Durability and tribological performance of smooth diamond films produced by Ar-C 60 microwave plasmas and by laser polishing

Abstract

In this study, we explored and compared the friction and wear performance of smooth (30 nm, root mean square) and nanocrystalline diamond films (average grain size ≈ 15 nm) grown in an Ar-C 60 microwave, plasma with the friction and wear performance of laserpolished microcrystalline diamond films (grain size ≈ 20–50 μm) grown in a conventional CH 4-H 2 microwave plasma. Tribological tests were run under 2-N load in open air (30–50% relative humidity) and in dry N 2. The frictional performances of both the as-grown smooth and laser polished diamond films were comparable. They both afforded very low friction coefficients (0.06–0.15) and low wear rates (2–6 × 10 −7 mm 3/N.m) to counterface Si 3N 4 balls. We used Raman spectroscopy, electron microscopy, and atomic force microscopy to ascertain the structural, chemical, and surface topographical characteristics of the films and correlated the results with the friction and wear mechanisms of diamond films in open air and dry N 2.