耐熱合金の Br_2-O_2-Ar 腐食により生成したスケールの微細構造

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Hydrogen gas is among the most promising clean energy sources. A thermochemical water splitting reaction from Ca-Br-Fe system, called the UT-3 cycle, has been considered by researchers at the University of Tokyo. To produce hydrogen gas using the process, structural materials are exposed in the presence of corrosive gases such as O_2,Br_2,HBr and H_2O at elevated temperatures. Heat-resistant alloys available as a structural material often corrode markedly under low oxygen potentials at high temperatures. In the present study, microstructure of scales formed on Ni-20Cr-1Si, Fe-20Cr-4Al and Y_2O_3-coated Fe-20Cr-4Al alloys was studied in Br_2-O_2-Ar atmospheres at 1073K for 46.8 or 54.4 ks to obtain a better understanding for development of new corrosion-resistant materials. These alloys were examined under two conditions (Br_2 : 9kPa, O_2 : 5kPa, Ar : Balance, Time : 54.4 ks and Br_2 : 9kPa, O_2 : 5Pa, Ar : Balance, Time : 46.8 ks) in total pressure of 101 kPa. The color of thin scale on Ni-20Cr-1Si alloy was green, and the thin scales spalled over the entire surface during cooling under the both of corrosion conditions. Scales on the alloy were Cr_2O_3 and NiO under the both of corrosion conditions. On the other hand, the color of thin scale on Fe-20Cr-4Al alloy was mud yellow, and the thin scale was good adherence in the partial pressure of O_2 of 5kPa. Scale on the alloy were α-Al_2O_3. Marked corrosion of Fe-20Cr-4Al alloy was observed, and a part of the alloy lacked at the edge of the alloy in the partial pressure of O_2 of 5 Pa. Oxide scale on Fe-20Cr-4Al alloy was mainly Cr_2O_3. In the corrosion condition, Y_2O_3-coated Fe-20Cr-4Al alloy was covered with scales, and the scales spalled during cooling. Oxide on the alloy were Fe_2O_3 and Fe_3O_4. Residual scales on the alloy existed partially and lacking area of the alloy was not observed.
湘南工科大学の論文
1996-03-25

耐熱合金の Br_2-O_2-Ar 腐食により生成したスケールの微細構造

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