STRUCTURES AND PROPERTIES OF DISORDERED BORON-CARBIDE COATINGS GENERATED BY MAGNETRON SPUTTERING

Disordered boron carbide coatings with their high hardness, high lubri city, and low surface friction have become the coatings of choice to e nhance the wear performance of man!, existing products. These coatings have been successfully commercialized using a magnetron sputtering pr ocess. In this paper, the effects of one of the critical process param eters, bias voltage, on the chemistry, microstructure, and the propert ies of the coatings are discussed. In combination with microstructure examination, special emphasis was made on nanoscopic level chemical an alyses in order to explain the effects of this process parameter. The substrate bias was found to have strong effects on the hardness and th e stress of the coating, but it has little influence on the frictional characteristics of the coating. The results of the examination and th e analyses of the coating using FTIR, XPS, TEM, PEELS, and SIMS reveal ed that the morphology of the coating changed from a columnar structur e to a continuous solid structure as the substrate bias voltage increa sed from 0 to 200 V. Oxide species were found in between the columns, while the columns mainly consisted of boron carbide with a boron to ca rbon atomic ratio of about 4. The atomic ratio of boron to carbon appe ared to be independent of the substrate bias. (C) 1998 Elsevier Scienc e S.A. All rights reserved.