Tungsten disulfide (WS2)

Application and Technical specification

Application	It mainly has application in spraying, coating, carbon material, super rigidity material, and weld thread material, all sorts of grease, lubricating oil, friction materials and catalyses. WS2 can be applied for lubricants such as grease, oil and synthetic lubricants as an additive with powder form 1% to 15%
Technical specification	metallic-membrane plating mechanics	Taking high speed frozen compressed air as medium, pushing intensively the dry WS2 powder into the surface of base-material, WS2 molecules coalescent with base material promptly, this process need not any binding agent, and do not need bake after coating.
	Coefficient of Friction	0.030 dynamic, 0.070 static. (WS2 on WS2)
	Load Capacity	Same as substrate up to 100,000 psi
	temperature range	Lubricates from -460oF to 1200oF ( -273oC to 650oC) in normal atmosphere, -350oF to 2400oF (-188oC to 1316oC) at 10-14 Torr
	chemical stability	Inert, non-toxic
	magnetic property	Non magnetic
	hardness	Approximately 30 Rockwell C
	density	7.4 G/cm3
	thickness	0.5 microns (0.000020 in)
	color	blue and grey
	resistance to corrosion	slowing corrosion, but can’t avoid corroding base materials completely.
	coatable base materials	iron, steel, aluminum, copper and all sorts of tungsten, plastic, man-made solids
	compatibility	being compatible with a majority of oil paint, solvent, oil, fuel
	Military specification	Processed to DOD-L-85645

   Comparison between Tungsten Disulfide(WS2) & Molybdenum Disulfide (MoS2) :

   Table 1: WS₂ / MoS₂ physical and Technical Properties

Properties	WS₂	MoS₂
Colour	Silver Gray	Blue-Silver Gray
Appearance	Crystalline Solid	Crystalline Solid
Melting Point (oC)	1250oC, 1260oC (decomposes)	1185oC (decomposes)
Boiling Point		450o C
Density (Kg.m-3)	7500	5060
Molecular Weight	248	160.08
Coefficient of Friction	0.03 Dynamic; 0.07 Static
Thermal Stability in Air	COF <0.1 till 1100oF (594oC)	COF <0.1 @600oF (316oC) increases to 0.5 @1100oF (594oC)
Load Bearing Ability	300,000 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
Magnetism	Non-Magnetic	Non-Magnetic
Electrical Properties	Has Semiconductor properties
Rockwell Hardness	30HRc
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

Table 2: Comparison of the friction coefficient (μ) and the diameter of scuff scar
among three materials

Item	graphite		MoS₂		WS₂
Load(kg)	friction factor	friction vestige (mm)	friction factor	friction vestige (mm)	friction factor	friction vestige (mm)
21	0.0194	0.241	0.0194	0.268		0.197
25	0.0490	0.255	0.0204	0.270		0.250
31	0.0526	0.312	0.0180	0.283	0.0066	0.266
34	0.0601	0.316	0.0240	0.288	0.0240	0.270
38			0.0269	0.301	0.0296	0.282
40			0.0459	0.312	0.0375	0.309
44			0.0510	0.324	0.0348	0.318
48			0.0511	0.331	0.0375	0.325
52			0.0572	0.349	0.0333	0.343
56			0.0565	0.370	0.0419	0.353
61					0.0452	0.354
66					0.0448	0.361

From the data above we can conclude that basing on four-ball extreme pressure test, the item value of the average scuff scar's diameter and the friction factor is ranked as: graphite ＞ MoS2 ＞ WS2; and PB is WS2 ＞ MoS2 ＞ graphite, thus we may draw a conclusion that the lubrication performance is WS2 ＞ MoS2 ＞ graphite.