Superhard and Low Friction Nanocomposite Coatings: Design, Synthesis, and Applications

Abstract

During last decade, there has been an overwhelming interest in the design and development of superhard and low-friction nanocomposite coatings for a wide range of engineering applications. During the same period, great strides have been made in both the physical and chemical vapor deposition technologies, and as a result, numerous coating architectures based on nano-composite and/or-layered morphologies are have become readily available in recent years. In this paper, we introduce a fundamental approache to the design and development of such coatings. Specifically, we introduce a crystal-chemical model that can help indentify the kinds of coating ingredients that are needed in such nano-composite coatings for achieving ultra-low friction and wear on sliding surfaces. Using this model, we recently designed and synthesized a series of nano-composite coatings and confirmed their superior tribological properties under both dry and lubricated sliding conditions. Employing advanced analytical tools (such as time-of-flight secondary ions mass spectrometry, x-ray photoelectron spectroscopy, and Raman spectroscopy) we ascertained the chemical nature of tribofilms forming on sliding surfaces of these nano-composite films and correlated these findings with their superior friction and wear properties. Overall, crystal chemical model used in this study seems to provide a new scientific insight into the design and production of next generation nanocomposite coatings that are ideal for harsh tribological conditions. Some of the recent field test results will be presented in support of the very unique mechanical and tribological properties of these designer coatings.