| Project/Area Number |
10555256
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| Research Category |
Grant-in-Aid for Scientific Research (B).
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| Allocation Type | Single-year Grants |
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| Section | 展開研究 |
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| Research Field |
Metal making engineering
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
SUZUKI Ryosuke Dept.of Energy Sci.& Tech., KYOTO UNIVERSITY Assoc.Prof., エネルギー科学研究科, 助教授 (80179275)
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| Co-Investigator(Kenkyū-buntansha) |
ONO Katsutoshi Dept.of Energy Sci.& Tech., KYOTO UNIVERSITY Prof., エネルギー科学研究科, 教授 (10026049)
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| Project Period (FY) |
1998 – 2000
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| Project Status |
Completed (Fiscal Year 2000)
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| Budget Amount *help |
¥9,200,000 (Direct Cost: ¥9,200,000)
Fiscal Year 2000: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1999: ¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 1998: ¥5,100,000 (Direct Cost: ¥5,100,000)
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| Keywords | iron silicide / oxidation resistance / molten salt / surface treatment / high temperature oxidation / steel sheet / concentration gradience / silicon / 耐酸化性被膜 / オゾン酸化 / 高温X線回折 |
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| Research Abstract |
A process to coat Fe_3Si-SiO_2 composite film on the mild steel was developed for corrosion and oxidation resistance. Using the molten salt, the iron silicide was deposited on the iron sheet, and its surface was then oxidized by ozone gas at the low temperature.
The molten salt consisting of KCl-NaCl-NaF-Si-SiO_2-Na_2SiF_6 was chosen because of the minimized evaporation and oxidation, and stability in air. Electroless coating on the pure iron and on the mild steel formed the smooth Fe_3Si layer over 100μm thick within 1 hour. The molten salt was trapped at the interface between silicide layer and the substrate when the growth was so rapid. No defect was fund when the iron-silicon alloy was supplied as the substrate. These findings showed that such a rapid supply of silicon ions from pure silicon to the molten salt caused the defects. The coating mechanism consisted of disproportional reaction and diffusion. Considering the growth mechanism, the α-(iron, silicon) alloy was successfully coated on iron and the layer did not contain any defects, when the aluminum-silicon liquid alloy was used instead of pure silicon. Subsequently the molten salt was replaced to the conventional salt containing pure silicon. The layer had the concentration gradient in the layer and no defects at the interface. The healthy coating was achieved by alloying silicon to control activity, or by reducing silicon ion concentration in the salt.
Similarly, the silicide layer for oxidation resistance was formed on the refractory metals such as molybdenum, niobium and nickel. A new finding was that ozone gas blowing could form Cr_2O_3 layer by producing the molten CrO_3.
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