Moly and Graphite
- Thread starter willbur
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It has been my understanding graphite needs a little moisture for it to lubricate(?)
This is what an internet search turns up.
Molybdenum disulfide (moly) and graphite are added to grease primarily to act as solid lubricants that provide extreme pressure protection and reduce friction in applications where the base oil film might be squeezed out or under heavy shock loads.
These additives function by forming a protective coating on metal surfaces; moly's laminar sheets and graphite's layered structures allow them to slide easily over one another, preventing metal-to-metal contact even when the grease's oil component fails. They are specifically used in high-load environments like journal bearings, fifth wheels, and pivot pins to fill microscopic imperfections and prevent wear, scoring, or "welding" of surfaces.
While both serve as solid lubricants, they are chosen based on specific environmental needs:
- Molybdenum disulfide is preferred for wet, high-pressure conditions because its particles cling tightly to metal surfaces, offering superior adhesion and anti-wear properties in muddy or submerged environments.
- Graphite excels in dry, high-temperature scenarios (up to 450–500°C) where it remains effective after base oils evaporate, though it lacks the same adhesive quality as moly.
- Combining them in a single grease formulation creates a durable lubricating film capable of withstanding severe loads, constant friction, and harsh contaminants that standard greases cannot handle.
But with few exceptions, greases do not contain water. Water may be added or formed during the soap reaction, However, most greases go through a dehydration process. During processing, moly and graphite (and other filler or lubricating solids) are dispersed into discrete particles that are in an oil-soap matrix.
I ment as it is being used. Moisture in the air supplies what the graphite needs to work is my guess. In very arid conditions, the moisture is probably absent and the moly takes over. I think the moly provides a very hard surficial coat on the metal surfaces while the graphite fills in the metal pores forming a super slippery surface(?). Together they make a great general purpose grease for environmental coverage. Just my opinion and best guess
wouldn't the grease keep moisture out thus preventing rust and corrosion?
Graphite-fortified greases are typically meant for extremely high temperature industrial applications. It isn’t really necessary in automotive applications.
I believe that very low levels of moisture are usually sufficient to keep the graphite working. From what I've seen, a significant difference in friction shows up only under vacuum conditions. Graphite is also more thermally stable, as noted by others, and less expensive.
Thank you.
I have seen tubes of CRC Industries Moly-Graph grease in Walmart. I guess its the place to go for steel furnace heat proof grease LOL why combine it with moly?
Besides Stalube Molygraph is this even a thing? That grease has identical specs to $6 Supertech Moly grease (likely the same thing relabeled being CRC made) and I’ve also heard one of (many) Ford spec moly greases is also relabeled CRC Molygraph. This is basically a low temp 1% moly chassis grease known to perform well in ball joint/tie rod end applications. I’m sure if that 1% graphite made a real difference in this light duty low cost middling spec’d grease WAY more greases would be on the bandwagon. And that’s not a shot. I use it or Valvoline multi purpose grey 1% moly grease in all ball joint/steering applications. Cheap, plentiful at any harbor freight $8.99 and LONG history of effectiveness when used where it belongs. I believe they put it in simply because they also make one of the most popular dry graphite spray lubricants available so adding 1% to a grease is nothing to THEM.
I'll offer my non-expert opinion to say that, yep one of the functions of grease is to create a semi-solid barrier to moisture. The big problem with most greases is, most of them eventually dry out, at which point they are no longer protecting much of anything. Of course it all depends on the properties of the grease - which is yet another reason why there isn't one grease for everything.
Ok here is a brief breakdown of why you would use solid lubricants moly, graphite or other newer solid mixtures.
First the main purpose of graphite and or moly is to increase load carrying capacity. There is always a downside though and solids take up space thus the name solids. So in high precision bearings this can be an area of concern. Graphite typically has a much smaller grain structure and has better lubricity at normal operating temperature.
Moly had a larger structure making it less ideal for high precision applications. Also as mention in a earlier post moly works excellent over 400C but its a solid at lower temps. So application is very important to consider.
When I spec a grease to a customer understanding the application and environment is critical. If there is a high level of corrosion. I focus on the additives other than moly or graphite. There's polymers and anti oxidants that can help there among other ingredients.
Then we have modern calcium sulphonate complex. The calcium soap is a sort of solid lubricant on its own and actually improves in load carrying when mixed with water to an extent. This is why you find higher weld loads and load carrying properties. The issue is these soaps harden when loaded with water and they can eventually act like sand and smoke a bearing in a hurry if not purged.
There's no one solution that's perfect we use all these make lubricants.
But this may make it easier for some to quantify. Think this way. When you have a pin or bushing type joint solids are your friend when you have high pressure sliding movements thus why they are used heavily in heavy equipment. But if your using anti friction or ball bearing type bearings the correct oil viscosity is you best bet and in extreme cases and environments you amy add solids. But if you put a heavily loaded moly grease into a tight tolerance bearing you may wear it out faster with moly and then extend its life with the moly once damage has occurred.
We also have some really interesting products now that act as almost a ceramic coating for the surface of the steel so they dont help once the part is in failure mode like moly or graphite, it will extend the life of the part under normal conditions exponentially.
First the main purpose of graphite and or moly is to increase load carrying capacity. There is always a downside though and solids take up space thus the name solids. So in high precision bearings this can be an area of concern. Graphite typically has a much smaller grain structure and has better lubricity at normal operating temperature.
Moly had a larger structure making it less ideal for high precision applications. Also as mention in a earlier post moly works excellent over 400C but its a solid at lower temps. So application is very important to consider.
When I spec a grease to a customer understanding the application and environment is critical. If there is a high level of corrosion. I focus on the additives other than moly or graphite. There's polymers and anti oxidants that can help there among other ingredients.
Then we have modern calcium sulphonate complex. The calcium soap is a sort of solid lubricant on its own and actually improves in load carrying when mixed with water to an extent. This is why you find higher weld loads and load carrying properties. The issue is these soaps harden when loaded with water and they can eventually act like sand and smoke a bearing in a hurry if not purged.
There's no one solution that's perfect we use all these make lubricants.
But this may make it easier for some to quantify. Think this way. When you have a pin or bushing type joint solids are your friend when you have high pressure sliding movements thus why they are used heavily in heavy equipment. But if your using anti friction or ball bearing type bearings the correct oil viscosity is you best bet and in extreme cases and environments you amy add solids. But if you put a heavily loaded moly grease into a tight tolerance bearing you may wear it out faster with moly and then extend its life with the moly once damage has occurred.
We also have some really interesting products now that act as almost a ceramic coating for the surface of the steel so they dont help once the part is in failure mode like moly or graphite, it will extend the life of the part under normal conditions exponentially.
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