Types Of Dry Lubricant Powders
When two surfaces are moving in relative to each other it causes friction and wear. It is important to reduce friction and wear to improve the performance and life of the components. Therefore the moving parts have to be lubricated. Lubrication is the process of applying some material (lubricant) between the two moving surfaces to reduce friction and wear.
There are different types of lubricants like dry/solid, semi-solid, liquid and gaseous. Depending on the application the right type of lubricant can be selected. Dry lubricants can be used in powder form or can be mixed with binders and applied to the metal surfaces.
Dry lubricants are used where the operating conditions are such that lubricating oils and greases cannot form a lubricating film. Dry lubricants do not tend to pick up dust and dirt like liquid lubricants.Therefore they are preferred in applications where the contamination of the lubricant is not desirable.. Dry lubricant can be used in high temperature and high load conditions.
Dry lubricant powders can be used as additives to lubricating oils and greases to improve their lubricity and load carrying capacity. Different dry lubricants are Graphite (C) , Tungsten Disulfide (WS2), Molybdenum Disulfide (MoS2), Polytetrafluoroethylene (PTFE) and Hexagonal Boron Nitride (hBN). You can Buy dry lubricant powders online for your lubrication requirements.
Types of dry lubricants
Graphite (C)
It occurs naturally in metamorphic rocks and is the most stable form of Carbon. It has a layered structure with rings of six Carbon atoms within a layer. The bonds within the layer are strong covalent bonds whereas the layers are connected together by weak Van der Waals forces. Therefore the layers can easily slide past each other when the shear force is applied. This leads to a low coefficient of friction.
It is the most widely used dry lubricant and can be used in powder form or in suspension. It is mostly non-reactive but has good thermal and electrical conductivity.
Tungsten Disulfide (WS2)
It is classified as a Transition Metal Dichalcogenide (TMD) and has a layered structure. A layer of Tungsten atoms is sandwiched between two layers of Sulphur atoms thus forming a S-W-S structure. The bonds within the layer are strong and the layers are connected together by weak Van der Waals forces. The layers easily slide past each other and this gives WS2 good lubricating properties.
WS2 has a low coefficient of friction (0.03) and is one of the most lubricious materials. It can be used in high temperature, high pressure and high vacuum conditions. Due to its properties it is widely used in military and aerospace industries.
Molybdenum Disulfide (MoS2)
It is classified as a Transition Metal Dichalcogenide (TMD) and has a layered structure. A plane of Molybdenum atoms is sandwiched between two planes of Sulphur atoms. The bonds within the layer are strong and the layers are connected together by weak Van der Waals forces. The layers can easily slide against each other and this gives lubricating properties to MoS2.
If the coefficient of friction increases then the shear strength of MoS2 increases. This property is known as superlubricity. MoS2 can work effectively up to a temperature of 350° C in oxidising environments.
Polytetrafluoroethylene (PTFE)
It is a synthetic fluoropolymer made up of Carbon and Fluorine. It consists of a chain of Carbon atoms with two fluorine atoms bonded on each side. The Carbon and Fluorine atoms are bonded with strong covalent bonds. The Fluorine atoms surround the Carbon chain forming a protective layer and this makes PTFE chemically inert.
PTFE is hydrophobic which means that neither water nor water containing substances cannot wet it. It has high density and is resistant to high temperatures. It helps to reduce friction, wear and energy usage when used for lubrication.
Hexagonal Boron Nitride (hBN)
It is the hexagonal form of Boron Nitride and is most stable. It has a layered structure with a layer of Boron atoms sandwiched between two layers of Nitrogen atoms. The atoms within a layer are bonded with strong covalent bonds and the layers are connected together by weak Van der Waals forces. The layers easily slide against each other when a shear force is applied and this makes hBN a good lubricant.
hBN can be used as a lubricant at low and high ( 900° C in oxidising environments) temperatures. It is also called ‘White Graphite’. It is used in place of Graphite where the reactivity of Graphite is not acceptable. hBN can be added to alloys, ceramics, plastics and rubbers to improve their self-lubricating properties.
