What exactly is molybdenum disulfide? Molybdenum disulfide, or MoS2, is a popular powdered mineral lubricant that has found wide usage in the lubricant industry. If you’ve ever wonder what is moly grease, by the end of this blog post you’ll be a moly grease expert!
When mined in its original form, molybdenum disulfide looks a lot like lead. Both are gray in color and have similar weights. Most importantly, moly is a much stronger product than lead. It is able to withstand extremely high temperatures. In fact, it has an incredible melting point of 4,370 degrees F. This high melting point is twice that of steel!
Due to its ability to withstand high temperatures, it offers high strength capabilities. Molybdenum is one of the key ingredients in the processing of the strongest and most durable of alloy steels.
Throughout the world, molybdenum disulfide is naturally found, yet in terms of it being found in large volumes, there are only a few areas in the world where it can be efficiently mined. Fortuitously, Colorado, specifically the Rocky Mountains, has become one of the prime regions for abundant mining of the molybdenum mineral. These Rocky Mountain mines produce more than 60% of the molybdenum in the world.
A lot of mining is required to produce a small volume of useful molybdenum. Over 1 ton of molybdenite ore needs to be mined to produce only 4 pounds of molybdenum. It’s a huge effort, but worth it because the black powder that is extracted offers amazing benefits to many industries. The one industry that seems to benefit the greatest is the lubrication industry.
Why Is Moly A Superior Lubricant?
Molybdenum disulfide has many useful abilities as a lubricant. It can reduce friction and wear, offers extreme pressure capabilities, withstands high temperatures, absorbs shock loading, carries heavy loads, and protects against rust and corrosion.
Molybdenum disulfide is considered a lamellar solid. Technically speaking, MoS2 has a natural molecular structure of layered crystals, or lamellae. Due to the layered crystals, MoS2 can withstand tremendous amounts of load. Through laboratory testing, its load carrying capabilities can reach up to 500,000 pounds per square inch. This far exceeds the yield point of many metals.
There are two key factors why molybdenum disulfide provides outstanding performance in the areas of friction reduction and wear reduction. First, the layered crystals of MoS2 are able to slide over one another because they offer little resistance to shear forces. Secondly, moly has an amazing ability to withstand enormous loads. When you combine its superior sliding action along with its high load carrying capabilities, you have a natural lubricant that will greatly reduce wear and friction.
Interestingly, a simplistic but effective way to illustrate how molybdenum disulfide works is to take a deck of playing cards. Put the playing cards on any table and try to apply as much pressure down on the deck of cards as you can. Notice that no matter how hard you press down on your cards, the cards will not compress beyond a certain point. Take those same playing cards an apply pressure at an angle. Then see how the cards immediately begin to slide over each other. Moly slides in a very similar way.
Molybdenum disulfide has a variety of interesting and useful properties when considering its use as a lubricant. One property is its strong attraction to metal. When pressure and heat are applied to any component that moly is asked to lubricate and protect, the layered crystals of moly will begin to plate themselves on the metal surfaces through a natural chemical bonding process.
When one looks at an exposed metal surface, it appears smooth to the naked eye. Yet, when looking at that same surface under a microscope, the actual surface is not smooth but is actually made up of microscopic hills and valleys. This fact applies to all bearing and metal surfaces. Without a lubricant keeping the two metal surfaces apart, a tremendous amount of heat and friction would obviously occur because of the two rough surfaces. The job of a lubricant is to keep these two metals surfaces apart.
At some point, because of extreme pressure or elevated temperatures, most common lubricants will break down and rupture, which leads to unnecessary wear and potentially catastrophic failure. When considering these hills and valleys and how to solve the issue of keeping these two metals surfaces apart, molybdenum disulfide has become an important lubricant in dealing with and solving this issue.
When moly is exposed to these seemingly rough metal surfaces, the lamellar solid platelets of moly will slowly over time begin to fill up those hills and valleys. Once the moly chemical bonding process is finished, there will be 23 extremely durable platelets of protective film created. The two metal surfaces now contain two powerful layers of MoS2 that will slide over each other much like how the playing cards slide, as detailed above.
Remember, one of the key features of moly is its superior shock loading abilities. Due to its ability to withstand up to 500,000 psi, one can understand how capable molybdenum disulfide is at keeping two metal surfaces from coming into contact with each other. Additionally, it can withstand temperatures up to 700 degrees F, which is beyond most lubricants. When this happens, moly literally diffuses into the bearing surfaces, which results in a much stronger alloy.
When most conventional lubricants break down over exposure to heavy loads and high temperatures, moly thrives. In other words, when the going is tough, utilizing a moly-based lubricant not only will protect components, but will in fact enhance them.
How Moly Can Be Used
What is molybdenum disulfide grease used for? A large number of manufacturers have learned the benefits of utilizing molybdenum disulfide. For example, when OEMs are making their products, a molubdenum paste or aerosol is applied to many new parts as a break-in protective barrier. One specific and well known example is the use of a moly paste or powder applied to the camshaft lobes in engines by OEMs.
In areas with high temperatures or too much dust, utilizing a dry moly in place of oil or grease is a superior choice of lubricant. Utilizing dry moly as a lubricant for chain drives, liquid oxygen valves, sleeve bearings, and electrical contacts for relays and switches, are perfect examples of where moly shines over conventional non-moly lubricants.
Space exploration is considered one of the toughest and most extreme environments that a lubricant could be asked to perform in. Interestingly, NASA has found that molybdenum disulfide has offered superior lubricating results and benefits over most other lubricants. The NASA spece program has benefited greatly through the use of moly. It has been a huge problem solver.
As already stated, it offers a wide range of lubricating abilities during extreme conditions and temperatures. It can function and lubricate at extremely cold cryogenic temperatures and it can withstand high temperatures of 750 degrees F in typical atmospheric conditions all the way through extremely high temperatures of 2,000 degrees F when asked to lubricate in the vacuum of space.
The fact of the matter is, conventional oils and greases cannot deal with the tough and difficult operating environments of space without solidifying or burning up. Hopefully you’ve learned more about this miracle mineral called molybdenum disulfide. Next, let’s take a look at what is moly grease and why making and blending a grease with moly provides the user with a superior lubricant.
What is Moly Grease?
When looking at the lubricant industry, statistics illustrate that molybdenum disulfide is predominantly used in the manufacturing of greases. Many well known OEMs such as GM, Ford, and Caterpillar recommend or use moly grease in some applications. As stated at the beginning of this blog post, it takes over 1 ton of molybdenite to extract 4 pounds of molybdenum. A lot of work is expended to extract a small amount of this amazing mineral, thus making it an expensive and costly component.
To use it in its pure powder form would be too expensive in most application. With that said, the benefits that can be achieved by using moly can far outweigh its initial cost. Its most cost effective application is when it is blended into greases. Typically, depending on the application, 1 % to 5% MoS2 is the amount required to gain excellent returns on your investment through the use of a moly disulfide grease.
You may think that using more moly is better, but it has been shown via side by side testing that a good quality moly grease can perform in a similar manner versus utilizing a lot of moly alone. Experience shows that once molybdenum has plated itself onto the metal surfaces, it can offer extended service life. Still, over a period of time, if the moly is not replenished it will slowly wear itself away. By manufacturing the proper amount of moly in grease, when lubricating a bearing, a ball joint, or any other part, the grease with moly will act as a constant reservoir of moly.
This moly grease acts as a reservoir of moly so that the molybdenum can continuously and endlessly plate and replate itself on any of the metal surfaces it is lubricating and coming in contact with. This moly reservoir will provide an endless supply of moly as long as the grease is present. If for some reason there was a complete loss of grease due to some unforeseen serious component failure, the ever present armor-like barrier of MoS2 will still be present, thus protecting the metal surfaces against friction and wear until the grease has been finally replenished.
Historical Insights of Molybdenum Disulfide
Historical records that date back as far as 1764 mention a strange gray colored mineral substance that was being used and rubbed into presses and many tools during that time period. This gray colored mineral was being carefully rubbed into metal surfaces and then polished so much that they were called “burnished black.”
Many historical records talk about a mineral that could greatly reduce friction and was quite useful in protecting metal from corrosion and rust. It is highly unlikely that this mineral was being identified with its name molybdenum because the fact is, it was not first chemically identified until many years after. With that said, the only logical conclusion for those years was that the item had to have been molybdenum disulfide.
Impressive Test Results from Moly
During the first years of the 1970s, a prominent telecommunications company was looking for a grease that could provide the necessary protection for the miniature ball bearings that were used in their miniature electric motors found in their switching systems. The greases that were being tested were non-moly and moly-based greases. These arduous tests lasted for over 4,000 hours in difficult humid conditions of 60% to 100% humidity. The purpose of these tests was to discover the effectiveness of molybdenum disulfide grease vs. lithium grease.
When the tests were concluded, all the outside components of these small electric motors were totally destroyed by corrosion and rust. The electric motors that were utilizing a non-moly grease failed way before the 4,000 hour test reached its conclusion. The miniature ball bearings that were being lubricated with moly grease were carefully examined under a microscope after being run during this extremely difficult 4,000 hour test. Incredibly, they exhibited almost no signs of pitting, rust, or wear even though the bearing were run without the protective shields in place.
Because of these promising test results, this prominent telephone company decided to switch to moly grease not only for the small electric motors, but also to lubricate their larger power generator bearings that were located all over the United States. Many of the telephone technicians were quite curious about the moly grease and had decided to conduct their own personal test to learn whether in fact the moly in the grease was the reason that the friction was being reduced.
Ultimately, what they found out was quite revealing and eye opening for them. What these technicians found out was that when temperatures were taken near the bearings at these large power generators, they noticed a substantial 35 degree F drop in temperature from the moly lubricated bearings. They concluded without a doubt that the moly grease was in fact lowering friction, which amounted to the 35 degree F drop in temperature.
Another beneficial byproduct that moly grease provides by reducing friction and heat is an increase in the life of the lubricant through a reduction in oxidation.
Another interesting test was conducted in the 1960s by General Motors research department. The goal of the tests was to find out if a non-moly grease could be improved simply by adding a small amount of moly to the grease. General Motors engineers designed a special testing apparatus that was made from Cadillac ball joints. The goal of the tests was to put the grease through wear, torque, and bearing conditions. To establish a parameter, the initial tests were done utilizing a non-moly grease. In all these initial tests, the non-moly grease failed miserably.
The next phase was a series of tests whereby engineers would add very small amounts of moly powder to the grease. Incredibly, the very simple act of just adding a very small amount of moly to the grease radically changed the test results from a failing mark to passing the test in all category conditions of torque, wear, and bearing conditions. In other words, the simple act of adding moly powder to the non-moly grease resulted in the grease now positively passing the test and correcting any of the tendencies of the grease to deteriorate or break down.
Ultimately, the General Motors engineers concluded that by simply adding 1% of MoS2 to a poor quality grease resulted in that conventional grease becoming a high performing grease.
Moly is Recommended By OEMs
Many original equipment manufacturers choose molybdenum disulfide greases to be their grease of choice. The who’s who of OEMs that use moly grease as a factory lubricant include names such as Caterpillar, Cadillac, Ford, Mercedes-Benz, Rolls Royce, Terex, and countless others. A specific example would be the Caterpillar Tractor Company. They specifically recommend only moly greases for all grease points. Their manuals specify that the moly grease must contain at least 3% to 5% MoS2.
Another example of a heavy equipment manufacturer finding a moly grease as a problem solver would be Terex. Terex owners were experiencing abnormally high wear rates with the very large king pins that were used in their articulated scraper earth movers. While testing a grease that contained 25% moly, Terex engineers were able to solve this problem.
Terex decided to go beyond 25% and had decided that for this very specific application, they were specifying a specialty moly grease that contained 75% moly.
Many more fleet operators have learned through experience that greases blended with moly will deliver countless money saving benefits for their equipment and operation. They’ve seen first hand how utilizing a moly grease will extend equipment life through the reduction in friction and wear. Additionally, a moly grease user can expect the grease to last longer, which will prolong the grease intervals. This means less time re-greasing equipment. Spending less time greasing and consuming less grease could ultimately mean more profits for any operation.
Moly Grease Delivers ROI
Changing to a moly grease requires a slightly higher investment when compared to a non-moly grease but the initial higher investment will deliver an excellent return on investment (ROI) due to less grease being consumed and less time spent having to grease equipment because of extended lube intervals.
One interesting example of how using moly grease for wheel bearings in your operation can bring huge benefits was a test conducted a few years ago by a large commercial bakery. This bakery had a large fleet of vehicles consisting of 5 semi trucks, 190 delivery trucks, and 22 vehicles for the sales force. The fleet maintenance department was dealing with a very high number of wheel bearing failures. The fleet maintenance department wanted to determine whether moly grease for wheel bearings would be a solution to their severe bearing failure issues.
To get this severe problem under control, the commercial bakery decided to test a moly grease in wheel bearings. Over a 36 month test period, the wheel bearing failure issues were virtually eliminated. This is an excellent real life example that illustrates the potential value that a quality moly grease can offer.
Another interesting test was conducted by Southwest Research Institute. During a two year period, 38 semi trucks, police cars, and city buses were lubricated with a lithium grease that was manufactured with 3% moly. In the case of the police cars, it was found that the moly grease was able to reduce chassis point wear anywhere from 26% to 38%. For the trucks and buses, there was an 18% to 88% reduction in wear for the following components: shackles, universal joints, and king pins.
The two year study showed that the moly grease substantially outperformed the same grease without moly.
Moly Grease Components
When discussing what is moly grease, one has to go beyond just moly and include some of the other components/ingredients that are needed in the manufacturing of a moly grease. There are three key ingredients that are required to make a grease.
The first necessary ingredient is the base stock oil. Typically, the volume needed of base stock oil/fluid ranges between 70% to 95%. The next ingredient needed is a thickener, where the amount needed ranges from 3% to 30%. The final component would be the additive package, whose volume can be from 0% all the way to 10%. Let’s first take a look at the base stock oils that can be used when making a moly grease.
Most lubricant blenders/manufacturers typically choose a mineral or petroleum based stock oil. For most normal operating environments, a petroleum or mineral based grease should provide satisfactory service life. When the operating environments are more extreme in both demands on both the machinery due to vast temperature ranges encountered and more difficult operating conditions, then it is best to consider a moly grease that is blended and engineered with synthetic base stock oils.
Synthetic base stock oils, due to their even and consistent molecular structure, offer much broader temperature range capabilities that go from extremely low temperatures to extremely high temperatures. Synthetic base oils are superior in terms of thermal stability and long term will offer a better return on investment versus a conventional mineral-based grease.
An example of a synthetic lubricant manufacturer offering advanced synthetic grease, including a synthetic grease with 5% moly, would be AMSOIL.
The next component we’ll look at is the grease thickener. When a thickener is blended into the base stock oil, it turns the base oil from a fluid into a solid or semi-fluid structure. The most common type of thickener used by grease manufacturers is metallic soap. These metallic soaps include lithium, aluminum, sodium, calcium, polyurea, and clay. More and more grease manufacturers are turning to the newer complex thickener-type greases. These complex thickener-type greases can offer much better load carrying abilities plus having the added benefit of withstanding much higher temperatures. In many cases they also offer superior water resistance.
These complex thickener-type greases are designed by combining a standard metallic soap such as lithium with a complexing agent like aromatic acid or boric acid. There are other unique applications where the type of thickener used in the manufacturing of grease can be a better choice than other thickener-type greases. For example, in extreme temperature environments, a grease manufactured from a thickener called bentonite clay can be used in a high temperature situation.
A bentonite clay grease is also called a no-melt grease. It is important to understand when using a no-melt grease that is manufactured with bentonite clay as a thickener that even though the thickener may not melt away during high temperatures, the base oil can only deal with so much high temperature. At some point in time, the base oil will begin to oxidize as the temperatures continue to rise. In these types of scenarios, it is important to grease more often.
The final area to discuss in terms of ingredients that go into manufacturing a grease would be the additives. When manufacturing a high quality grease, the chemist will choose additives such as rust and corrosion inhibitors, anti-oxidant additives, friction modifiers, anti-wear agents, extreme pressure additives, tackifiers, and of course in this case, the icing on the case would be molybdenum disulfide in various volumes, depending on performance requirements.
The question of what is a moly grease leads to the answer that its main function is to absorb and deal with heavy loading and to provide the ability to reduce friction and wear without causing any unwanted chemical reactions to the metal surfaces. Hopefully we have provided enough information and background to answer the question of what is moly grease. Without a doubt, flee operators can benefit greatly in making moly grease part of their maintenance toolbox. With over 70 years of proven real world experience, moly will deliver long term benefits and will become an extremely important tool in a professional’s maintenance arsenal.