Comparing Tungsten Disulfide (WS2) with Mos2

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The problem with WS2 is it falls out of suspension much faster than MoS2 which is why it never took off as an oil additive.
 
Originally Posted By: demarpaint
The problem with WS2 is it falls out of suspension much faster than MoS2 which is why it never took off as an oil additive.


Good point. I wonder for a daily driver if that makes a difference?
 
Originally Posted By: SR1919
Originally Posted By: demarpaint
The problem with WS2 is it falls out of suspension much faster than MoS2 which is why it never took off as an oil additive.


Good point. I wonder for a daily driver if that makes a difference?



I guess it depends how quickly it falls out of suspension and if the lowest point of the oil pan is sludge free which might cause it to get caught in the sludge. I would imagine if the oil pan is sludge free and the product that falls out of suspension gets mixed back into the oil upon restarting the engine you'll be fine.
 
They are discussing dry surface applications:

Quote:
Tungsten Disulfide (WS2) and Molybdenum Disulfide (MoS2) are two of the most popular industrial dry film lubricants. Both are similar in terms of appearance, color, and high chemical durability. Both are dry lubricants, non magnetic, and are compatible with liquids such as paint, oil, fuel, and solvents.


If any company is using powdered moly or tungsten disulfides in suspension for lubricants they are living in the Stone Age.

For lubricants, we use oil soluble Ammonium Tungstates or Molydithiocarbamates.
 
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Originally Posted By: SR1919
Originally Posted By: demarpaint
The problem with WS2 is it falls out of suspension much faster than MoS2 which is why it never took off as an oil additive.


Good point. I wonder for a daily driver if that makes a difference?


Mos2 has nearly double the density of Graphite, and WWS2 is roughly double of MOS2. Yes it matters, and the thinner the oil in which it's suspended, the worse thefall outwill be.
 
Originally Posted By: Jetronic
Originally Posted By: SR1919
Here are some interesting papers on the topic of WS2 used to lower the friction properties in boundary lubrication:

Fullerene-like WS2 Nanoparticles: Superior Lubricants for Harsh Conditions

Tribological properties of WS2 nanoparticles under mixed lubrication

Ultralow-friction and wear properties of IF-WS2 under boundary lubrication



Nano-particles are a completely different beast to micron-sized particles, like used in powdered WS2


Yes I agree and I should have been more specific in my original post. Here are some examples of nano particles for sale. As you can see the cost of Mos2 vs. WS2 nano powder is the same:

Nano Lubricants

Of course you need just a few grams (1 gram per liter of oil) if you decide to use these nano particles to enhance the coefficient of friction of your engine oil.
 
So, for a 5 quart sump you're going to pay $33.00 to add something in which you don't really know if your engine's COF is really going to be affected??
 
WS² seems to work fine in bearing greases. I have mixed it (fine powder) with generic greases, and bearings with WS² run cooler. Might not work in all bearing types though..
 
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Originally Posted By: MolaKule
So, for a 5 quart sump you're going to pay $33.00 to add something in which you don't really know if your engine's COF is really going to be affected??


To estimate the worthiness of WS2 and the cost/benefit factor one has to do his/her own research based on the characteristics of the engine. The majority of cars do not need probably WS2 (my opinion) but there might be a subset of specific engines with tighter tolerances and issues with wear in the cam and other areas where it might be worthwhile to research further the applicability of WS2 nanotechnology (less than 100 nm) to provide an additional layer of protection. UOA is a must to assess the changes (if any) as a result of using WS2.

Some commercial products with Mos2 already show promise so I cannot imagine WS2 in nano form being different in my humble view.
 
From what I've read mos2 has the lowest co-efficient of friction of anything on earth.
So does tungsten disulfide beat it,or does it plate easier. What is the benefit that makes it cost so much considering mos2 can be had for under 10 bucks a can.
 
Originally Posted By: Clevy
From what I've read mos2 has the lowest co-efficient of friction of anything on earth.
So does tungsten disulfide beat it,or does it plate easier. What is the benefit that makes it cost so much considering mos2 can be had for under 10 bucks a can.


Good questions Clevy. There are a couple of interesting papers with studying the COF of Mos2 nanoparticles with PAO and WS2 nanoparticles with PAO and ZDDP (which exists in many engine oils):

Tribological Effects of BN and MOS2 Nano...der Liner Tests

Action Mechanism of WS2 Nanoparticles with ZDDP Additive in Boundary Lubrication Regime

If we were to compare Figure 1 graph in the first paper with Figure 4 in the second paper you would see that the coefficient of friction of PAO with Mos2 and PAO with WS2 and ZDDP are pretty close and very low, 0.06! Perhaps the WS2 is slightly lower than 0.06 but not by much.

In any case this is very fascinating to me specially the second paper as it concludes that there a synergy between WS2 and ZDDP to get both better wear protection and lower coefficient of friction.

As stated above all these experiments are at the nano level (less than 100 nm). I am not sure if these COFs will hold at the micro level though.
 
Years ago (1960's?) Castrol used to market its oil as having 'liquid tungsten' in it.

Apparently it caused a lot of problems, and disappeared very quickly.
 
The show illustration of the greater size (grade) particle as having 7 microns, but clearly has more than 40 micron size...
 
In the Schaeffer link:
Research done by General Motors, Ford and the Imperial
College of London has found that Soluble Moly
Compounds form very small crystals of Molybdenum
Disulfide as they come into contact with the rubbing metal
surfaces that are 0.00000001 to 0.000000025 microns in
diameter and 0.000000001 to 0.000000002 microns thick.

That is 10**-15 meter or 10**-5 angstrom thickness, the approx. diameter of a neutron or proton. Makes me wonder about the whole article; obviously off by many orders of magnitude.

Charlie
 
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