CORROSION AND MECHANICAL STUDIES OF CHROMIUM NITRIDE FILMS PREPARED BY ION-BEAM-ASSISTED DEPOSITION

Chromium nitride films are known as good protective layers for both co rrosion and wear attack. In the case of corrosion protection in partic ular they are expected to be superior to comparable titanium nitride l ayers. Therefore they are very interesting as a partial or complete su bstitute for the ''classical'' electrolytically deposited hard chromiu m coatings that have been in use for decades, an issue more and more c ritical from an ecological point of view. As it is not possible to syn thesise chromium nitride, as in the case of titanium nitride, by simpl y evaporating chromium in a nitrogen atmosphere, the layers had to be prepared by evaporation and simultaneous irradiation with nitrogen ion s. Hereby the main parameter determining the composition and propertie s of the films is the arrival ratio of impinging nitrogen ions to cond ensing chromium atoms (I/A). The formation of chromium nitride was pro ved by means of Auger electron spectroscopy and additionally by corres ponding X-ray diffraction (XRD) measurements. Compared with pure chrom ium deposited under argon irradiation, these coatings show a compressi ve instead of a tensile stress as measured in situ with the bending ca ntilever method and subsequently will be investigated with XRD. Corros ion tests and hardness measurements with the films on metal substrates were also performed. Taking into account the optimisation possibiliti es of the ion-assisted-beam deposition technique, these results indica te very promising potential for future applications. (C) 1998 Elsevier Science S.A.