A study of the effect of ionization efficiency during deposition on the properties of chromium PVD films

Thin chromium films were deposited on metallic substrates by vacuum evaporation, diode ion plating, and thermionically assisted triode ion plating. Ion plating was performed under cathode bias voltages range from ;An experimental program was designed to make a systematic and significant study of the effect of ionization efficiency on the film properties. The specimen which has the highest ionization efficiency by changing the only variable in each group was chosen as the standard and significant comparisons of all the film properties were made in terms of the relative ionization efficiency.;Chromium PVD coatings were characterized by x-ray diffractometry, scanning electron microscopy, Auger electron spectroscopy and microhardness measurements. The results showed that as ionization efficiency increased in the coating processes of all four groups, the coatings have less contamination of oxygen and carbon. The increased ionization also improves the substrate coverage and promotes an equiaxed structure. The effect of increasing ionization on the texture of the coatings was evaluated by studying the variation of the percentage intensity of (110) reflection in each group. The result showed that more randomly oriented crystallographic microstructures were obtained with increased ionization.;These coatings were then tested in one normal sulfuric acid and 0.1 M sodium chloride solutions to determine their corrosion characteristics. The results of these tests showed that substrate coverage and thus the protection of the base material was generally improved as ionization was increased during deposition. In addition, a new electrochemical test relating the porosity of the film has been developed. Specific test solution and electrode potential were chosen so that the chromium coatings were in passive region and the substrates were in active dissolution region if they were in contact with the test solution. The results of these tests corresponded well with the results of the film microstructures. (Abstract shortened with permission of author.)...