes place under an inert gas atmosphere to prevent oxidation and promote particle diffusion, leading to higher density and more consistent strength values. Bending strength of Hexoloy SP SiC exceeds reaction bonded or sintered alpha sic and its spherical pores help increase fluid or lubrication reservoir between sliding components for improved performance in various operating conditions.
English 
Swedish