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Author: search.filters.author.Sakdanuphab, RachsakSubject: search.filters.subject.Corrosion

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    Changes in structural, morphological, and corrosion properties of CrN thin film effected by varying N2 pressure In the sputtering process
    (2015-01-01)
    Wongtanasarasin, Wichuda
    ;
    Sakdanuphab, Rachsak
    ;
    Suwansukho, Kajpanya
    ;
    Sakulkalavek, Aparporn
    In this study, we investigate a facet of the fabrication process of chromium nitride (CrN) film intended as a protective coating for pineapple blades. CrN thin films were deposited on unpolished stainless steel substrates (AISI304) by DC reactive magnetron sputtering in Ar+N<inf>2</inf> gases. In principle, the proportion of nitrogen partial pressure to the total pressure in the sputtering process should have considerable effects on the CrN film's chemical composition, its crystal structure, its hardness, and its corrosion resistance. We tested this supposition out by using several different nitrogen partial pressures in the sputtering process and observed the films deposited. The coatings were deposited at five different nitrogen partial pressures of 4.0×10<sup>-4</sup> mbar, 8.0×10<sup>-4</sup> mbar, 1.2×10<sup>-3</sup> mbar, 1.6×10<sup>-3</sup> mbar, and 2.0×10<sup>-3</sup>. The deposition times were controlled to achieve 5-μm thick films in each deposition. The films were analyzed by several analytical methods, such as X-ray diffraction (XRD), scanning electron microscope, micro-hardness and potentiostat in pineapple juice. The XRD spectra of the films showed face-centered cubic structure with (200) preferred orientation, positively identifying them as Cr<inf>2</inf>N and CrN thin films. The calculated d-spacing and lattice parameter of the CrN films increased with increasing nitrogen partial pressure; the ranges were 0.283-0.287 nm and 0.491-0.497 nm, respectively. The cross-section morphology of the CrN films reveals the columnar grain growth with a high density. The crystal structure and the grain texture correspond with the hardness property. The films corrosion potential, an indicator of their corrosion property, was varied from -0.14 to -0.05 volts with varying nitrogen pressure. The most corrosion resistant and the good hardness were the film fabricated at the nitrogen partial pressure of 1.2×10<sup>-3</sup> mbar.
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    The influence of N2 partial pressure on color, mechanical, and corrosion properties of TiN thin films deposited by dc reactive magnetron sputtering
    (2015-01-01)
    Nimnual, Pisitpat
    ;
    Sakulkalavek, Aparporn
    ;
    Sakdanuphab, Rachsak
    Multi-functional thin films have gained increasing importance in a decorative application. Among the available material, titanium nitride (TiN) thin film is interesting due to its golden color and mechanical resistance. Beside their properties, the corrosion property of TiN films is mainly considered in order to extend the life time. In this work, the TiN thin films were deposited on 3×3 cm<sup>2</sup> Si(100) substrates by dc reactive magnetron sputtering technique. The effects of N<inf>2</inf> partial pressure (P<inf>N2</inf>) on deposited film properties such as microstructure, surface morphology, color, mechanical and corrosion properties were investigated. We found that the crystal structure of the TiN films exhibit the (200) preferred orientation. The color of TiN films change from gold-yellow to gold-red colors by increasing of N<inf>2</inf> partial pressure that could be explained by Drude model. The TiN films have smoother surface when the N<inf>2</inf> partial pressure increases. Standard corrosion tests in artificial sweat solution show the corrosion current density (i<inf>corr</inf>) in the range between 0.25 to 4.25 μA/cm<sup>2</sup> and the polarization resistance increases with increasing of N<inf>2</inf> partial pressure. The highest hardness of the film is approximately 40 GPa with elastic modulus of 340 GPa. We conclude that N<inf>2</inf> partial pressure corelates with color, mechanical property and corrosion resistance of TiN films, which were optimized to use in decorative application.