| Co-Investigator(Kenkyū-buntansha) |
KOTERAZAWA Keiji Himeji Institute of Technology, Faculty of Engineering, Professor, 工学部, 教授 (50047594)
INOUE Shozo Himeji Institute of Technology, Faculty of Engineering, Assistant Professor, 工学部, 講師 (50193587)
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| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1997: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1996: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Research Abstract |
TiN films as a representative dry coating are very hard, so they are highly resistant against wear and corrosion, and furthermore their appearance is attractive gold-like color. Due to the presence of micro-defects, however, they are usually unsuited for corrosion-resistible applications. In particular, the so-called perforating pinhole defect impairs the environment shielding effect of TiN film, and there are many problems remaining in connection with improving the corrosion resistance of the substrat. In orter to minimize pinhole defect density in a TiN film, the process parameters must be adequately controlled, for this to happen, a quick and quantitative evaluation method of pinhole defect must be developed. In this study, therefore, the critical passivation current density (CPCD) method was used to evaluate pinhole defects quantitatively as the defect area ratio for the TiN-coated stainless steels prepared by the r.f.reactive sputtering. The main results obtained can be summarized
… More
as follows :
The -0.5mum thick TiN-films deposited at the N_2 flow-to-total flow ratio F_<N2>/F_<total> of 0.4 and above were with the characteristic gold-like color. They exhibited the columnar structure, of which the preferential orientation changed from<220>to<111>direction with an increasing F_<N2>/F_<total>. Here, the electrochemical evaluation of pinhole defects is focused on the TiN films deposited at F_<N2>/F_<total> of 0.4. The critical passivation current density i_<crit> in the TiN-Coated stainless steels decreased considerably with an increasing film thickness, and the resulting corrosion resistance was improved remarkably by TiN-coating. Above 1.5mum in thickness, however, there was an increasing tendency in i_<crit> with cracking and/or peeling. The area ratio of pinhole defects was evaluated by the ratio of i_<crit> of a coated and a non-coated specimen, i.e., by the CPCD method. The result coincided well with the true defect area ratio based on the optical micrographs before and after polarized anodically. Consequently, such electrochemical measurement is superior as an evaluation method for the pinhole defects of corrosion-resistible coating. Less
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