Dry lubricants are used when using a liquid lubricant would be to messy. Dry lubricants are used to reduce friction between two surfaces. Another reason you would use a dry lubricant is because the dry lubricant can withstand more heat than the liquid can. There is different materials that could be used as a dry lubricant. Some of those are graphite, hexagonal boron nitride, molybdenum disulfide and tungsten disulfide. These types of materials are great to withstanding the heat.
The three most commonly used dry lubricants that are used are graphite, molybdenum disulfide, and hexagonal BN Crucible. You would use the graphite when you are applying it to air compressors, railway track joints, and machine shop work.
That is just a few examples of what you could use a graphite for. When you are using the molybdenum disulfide it is more commonly used on space vehicles. And when you are using hexagonal boron nitride you would also apply it to space vehicles. The hexagonal boron nitride is also referred to as white graphite.
These material can operate in temperatures of 350 degrees Celsius in oxidizing environments. In reducing / non-oxidizing environments it can withstand even more heat. With the , molybdenum disulfide it can go as high as 1100 degrees Celsius.
When two objects are rolling across each other or when the two objects have to move against each other under extreme pressure, solid lubricants would be more effective than other types of lubricants. When either of these scenario would take place, a liquid lubricant would be squeezed out from between the two objects, but a dry lubricant will continue to operate smoothly.
The properties are because of the layered structure on the molecular level with a weak bond between layers. With this the layers are able to slide in relation to each other with minimal applied force. Because of this it gives them their low friction properties.
Another way that a dry lubricant is useful is for pots and pans. For example a Teflon coated pan, because it provides lubrication at high temperatures, allowing you to adequately heat food on a non-stick surface. Without having the lubricant boil away.