Carbon and graphite are two very different things, although it is common for people to use the two terms as if they were the same.
The Two Forms
Carbon, specifically amorphous carbon, is very strong and it is hard to the touch. Amorphous carbon stands up to wear, and it can be an ideal choice where it is essential for a component to be able to be highly resistant to contact.
Graphite is the opposite and is soft and weak. It is made up of layers and not the dense crystals of amorphous carbon. However, graphite is able to slide because of the layers, meaning that is is self-lubricating.
The use of the hard, amorphous carbon creates a lot of friction when it rubs against another material. By combining the amorphous carbon and the graphite into carbon graphite material a strong, durable and self-lubricating mixture is created, offering the best of both elements.
The Ideal Combination
In addition to being resistant to wear and not requiring any external type of lubrication to avoid friction becoming a factor, the use of carbon graphite material also creates a combination that can stand up to high-temperature use.
This combination can be used when the working temperature will be 315 C for long periods of time. Different grades of carbon graphite material will have different properties for standing up to high heat over significant amounts of time.
The combination is also very corrosion resistant. This is important in many different applications and extends the life of the components that are made of this combination of carbon.
The third component in this material is the use of coal tar pitch. This is used as a binder, allowing the two forms of the carbon to stay together during the compression part of the processing stage. This will later carbonize when the molding is heated to the correct temperature for processing.