Molybdenum Disulphide (MoS2) vs Tungsten Disulphide (WS2)
Tungsten Disulphide (WS2)
Tungsten Disulphide (WS2) is one of the most lubricous materials known to science. With Coefficient of Friction (CoF) of only 0.03, it offers excellent dry lubricity, superior to any other substance. It can also be used in high-temperature and high-pressure applications. It offers temperature resistance from -270ºC to 650ºC in normal atmosphere and from -188ºC to 1316ºC in a Vacuum. The load bearing property of coated film is extremely high at 300,000 psi.
Replaces Molybdenum Disulphide (MoS2)
Tungsten Disulphide (WS2) can be used instead of Molybdenum Disulphide (MoS2) and Graphite in almost all applications. Molybdenum and Tungsten are from same chemical family. Tungsten is heavier and more stable. Molybdenum Disulphide (Also known as Moly Disulphide), until now, has been extremely popular due to being less expensive and more available because of strong and innovative marketing. Tungsten Disulphide is not new chemical. It has been around as long as Moly and is used extensively by NASA, the military, aerospace and automotive industries.
The price of Tungsten Disulphide was approximately ten times that of Molybdenum Disulphide. However, the price of Molybdenum Disulphide has doubled every six months since then. The prices of the two chemicals are now similar and it makes sense to use the superior product, namely Tungsten Disulphide.
WS2 Improves under Pressure
Tungsten Disulphide offers excellent lubrication under extreme loads, vacuum and temperature conditions. The properties below show that Tungsten Disulphide offers excellent thermal stability and enhanced oxidation resistance at higher temperatures. WS2 is thermally stable at 93ºC more than MoS2. Another notable advantage is that the coefficient of friction of WS2 actually reduces at higher loads.
|Physical and Technical Properties Comparison|
|Properties||Tungsten Disulfide (WS2)
CAS No: 12138-09-9
|Molybdenum Disulfide (MoS2)
CAS No: 1317-33-5
|Colour||Silver Gray||Blue- Silver Gray|
|Appearance||Crystalline Solid||Crystalline Solid|
|Melting Point||1250ºC, 1260ºC (decomposes)||1185ºC decomposes|
|Density||7500 Kg.m-3||5060 Kg.m-3|
|Coefficient of Friction (CoF)||0.03 Dynamic; 0.07 Static|
|Thermal Stability in air||CoF < 0.1 until 594ºC||CoF < 0.1 @ 316ºC increases to 0.5 @ 594ºC|
|Thermal Stability in argon||CoF < 0.1 untill 815ºC||CoF increases rapidly starting @ 426ºC CoF < 0.1 @ 482ºC|
|Load bearing ability||400,000 psi for coated film CoF:0.044 @ 20,000 psi CoF reduces to 0.024 between 200,000 to 400,000 psi||250,000 psi|
|Lubrication Temperature Range||Ambient: from -273ºC to 650ºC Vacuum(10-14 Torr): from -188ºC to 1316ºC||Ambient: from -185ºC to 350ºC Vacuum: from -185ºC to 1100ºC|
|Chemical Durability||Inert Substance, Non-Toxic||Inert Substance, Non-Toxic|
|Electrical Properties||Has Semiconductor properties|
|Rockwell Hardness||30 HRc|
|Coating Film Thickness||0.5 micron|
|Corrosion Stability||Can slow down the corrosion rate, but can not fully prevent substrate corrosion|
|Coatable Substrates||Iron, Steel, Aluminum, Copper, Other Metals, Plastics and Manmade Solids||Iron, Steel, Aluminum, Copper, Other Metals, Plastics and Manmade Solids|
|Compatibility||Oil, Solvent, Paint, Fuel||Oil, Solvent, Paint, Fuel|