Diamond-like carbon (DLC) films were synthesized by a combined PVD and PECV
D process to produce a multilayered structure consisting of a Ti interlayer
, a graded transition layer, and the carbon film. The oxidation behavior of
DLC films was investigated using thermogravimetric (TGA) and differential
thermal analyses (DTA). The phase identification and microstructural examin
ations were conducted by XRD, Raman and SEM/EDS. According to those results
, DLC films disintegrated at 350 degrees C, showing typical graphitic trans
formation and oxidation behavior. The weight loss as a result of oxidation
of carbon followed a linear reaction rate of -2.3 x 10(-4) g/min cm(2). At
450 degrees C, oxidation of the underlying TiN/TiCxNy interlayer occurred i
n addition to the oxidation of DLC. Weight gain caused by the formation of
TiO2 was observed. The overall oxidation kinetics of DLC is close to a para
bolic behavior with k(p)=5.48 x 10(-5) mg(2)/cm(4) h. Surface cracking of t
he film resulted from stress relief. The microhardness of DLC films decreas
ed with increasing annealing temperature due to the graphitization and oxid
ation of DLC. The transition temperature was confirmed using the results fr
om the Raman analysis. (C) 1999 Elsevier Science S.A. All rights reserved.