Investigation of the Tribological Properties of Diamond Films

A chemical vapor deposition (CVD) system has been used to produce polycrystalline and nanocrystalline diamond (NCD) films. For biomedical and electronic engineering applications, it is highly desirable to deposit smooth films with decreased crystal size. In general, diamond coatings with a crystal size of 10-100 nm range are known as NCD. There are several ways in which NCD may be deposited including growth from fullerene precursors with argon dilution. Several workers have proposed various mechanisms for the growth process using inert gas dilution to conventional hot filament (HF) or microwave chemical vapor deposition (MWCVD) systems, or NCD growth through the deployment of CO₂/CO or O₂-rich gas environments. However, the use of inert gas dilution, with carbon containing species is the least complex approach to growing nanocrystalline, and more recently, ultrananocrystaline diamond (UNCD). Mechanical properties of UNCD have been determined by nanoindentation, and their nanotribological properties have been measured by nano-scratch and nano-impact testing. The relative importance of toughness (∼E/H ratio) and elastic strain-to-break (∼H/E ratio) of these systems on their behavior in nano-scratch and nano-impact tests is considered, and strategies for optimizing the deposition conditions for enhanced durability under different contact conditions are suggested in this short communication.