1. Wear resistance

Silicon carbide is second only to diamond in hardness, and has strong wear resistance. It is an ideal material for wear-resistant pipes, impellers, pump chambers, cyclones, and mine hopper linings. Its wear resistance is cast iron. The service life of rubber is 5-20 times, and it is also one of the ideal materials for aviation flight runways. The silicon carbide powder is coated on the inner wall of the turbine impeller or cylinder block by a special process, which can improve its wear resistance and prolong the service life by 1 to 2 times.

2. Corrosion resistance

When the SiO2 contained in the bonding base material of the silicate-bonded silicon carbide material contacts with the substance, it is easy to form a compound with a low melting point, which is easily corroded by the slag, so the chemical resistance of this type of silicon carbide is poor. Since most metal melts cannot wet silicon nitride or silicon oxynitride, they show better erosion resistance than silicate-bonded silicon carbide.

3. Thermal shock resistance

Due to the high thermal conductivity and small thermal expansion coefficient of silicon carbide, this silicon carbide refractory material has good thermal shock resistance. The thermal shock resistance of silicon carbide products is also closely related to the type and properties of the bonding base. The test proves that the sample is quickly put into an electric furnace at 1200 degrees Celsius and heated for 20 minutes, then taken out and cooled in the air to measure the change of elastic modulus. The elastic modulus of silicate-bonded silicon carbide products shows a relatively gentle and gradual downward trend with the increase of the number of thermal shock tests. The silicon nitride combined silicon carbide product is different. Before the 30th cold cycle test, its elastic modulus changes little with the increase of the number of thermal shock tests, and can maintain a fairly constant value. However, after the 31st thermal shock test, the elastic modulus of the sample dropped rapidly, and the sample broke suddenly. Silicon oxynitride-bonded silicon carbide products are similar to silicate-bonded silicon carbide products, and there is no sudden failure. The elastic modulus shows a gentle downward trend with the increase of the number of thermal shock tests. In the actual application process, since the silicate-bonded silicon carbide product can be observed to expand, crack and deform before being damaged by thermal shock, the service life of the material can be easily predicted.

4. High thermal conductivity

Due to the good thermal conductivity of silicon carbide itself, the thermal conductivity of refractory materials with high silicon carbide content is higher, and the thermal conductivity is mostly more than 14.4W/(m.K). The thermal conductivity of the particle surface of silicon carbide products will gradually decrease during use. The properties of the bonding base material have a certain influence on the thermal conductivity of silicon carbide products.

5. Antioxidant

The oxidation resistance of silicon carbide refractory products also varies significantly with the type of bonding base material. The low oxidation resistance of silicon nitride combined silicon carbide products can be explained by their microstructural characteristics. Because the base material of silicon nitride-bonded silicon carbide products is in the form of interwoven fibers, the air permeability is high, and the protective effect on silicon carbide particles is small; in silicate-bonded and silicon oxynitride-bonded silicon carbide products, The surface of the silicon carbide particles is covered by a continuous base material, so it has strong anti-oxidation properties. The oxidation resistance properties of silicate-bonded silicon carbide and silicon oxynitride-bonded silicon carbide show similar behavior in the above tests, but can clearly show differences between them in long-term use.

6. Anti-sticking slag

Slag resistance refers to the ability of silicon carbide bricks to resist the erosion and scouring of slag at high temperatures. The concept of slag here, in a broad sense, refers to metallurgical slag, fuel ash, fly ash, etc. Various materials (including solid and liquid materials, such as sintered cement blocks, calcined lime, iron filings, molten metal, glass liquid, etc.) and gaseous substances (gas, carbon monoxide, fluorine, sulfur, zinc, alkali vapor), etc. The reason why it is difficult to be wetted by slag as a silicon carbide refractory castable is because of the factor of silicon carbide itself. There are various polytypes, of which the 6H polytype is widely used in industry. In 6H-SiC, Si and C are alternately stacked in layers, the distance between Si layers or between C layers is 2.5 Å, and the atomic spacing of Si-C is about 1.9 Å. There is a certain thermal stability relationship between the various types of SiC, and the α and β crystal types are also transformed into each other. When the temperature is below 1600 °C, SiC exists in the form of β-SiC. When the temperature is higher than 1600 °C, β-SiC is slowly transformed into various deformations (4H, 15R, 6H, etc.) of α-SiC through recrystallization. Higher pressures are required for alpha-beta transformations and lower pressures are required for beta-alpha transformations. The transformation between the various types of silicon carbide does not produce volume effects. SiC is a compound with strong covalent bonding. It still maintains high bonding strength at high temperature, so SiC has high hardness, large elastic modulus, excellent wear resistance, and will not be eroded by most acid-base solutions. The intrusion of slag and the low melting point generated by the reaction with the slag have significantly better slag resistance when compared with oxides and the like.