Bart Blanpain

Tribological behaviour of different diamond-like carbon materials

Abstract This paper comparatively studies the tribological behaviour of different types of diamond-like carbon (DLC) coatings in a reciprocating sliding wear test. The results are interpreted in terms of structure and surface morphological characteristics. At the beginning of each reciprocating sliding wear test, the higher coefficient of friction of the DLC coatings reflects the original surface conditions of contacting counterfaces, whereas the low coefficient of friction achieved under the steady regime is linked to the presence of wear debris and an enlarged real contact area. sp2 carbon bonding has been related to the occurrence of a higher coefficient of friction and surface damage of DLC materials compared to bulk diamond. The a-C coatings and ta-C films have a lower coefficient of friction at the steady regime than the a-C:H coatings, possibly due to a significant amount of hydrogen in the a-C:H coatings.

Residual stresses of diamond and diamondlike carbon films

This paper evaluated the internal stresses of different diamond and diamondlike carbon (DLC) coatings. For the diamond coatings, the stresses were determined using micro-Raman spectroscopy and x-ray diffraction (XRD), while the stresses of DLC films were determined with bent plate method. The internal stress was related to the structural properties of the coatings. Direct current plasma jet, combustion flame, and microwave chemical-vapor deposition processes were used to prepare the diamond coatings on the tungsten carbide or molybdenum substrates, while the DLC films were deposited on the silicon wafers with filtered cathodic vacuum arc process. From the Raman spectra of the diamond coatings, the compressive internal stresses were determined, which were related to the microstructure of the coatings. The results from XRD were comparable with those obtained from micro-Raman spectroscopy. Higher compressive residual stresses in the DLC films were noticed, which were also related to their chemical bonding na...