Analysis of (Cr,Mo) Oxycarbide Films Grown on Stainless Steel via Metalloorganic Chemical Vapor Deposition
Resource
Journal of the American Ceramic Society 80 (4): 886-892
Journal
Journal of the American Ceramic Society
Journal Volume
80
Journal Issue
4
Pages
886-892
Date Issued
1997
Date
1997
Author(s)
Lo, Ming-Hung
Abstract
A mixture of hexacarbonyl of chromium and molybdenum ((Cr,Mo)(CO)6) was used to deposit oxycarbide films on stainless steel at temperatures of 175°-450°C. Through the analysis of deposition kinetics in various temperature regions, the controlling mechanism was determined to be exothermic surface reactions. Activation energies of the low- and medium-temperature regions were determined to be 71.2 and -60.1 kJ/mol, respectively. Some properties - including densities, composition, and crystalline phases - of the films were investigated. Results revealed that the chromium content of coating products increased as the temperature increased. The dominating surface reactions switched as temperature increased, because of the increase of chromium content in the precursor gas. Hence, the coating rate and density increased to a maximum, then decreased as the coating temperature was increased to >275°C. Deposited phases were determined by X-ray diffractometry, and the relationship with film density phases has been discussed, using their microstructural textures from scanning electron microscopy micrographs. Corrosion resistance was measured by an electrochemical method. The films obtained in the low- and medium-temperature regions improved the corrosion resistance of stainless-steel substrates by a factor of 24. In addition, the latter case showed the effect of passive protection and was an optimized selection for corrosive protection. The relationship of the improvement of corrosion resistance, physical properties, and the contribution of composed phases was discussed.
Other Subjects
Activation energy; Carbides; Corrosion resistance; Electrochemistry; Film growth; Metallorganic chemical vapor deposition; Protective coatings; Reaction kinetics; Scanning electron microscopy; Stainless steel; Thermal effects; X ray diffraction analysis; Chromium/molybdenum oxycarbide films; Exothermic surface reactions; Ceramic coatings
Type
journal article
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