Britannica Sources used in this answer

How is graphite used as a solid lubricant at high temperatures?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

advanced ceramics Steps in doctor blading, a tape-casting process employed in the production of ceramic films. Ceramic powder and solvent are mixed to form a slurry, which is treated with various additives and binders, homogenized, and then pumped directly to a tape-casting machine. There the slurry is continuously cast onto the surface of a moving carrier film. The edge of a smooth knife, generally called a doctor blade, spreads the slurry onto the carrier film at a specified thickness, thereby generating a flexible tape. Heat lamps gently evaporate the solvent, and the dry tape is peeled away from the carrier film and rolled onto a take-up reel for additional processing.

Graphite functions as a solid lubricant at high temperatures due to its unique layered crystal structure. Within this structure, carbon atoms are arranged in sheets with strong primary bonding within each layer, but weak secondary bonding between the layers.12

Because these sheets can slide over one another with minimal resistance, graphite provides excellent lubricity in environments where conventional hydrocarbon lubricants would break down. This property makes it highly effective for use in sophisticated machinery and engines that operate under extreme temperature conditions.23

It is important to note that graphite’s lubricating performance is dependent on its environment; its low friction is largely attributed to adsorbed films, and in the absence of water vapor, it can lose its lubricating properties and become abrasive. Furthermore, graphite is chemically inert and possesses high thermal stability, which are essential characteristics for its performance as a solid lubricant.4