Differences between graphite, silicon carbide, and cemented carbide for pump shaft sleeves

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Graphene is the thinnest and strongest nanomaterial known in the world today. Just like single-crystal silicon carbide, it is almost completely transparent. Its thermal conductivity is as high as 5300 W/m·K, which is higher than that of carbon nanotubes and diamond. At room temperature, its electron mobility exceeds 15000 cm2/V·s, also higher than that of carbon nanotubes or silicon crystals. Its resistivity is only about 10-8 Ω·m, lower than that of copper or silver, making it the material with the lowest resistivity in the world; therefore, it is also an excellent semiconductor material. Silicon carbide is produced by high-temperature smelting in a resistance furnace using raw materials such as quartz sand, petroleum coke (or coal coke), and wood chips (salt is added when producing green silicon carbide). Silicon carbide produced in China is divided into two types: black silicon carbide and green silicon carbide. Both are hexagonal crystals with a specific gravity of 3.20–3.25, and a microhardness of 2840–3320 kg/mm2. Among contemporary high-tech refractory materials that are not oxides, such as C, N, and B, silicon carbide is the most widely used and cost-effective one; it can be referred to as emery or refractory sand. Generally, silicon carbide has better self-lubricating properties than cemented carbide, and its cost is lower than that of cemented carbide ； The advantages of cemented carbide include a wider range of applications compared to silicon carbide, as well as greater toughness; it is less likely to break when installing or removing machine seals. The advantages and disadvantages of the two materials complement each other, so it is advisable to consider all factors carefully when making a choice. Additionally, in strong alkaline environments, if silicon carbide is to be used, it is recommended to opt for silicon carbide sintered under normal pressure