Coatings and Lubricants:
Super-Hard and Ultra-Low-Friction Films for Friction
and Wear Control

Ali Erdemir researches nanolubricants.

The many rolling, rotating and sliding mechanical assemblies in advanced transportation vehicles present friction and wear challenges for automotive engineers. These systems operate under severe conditions—high loads, speeds and temperatures—that currently available materials and lubricants do not tolerate well. Improving the surface friction and wear characteristics of the mechanical system components is an opportunity for engineers, and the use of super-hard, slippery surface films offers promise.

Argonne scientists have developed a number of smooth, wear-resistant, low-friction nanocomposite nitride and diamond-like carbon films that have exceptionally low friction (coefficient of 0.02 to 0.05); such films permit the smooth and safe operation of mechanical assemblies in transportation systems by reducing wear and parasitic friction losses. Specifically, Argonne researchers have found that diamond-like carbon films can be very useful for demanding applications in fuel injectors, piston pins, rings, liners, bearings, gears, tappets and a variety of other drive- and power-train components involving rolling, sliding and rotating contacts.

Combining extreme hardness with ultra-low friction, superhard and low-friction nanocomposite nitride coatings can provide long-term wear resistance and lubrication, thus reducing material and energy losses in engines. The main components of these nanocomposite films are highly reactive with additives in oils, which results in low-shear boundary films that protect sliding surfaces against wear and scuffing and provide extremely low friction coefficients. Other advantages include:

• Increased lifetime and improved performance in rolling, sliding and rotating automotive components
• Extreme resistance to wear and scuffing
• Extremely slick coatings for sliding engine parts in engines

The low friction of diamondlike carbon films is associated with the materials’ inert nature; these materials do not stick to rubbing surfaces. Additionally, because of the strong covalent bonding between carbon atoms, the wear rates of these materials are extremely low.

Argonne is currently demonstrating the superior friction and wear properties of the films for a wide range of engine applications. Researchers are also developing methods for applying the films to metal-cutting and -forming tools for a variety of manufacturing applications.

More

• Illinois Center for Advanced Tribology brochure (561 kB pdf)

April 2008