Microstructural changes in DLC films due to tribological contact

The hydrogenated (a-C:H) and hydrogen free (ta-C) films were tested in sliding wear tests. The tests were carried out in air at room temperature (RH 15+/-5%). The coefficient of friction in the tests was in the range 0.03-0.12 for the a-C:H films and 0.17-0.28 for the ta-C films. The wear volume of the DLC films was sufficiently low to enable the direct comparison of the film properties of the worn film to the original film. The microstructure of the films after wear tests has been characterized by micro RAMAN, the mechanical properties were measured by nano indentation and the elastic modulus was measured with the laser-acoustic method. No change of the micro structure of the DLC films was observed. The observed reduction of the elastic modulus of the ta-C film is explained by the evolution of mechanical defects such as micro-cracks and cracking at the nodular defects typical in non filtered vacuum are depositions. (C) 1998 Elsevier Science S.A. All rights reserved.