Carbon surface modifications during sliding test and friction behavior of carbon thin films against XC 48 steel

The anisotropic properties of carbon due to sp(2), sp(3), and pi bonds can lead to different carbon surfaces with different chemical, mechanical and t ribological properties. This paper reports on fundamental friction and wear mechanisms of graphite, diamond and carbon coatings: diamond-like carbon ( DLC) with nanophase diamond structure, amorphous carbon (a-C) corresponding to graphite and diamond structure, amorphous hydrogenated carbon films (a- C:H) with more graphite, and amorphous diamond film (a-D) obtained by ablat ion laser of the diamond structure. The friction coefficients mu of carbon and carbon coatings can be varied by a factor of 50 (mu=0.02-1) and the wea r rate by factor of 10(2)-10(4) according to the nature of the carbon film, the tribocontact environment, and the temperature. A compilation of the last 10 years' published studies on the mechanical and tribological behavior of different carbon coatings will be presented and d iscussed in order to specify the tribological film behavior according to it s nature and mechanical properties. The transition phenomenon from mild wea r to severe wear is investigated for each rubbing surface. Many surface structural modifications occur during friction. Scanning elect ron microscopy, X-ray analysis and diffraction electron microscopy analyses of the sliding surface will be presented and discussed. (C) 2000 Elsevier Science S.A. All rights reserved.