Sintered Silicon Carbide

Silicon carbide is an irreplaceable structural ceramic material due to its exceptional high temperature strength and oxidation resistance, making it indispensable in the fields of mechanical production, aerospace technology and information electronics.

Reaction sintering offers low temperatures and short sintering times while producing near net size shapes, but is limited by uneven density distribution, cracking of sintered products and insufficient silicon penetration during sintering processes.

High Temperature Strength

Silicon carbide is an extremely hard and tough ceramic material renowned for its superior high temperature strength, wear resistance and chemical oxidation resistance properties. Due to these features, silicon carbide finds use in numerous industrial applications including nuclear power plants, furnaces, jet engines, rocket nozzles and papermaking.

One way of improving the high temperature mechanical properties of sintered silicon carbide is through adding additives like aluminium, boron and carbon (SiC-ABC) that enhance creep resistance. These additives alter grain boundary energies and surface energies while increasing volume diffusion rates and discouraging glass formation at grain boundaries.

Another way to increase mechanical properties is with pressureless sintering, which involves the sintering of SiC powder compacts without external pressure being applied. The benefit of this method lies in its elimination of density variations caused by traditional hot pressing sintering methods that result in significant dimensional changes and reduced product quality – it also creates densities closer to theoretical values than ever before.

High Temperature Corrosion Resistance

Silicon carbide exhibits excellent chemical corrosion resistance across a wide range of environments up to 1700 degC, such as dry oxygen, hot gaseous vapors and liquid salts and metals as well as molten salts and coal ash slags.

Sintered silicon carbide offers excellent corrosion resistance due to its structure and surface quality. This material boasts strong resistance against erosion (sliding), mechanical strength, thermal shock and wear.

The high temperature sintered silicon carbide material XICAR (commonly referred to as Hexoloy SE alternative) has proven itself highly resistant to chemical corrosion in acidic environments like concentrated HCl and HNO3, with specimens treated with Y2O3 having higher resistance than those using MgO sintering aid.

Reaction bonded sintered silicon carbide, commonly referred to as self-bonding silicon carbide, is produced by reacting a carbon-containing porous ceramic body with liquid silicon. This mixture infiltrates the ceramic body, reacts with graphite to form b-SiC and then combines with existing a-SiC particles in order to form full density reaction sintered silicon carbide with various shapes available through this process.

High Strength

Silicon carbide is one of the strongest ceramic materials. Boasting superior high temperature strength and oxidation resistance, silicon carbide makes an excellent material choice for use in many industrial applications.

Silicon carbide ceramics can typically be manufactured through either pressureless sintered or reaction bonded manufacturing processes, and Saint-Gobain Performance Ceramics & Refractories offers both types to meet a range of end use applications.

Pressureless sintered silicon carbide is produced by combining fine particle SiC powder with non-oxide sintering aids and sintering it at temperatures greater than 2000degC in an inert atmosphere, producing high density material with superior oxidation resistance, corrosion resistance, and mechanical properties.

Reaction sintering is an emerging process for producing silicon carbide (SiC) ceramics, offering advantages such as dense structures, lower processing temperatures, shape capability, low cost and higher purity. Unfortunately, however, its bending strength falls well short of standard sintered SiC due to residual carbon (Si) sizes in its microstructure.

High Toughness

Sintered silicon carbide ceramics are among the hardest and strongest ceramic materials, while still remaining strong at extremely high temperatures – making it an excellent choice for applications where high temperature resistance is key.

SSIC exhibits nearly constant strength across a wide temperature range and retains its toughness even under intense pressure, making it a highly popular material choice for high-performance pump components and other essential equipment parts.

SSICs are produced using conventional ceramic forming techniques. After being formed into their desired shapes, SSICs are sintered under high temperature and pressure in an inert gas atmosphere.

Sintering can be divided into two distinct phases, solid-phase and liquid-phase sintering. Solid-phase sintering requires the addition of C and B as sintering aids to decrease grain boundary energy of SiC ceramics, while liquid phase uses one or more element eutectic oxides (such as Y2O3) as an agent, creating an electrolytic phase with movement, diffusion and mass transfer between silica particles to densify material density.