Dry lubricants do not use a liquid media, but are able to provide
lubrication while remaining in a solid state. Also called solid
lubricants, dry lubricants can have high oxidative and thermal
degradation resistance. Some advantages that dry lubricants provide
include the ability to perform at extreme temperatures that would cause
liquids to evaporate or freeze as well as clean operation because dirt
and debris will not stick to solids like they would to liquids such as
oil or grease.
Able to act as both a lubricant and a sealant, dry lubricants are often used in applications such as slide mechanisms, air compressors
, railway track joints, space vehicles, catheters, bearings, circuit boards and transducers. Often referred to as a film or coating, dry lubricants bond to the surface of the machine or part and, as a result, offer a longer wear life than liquid lubricants, such as lubricating oil
, which can be difficult to apply and retain. Lubricating oils do have their advantages though, including the fluidity to be stored in a system and replenish a supply automatically, such as oil within cars. Typical industries that benefit from the use of dry lubricants include aerospace, electronics, automotive, medical, petrochemical, industrial, food processing and agricultural. Dry lubricants consist of four common materials, which are hexagonal boron nitride, graphite, molybdenum disulfide, PTFE and other less common, materials such as tungsten disulfide, talc, calcium fluoride, silicone and cerium fluoride.
The lubricating properties of the major materials used to produce dry lubricants result from the weak bonding of layers on the molecular level. This weak bonding results in sliding when minimal force is applied, resulting in extremely low friction properties. Dry lubricants are applied to materials through spraying, tumbling, dipping, wiping or brushing, although spraying and dipping are the two most common methods, followed by thermal curing in order to provide bonding. Dry lubricants can be applied to numerous materials including rubber, glass, wood, copper, chromium, aluminum, stainless steel, plastic and titanium. In addition to being used to reduce friction between two moving parts that are in contact, dry lubricants can also serve as a back-up to liquid lubricants. For instance, a dry film lubricant can be placed under a grease lubricant in case there is a problem with the grease. Sometimes a lubricant can be applied incorrectly or be forgotten, which could be catastrophic for a machine without the dry lube back up in place.