Tribology: The Science of Oil and Lubrication

What Is Tribology

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Tribology is the study of lubrication, wear, and friction. In order to understand how Cool-X works, you need to understand some of the basic principles of tribology.

The primary function of an oil lubricant is to reduce friction between two solid surfaces in contact with each other. Metals are crystalline structures, and they are not typically smooth or flat at any scale, particularly at the micron or nanoscale. Without going into theory at depth, friction is the sum of all the resistance of individual points of contact between two metal surfaces.

Oil functions as a layer in between the metal surfaces, that as a liquid, offers less resistance to movement, and as a layer, separates the metal surfaces, preventing direct metal to metal contact. There are fewer points of contact, with less resistance, generating less heat and requiring less energy to move.

To make an engine or gearbox more efficient, you want to reduce friction, either by improving the surface finish, reducing the number of points of contacts, or by increasing the size of the boundary layer of oil. Cool-X works in a number of ways to improve oil properties and reduce friction.

Burnishing and the Role of Surface Finish

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Cool-X Nanoparticles act like mini ball bearings rolling the surface flat

Cool-X Nanoparticles act like mini ball bearings rolling the surface flat

The surface finish of metals has a direct correlation with friction. Smoother surfaces generate less friction. There are fewer points of contact (asperities) with less magnitude that require less force to overcome. Surface finish is normally measured by expressions like Ra, an integral of the area above or below the mean surface height divided by the surface area. Improvements in tolerances and surface finish are one of the main ways that engine fuel economy  has improved over the past thirty years.

Cool-X nanoparticles burnish metal surfaces. The photo shows two cam carriers that ran for a year for a race team in the SCCA. The cam on the left was burnished by Cool-X, the one on the right showed normal pitting, oxidation, and corrosion. The Cool-X nanoparticles burnished the cams. Burnishing – also called honing – is a process of flattening, where the surface is “pounded flat” without removing material. It is not an abrasive process. The Cool-X nanoparticles act like mini ball bearings, and when under pressure flatten the metal surfaces. Note that this is a gradual process – the Cool-X nanoparticles are dispersed in the oil in very small quantities (by weight) and while they have the surface area of 10 football fields, most of them are not in contact with the metal at any given point. In practice, we have found that burnishing may first be noticeable after 30 or 40 hours of use under load, but will continue for 30K – 40K miles of driving in a diesel engine.

The burnishing process has a second effect. It strain hardens the metal surfaces. Metals deform by fracturing along fault lines in their crystaline structure. When these fault lines are disturbed by burnishing, it prevents cracks from propagating, and makes the crystalline structure more stable. This is the same process used in cold welding fasteners, or by medieval swordsmiths repeatedly pounding their blades flat. The end result is that the surface of the metal becomes much harder, difficult to break, and thus resistant to wear. This is an excellent outcome for gears, pistons, and tappets subject to repeated stresses in a hot engine, as it prevents warping and parts from breaking.

There are several studies showing how nanodiamonds can be used to harden metals. Note that the carbon nanoparticles do not appear to lodge in the metal or create a layer on the surface, which is different from the results you get using carbon vapor deposition techniques. In some ways, this could be described as a poor man’s CVD coating – Cool-X is much less expensive, yet achieves similar results over time as the burnishing process unfolds.

Oil Additives

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Oil performance has improved dramatically over the last thirty years because new, more efficient oil additives have been developed. In a modern engine oil, the additive pack represents 20% of the volume and more than half the cost. All lubricating oils have additives. Most are used for these purposes:

  • viscosity modifiers (designed to keep cold oils from congealing and hot oils from becoming to thin)
  • detergents (designed to force contaminants (metal bits, dirt, ash) to drop out of suspension in the oil, keeping it clean).
  • Antiwear additives (designed to maintain lubricity and reduce friction when metals are rubbing with force and the oil layers aren’t sufficient to keep the parts from seizing)
  • Anti-oxidants (designed to prevent oil additives from oxidizing, and to neutralize the acids that form with oxidation)
  • Surface tension modifiers, designed to “wet out” metal parts and promote the formation of a good oil film boundary layer

For more information about oil additives and their purposes, click <here>.

Cool-X nanoparticles serve as an antiwear additive, antioxidant, and surface wetting agent, in addition to burnishing and improving thermal conductivity. Equally important, they are chemically stable, and unlike current chemistries, won’t break down in the high heats found in today’s engines. Nor do they aggregate, react with acids, or fall out of suspension. This durability makes them unique, and provides oils with Cool-X with exceptional durability as they age.

Please note that we agree with those who say that there are few reasons to buy oil additives off the shelf. Certain old cars require ZDDP as an anti-wear additive, which has been banned from formulations for new vehicles. Otherwise, it is cheaper to buy oil already formulated with the additives necessary already included. Cool-X is an exception, however. Our technology is not included in the additive packs sold by Lubrizol or Afton; neither the additive nor the oil companies have expressed much interest in a technology that doubles or triples oil life.

Oil Condition and Break-down

Skip an oil change with Cool-X

Skip an oil change with Cool-X

 
 Do you change your oil every 3,000 miles? Or because an algorithm in the car’s onboard computer told you that it was time to change your oil? These are all based on very conservative estimates of oil life, and in no way reflect the likely true condition of the used oil in your engine. New has been developed which measures the electrical impedence of the oil, based on its acidity and other factors, which can be used to track oil condition.
Oil breaks down because its additives break down or it becomes contaminated with water, metal bits, dirt, or ash. The underlying cause for oil break-down is almost always excess heat, which lets chemicals oxidize, weakens metals, polymerizes oil, or breaks down seals. An industry rule of thumb is that for every 18F (10 C) reduction in oil temperature, the oil will last twice as long. Cool-X, by , significantly extends oil life. And now that it is possible to inexpensively test oil condition, Cool-X can add value by allowing you to defer oil changes until your oil really needs to be changed, and not just follow a dumb algorithm.

Knowledgebase

  • MSDS
  • HD Truck Presentation
  • Trifold Brochure
  • FAQs
  • Surface Finish Presentation
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