short description:
Silicon carbide (SiC)
Features of the product:
Silicon carbide ceramic is the lightest and hardest ceramic material. It has excellent thermal conductivity, low thermal expansion, very acid and alkali resistance, and is not easy to crack in cold and hot environments.
Therefore, silicon carbide ceramic is an excellent furnace material and high-temperature wear-resistant part. It also has excellent corrosion resistance and wear resistance.
Product performance:
Very low density: (3.20 g/cm ³）
Very high hardness: (94HRA)
High thermal conductivity: (80 W/mK)
Low linear expansion coefficient: (4.5×10-6/K-1400 ℃)
Maximum service temperature: 1500 ℃
Maintain good corrosion resistance and wear resistance at high temperature
The outstanding characteristics of SiC ceramics:
Low density, high elastic modulus; High strength, especially high temperature strength and low temperature; High hardness and low friction coefficient, excellent wear resistance; Low thermal expansion coefficient, high thermal conductivity, and excellent thermal shock resistance; Good chemical stability and excellent corrosion resistance; The resistivity can be controlled by purity and doping, and has semiconductor characteristics.
2. SiC Product series:
As structural ceramics and high-temperature materials with excellent performance, SiC ceramics have been used more and more in petrochemical, iron and steel metallurgy, mechanical and electronic, aerospace, energy and environmental protection, nuclear energy, automobile, high-temperature kiln and other industrial fields.
(1) Sealing ring and bearing:
Due to its excellent wear resistance, high thermal conductivity, high temperature resistance and corrosion resistance, pressureless sintering and reactive sintering dense SiC material is an ideal material for manufacturing sealing rings, sliding bearings and friction protection shaft sleeves. It can be processed into sealing rings with various shapes and high dimensional accuracy and surface finish, which can be used as mechanical seals in many harsh environments. For example, the sealing device and sliding device used for acid-resistant and alkali-resistant pumps in the shipbuilding, chemical, metallurgy, petroleum and paper industries have been widely used due to their good air tightness and long service life.
Take the application of SiC sealing ring in surface sealing of automobile water-cooled pump as an example. The face seal mainly provides the seal of the rotating interface to prevent the liquid or gas on one side of the seal from flowing to the other side. For the water-cooled circulating water pump device of automobile engine, the ceramic ring seal can avoid water leakage during the rotation of the water pump, and can realize sealing and sliding at the same time. In the past, Al and O ceramics were commonly used, but now SiC materials are used because SiC has higher hardness, better wear resistance and longer service life than AlO. Similar SiC sealing rings are also used in automobile air conditioning compressors.
(2) Bulletproof ceramic
Due to its high hardness, low density, good protective performance and low price (compared with B4C ceramics), SiC ceramics have certain competitive advantages in the application of bulletproof armor. Its protective performance is better than that of AL2O3 ceramics and slightly inferior to B4C ceramics (about 70%~80% of B4C ceramics), but the manufacturing cost of SiC ceramics is far lower than that of B4C ceramics. At present, normal-pressure sintered SiC and reaction-sintered SiC ceramic plates are particularly suitable for occasions with large amounts of protective armor and cannot be too thick and heavy. For example, SiC ceramics with high hardness, high toughness and high Weibull modulus (four-point bending strength is 580 MPa, fracture toughness Kc is. 7MPam1/2, Weibull modulus m=17) prepared by American companies are excellent bulletproof materials.
(3) Nozzle
Various nozzles are needed in the fields of petroleum industry, energy, environmental protection, aerospace rocket and machinery manufacturing. SiC ceramics are widely used because of their higher hardness, thermal shock resistance and excellent corrosion resistance than Al2O3 and Si3N4 ceramics. For example, the service life of SiC ceramic is 3.5 times longer than that of Al2O3 ceramic. Reactive sintering, pressureless sintering and recrystallized SiC can be used as burner nozzles in high-temperature kilns and desulfurization nozzles for desulfurization and dust removal in thermal power plants.
(4) Grinding plate Grinding plate is an important process equipment for the production of silicon wafers for ultra-large-scale integrated circuits in the semiconductor industry. Generally used cast iron or carbon steel grinding plates have short service life and large thermal expansion coefficient. In the process of processing silicon wafers, especially in high-speed grinding. During polishing, the flatness and parallelism of the silicon wafer are difficult to be guaranteed due to the wear and thermal deformation of the grinding plate. Because of its high hardness and low wear, and its thermal expansion coefficient is basically the same as that of silicon wafers, the grinding disc made of silicon carbide ceramics can be grinded and polished at high speed. In recent years, the size of silicon wafers has become larger and larger, and higher requirements have been put forward for the quality and efficiency of silicon wafers. The use of SiC ceramic abrasive discs will significantly improve the quality and efficiency of silicon wafer grinding. SiC ceramic abrasive discs manufactured by Kyocera Corporation, Toshiba Ceramics Corporation, and Caballendon Corporation of the United States have been used in the semiconductor industry.
(5) High temperature heat exchanger
In many cases, for example, in metal and glass furnaces, furnaces and coal burning furnaces, the gas emitted is not only high temperature but also corrosive, which requires that the heat exchanger also have high temperature resistance, corrosion resistance and thermal shock resistance, and can withstand large thermal stress. Another performance requirement for heat exchanger materials is high thermal conductivity to maximize heat transfer rate and heat exchanger efficiency. SiC has been the main material of industrial heat exchanger for a long time because of its high thermal conductivity, excellent high-temperature resistance, corrosion resistance and good thermal shock resistance. For example, the SiC heat exchanger of steel forging furnace has been put into use for more than 500000 hours since 1985, and the use of SiC heat exchanger in Hao remelting furnace can save 38% of fuel.
(6) Thermal engine parts
The outstanding high temperature strength, excellent high temperature creep resistance and thermal shock resistance of SiC ceramics make it one of the main materials for thermal engine components in rockets, aircraft, automotive engines and gas turbines. For example, the AGT100 automotive ceramic gas turbine developed by General Motors uses SiC ceramics as high-temperature components such as combustor ring, combustor barrel guide vane and turbine rotor. These SiC components are mainly prepared by reactive sintering, pressureless sintering or hot-pressing sintering. Due to the poor toughness of SiC ceramics, they are mainly used as static heat engine components in engines or gas turbines.
(7) High temperature seal
Both recrystallized SiC and solid-phase normal-pressure sintered SiC ceramics are excellent high-temperature sealing materials, which can be used as high-temperature crossbeam sticks, shed plates, saggers, etc., and the service temperature reaches 1600C, as shown in Figure 8-13 (b) and (h). SAINTGOBAIN, France, uses pressureless sintered SiC ceramics to make the beam of high temperature sealing tool, which has the characteristics of self-bonding and fine grain (<10 um) microstructure, and its high temperature strength and oxidation resistance are very excellent. Under the condition that the bending strength at 1700C is maintained above 400 MPa and 1100C wet steam, the oxidation weight gain is far less than that of recrystallized SiC and SiN-bonded SiC ceramics.
