when is graphite used as a lubricant
Answers
Graphite, thanks to its peculiar microstructure composed of hexagonal planes of hybridized sp2-sp3 carbon carbon bonds, has very good lubricating properties. Interlayer bonds are weak so the material tends to flake easily. The single flakes are very thin (to the limit of being graphene) and can easily position themselves between two surfaces in reciprocal motion generating a situation of three-body wear (surface-graphite-surface) with very low coefficients of fritcion. It is used, as a lubricant, mainly in two ways.
Powders
Graphite powders are added ad a solid lubricant in lubricating sprays and in industrial oils used for technical applications (for hot forging/stamping and to keep lubrication in mechanical gears, for example). This is overall the most frequent use. Handling is easy, fluidity is high, they are just very dirty and tend to stick to anything. Easy to wash away in soap.
Bushings
Bronze bushings where only dry lubrication is permitted are frequently modified with graphite inserts to create bronze-graphite composite bushings as the image below. These guarantee a low coefficient of friction without the use of oils and other liquid lubricants.
Another interesting application is to add it to the powders from which sintered bronze bushings are produced. There are powder metallurgy products used wherever there are rotating or oscillating shafts.
If the mechanical forces aren't too demanding it can also be used directly in the form of a sintered graphite bushing.
Answer:
Graphite, thanks to its peculiar microstructure composed of hexagonal planes of hybridized sp2-sp3 carbon carbon bonds, has very good lubricating properties. Interlayer bonds are weak so the material tends to flake easily. The single flakes are very thin (to the limit of being graphene) and can easily position themselves between two surfaces in reciprocal motion generating a situation of three-body wear (surface-graphite-surface) with very low coefficients of fritcion. It is used, as a lubricant, mainly in two ways.
Powders
Graphite powders are added ad a solid lubricant in lubricating sprays and in industrial oils used for technical applications (for hot forging/stamping and to keep lubrication in mechanical gears, for example). This is overall the most frequent use. Handling is easy, fluidity is high, they are just very dirty and tend to stick to anything. Easy to wash away in soap.
Bushings
Bronze bushings where only dry lubrication is permitted are frequently modified with graphite inserts to create bronze-graphite composite bushings as the image below. These guarantee a low coefficient of friction without the use of oils and other liquid lubricants.
Another interesting application is to add it to the powders from which sintered bronze bushings are produced. There are powder metallurgy products used wherever there are rotating or oscillating shafts.
Explanation: