The tribological characteristics of diamond-like carbon films at elevated temperatures

To determine whether diamond-like carbon (DLC) films could be applied as a kind of solid lubricant coating at high temperatures, the friction properti es and wear ability of DLC films in sliding against alumina at elevated tem peratures up to 400 degrees C were investigated. We used Raman spectroscopy to determine the chemical and structural changes of DLC films, a scratch t ester to investigate the variation of the adherence between DLC films and t he silicon wafer substrate, and scanning electron microscopy (SEM) to obser ve the wear tracks at different test temperatures. We confirmed that chemic al-vapor-deposited DLC films are good lubricant and wear resistant films wi thin a suitable temperature range. Increasing the temperature decreased the friction coefficient and increased the wear rate of DLC films. These pheno mena an due to film graphitization as revealed by Raman spectroscopy. Above the critical temperature of 300 degrees C, films peeled olf quickly, i.e. their wear lives are shortened, since the adherence between film and substr ates abruptly decreased tit high temperatures. Below 200 degrees C, the dom inant film wear mechanism is plastic deformation. At 300 and 400 degrees C, the dominant wear mechanisms of DLC films are fracture and delamination. ( C) 1999 Elsevier Science S.A. All rights reserved.