Tribological behavior of dlc films in various lubrication regimes

Abstract

Owing to their attractive properties, diamond-like carbon (DLC)coatings are becoming increasingly important in the field of machine components. The extreme hardness, high elastic modulus, excellent wear and corrosion resistance, high thermal and chemical stability, and the low-friction nature of these coatings open further possibilities in improving tribological performance and reliability of different components. Despite the low friction coefficients, normally observed for DLC-coated surfaces under dry sliding conditions, only few DLC-coated tribological components are likely to be operated completely without a lubricant. There are many reasons for that. First, tribological properties of unlubricated DLC coatings are very sensitive to the surrounding atmospheric conditions, notably the relative humidity. Further, it is not always possible or economically desirable to coat all surfaces in the system, while the lubricant also serves other functions, such as cooling, in mechanical systems. Thus, the majority of DLC-coated components will continue to be operated under lubricated conditions, mainly under boundary lubrication, and will initially use the same lubricants as originally developed for uncoated surfaces. Therefore, the knowledge about DLC coatings' tribological behavior under different lubrication conditions and influence of lubricants and their constituents is crucial, if the possibilities and benefits of the DLC coatings in mechanical systems are to be fully exploited. © 2008 Springer Science + Business Media, LLC.