Using the general principles of a crystal chemical model [1], we have recently formulated a series of novel nanocomposite coatings that can provide very low friction and extreme resistance to wear and scuffing under sever boundary lubricated sliding conditions. These coatings essentially consist of a soft metallic and a hard nitride phase; both of which are strategically formulated to react favorably with some of the additives in engine oils and hence to result in very protective, low-shear boundary films. The kinds of boundary films that form on the sliding surfaces of these nanocomposite films are extremely resistant to wear and scuffing. In a series of scuffing tests, we were unable to scuff these nanocomposite films under sever contact pressures that caused significant plastic flow in substrate steels. The results of this study suggest that these novel nanocomposite coatings have the potential to meet the increasingly stringent application conditions of future engine systems including ring and liner assembly, gears, tappets, bearings, and other power and drivetrain components. In this paper, we will introduce the main characteristics of these novel nanocomposite coatings and present the fundamental tribological mechanisms that control their superior friction, wear, and scuffing behavior under severe boundary lubricated sliding conditions. Principles of crystal chemical model that was used as a guide in the formulation of these nanocomposite films are also presented. This model provides a scientific means to better design and formulate future tribological coatings that provide not only low friction but also extreme resistance to wear and scuffing.

¹A. Erdemir, A Crystal Chemical Approach To the Formulation of Self-Lubricating Nanocomposite Coatings, Surface and Coatings Technology, in press 2005.

PVD and PACVD coatings in automotive applications have so far been mainly used for low wear applications. The good frictional behaviour has been a key asset. Applications utilizing this property are still increasing. The trend in coatings applied is converging.

It is believed that the coating applications will further broaden in automotive, if PVD-PACVD coatings can bring a proper corrosion performance. Unlike low friction coatings the technical solutions are still widely diverging. An overview will be given of present development of corrosion inhibitors. Furthermore a number of practical examples will be given, of parts being coated, with one of the main requirements a proper corrosion protection.