FRICTION AND WEAR MICROMECHANISMS OF AMORPHOUS-CARBON THIN-FILMS

The friction and wear micromechanisms of amorphous hydrogenated carbon films were investigated experimentally using commercially available t hin-film rigid disks with sputtered carbon overcoats and Al2O3-TiC mag netic recording heads. Continuous sliding tests demonstrated the exist ence of two distinct friction and wear regimes characterized by differ ent dominant micromechanisms, Scanning electron microscopy and Raman s pectroscopy revealed that the evolution of friction in the first regim e is due to changes of the surface microtopography and the film struct ure from amorphous carbon to polycrystalline graphite. Atomic force mi croscopy showed that the topography changes result from asperity nanof racture leading to the gradual removal of carbon material and the gene ration of ultrafine wear debris. The friction behavior in the second r egime is due to various wear processes arising on the carbon film surf ace. High friction promotes surface micropitting and the formation of significantly deeper and wider texture marks. The erratic fluctuations of the friction force and microplowing of the carbon film at steady s tate are attributed to the relatively large wear particles generated b y micropitting.