Comparative study between macrotribology and nanotribology

The behavior of different materials under macrotribological and nanotribolo gical conditions has been compared. The materials, hydrogenated amorphous d iamondlike carbon, highly ordered pyrolitic graphite, and mica, were submit ted to a fretting test (macrotribological behavior) and a combined atomic f orce microscopy/lateral force microscopy (AFM/LFM) (nanotribological behavi or). The coefficient of friction in the macroscopic regime under fixed expe rimental conditions considerably changed with the test duration, whereas th e friction coefficient measured from the nanoscopic regime was relatively c onstant during the test. In the macroscopic regime, evident wear, elastopla stic deformation, and material transfer were noticed, while in the nanoscop ic regime under the used testing conditions no wear phenomena were observed . The coefficient of friction showed some dependence on the amplitude and f requency of lateral movement of the sample relative to the counterbody in b oth the fretting and AFM/LFM tests as well as on the normal load in the fre tting test. This work leads to the conclusion that although some similitude s could be found, the macrotribological behavior of materials cannot simply be related to their nanotribological behavior due to the different wear an d friction processes. (C) 1998 American Institute of Physics. [S0021-8979(9 8)00319-3].