| Project/Area Number |
15360379
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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 | 一般 |
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| Research Field |
Material processing/treatments
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| Research Institution | TOHOKU UNIVERSITY |
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Principal Investigator |
KOKAWA Hiroyuki TOHOKU UNIVERSITY, GRADUATE SCHOOL OF ENGINEERING, PROFESSOR, 大学院・工学研究科, 教授 (10133050)
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| Co-Investigator(Kenkyū-buntansha) |
WANG Zhan Jie TOHOKU UNIVERSITY, GRADUATE SCHOOL OF ENGINEERING, ASSOCIATE PROFESSOR, 大学院・工学研究科, 助教授 (20323074)
SATO Yutaka TOHOKU UNIVERSITY, GRADUATE SCHOOL OF ENGINEERING, RESEARCH ASSOCIATE, 大学院・工学研究科, 助手 (00292243)
ISHIBASHI Ryou HITACHI, LTD., RESEARCHER, 日立研究所, 研究員
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| Project Period (FY) |
2003 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥15,500,000 (Direct Cost: ¥15,500,000)
Fiscal Year 2004: ¥3,800,000 (Direct Cost: ¥3,800,000)
Fiscal Year 2003: ¥11,700,000 (Direct Cost: ¥11,700,000)
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| Keywords | grain boundary engineering / stress corrosion cracking / stainless steel / sensitization / intergranular corrosion / weld decay / grain boundary control / coincidence-site-lattice boundary / 粒界構造 / 粒界腐食 / オーステナイト / クロム炭化物 / クロム欠乏 / 加工熱処理 |
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| Research Abstract |
The concept of ‘grain boundary design and control' has been developed as grain boundary engineering (GBE). GBEed materials are characterized by high frequencies of coincidence site lattice (CSL) boundaries which are resistant to intergranular deterioration of materials, such as intergranular corrosion, because CSL boundaries are low in grain boundary energy. The authors have demonstrated that a suitable thermomechanical treatment remarkably improves the intergranular corrosion resistance of type 304 austenitic stainless steel by GBE. The thermomechanical treatment increased the frequency of CSL boundaries and effectively disrupted the continuous network of random grain boundaries in the material. The homogeneous distribution of CSL segments in the grain boundary network suppresses intergranular degradations. It was also demonstrated that the thermomechanical treatment was also applicable to type 316 austenitic stainless steel and that the GBEed 316 steel showed more than four times higher resistance to intergranular corrosion than that of the 316 base steel during ferric sulfate-sulfuric acid test. The GBE drastically improved the resistance of 304 steel to stress corrosion cracking (SCC), because the base 304 steel test fractured in typical intergranular SCC mode but the GBEed 304 steel showed a small SCC in transgranular mode during an SCC test simulating the environment in a boiling water nuclear reactor. The GBEed 304 steel was also much less corrosive in transpassive environment during Coriou test. The weld decay in 304 steel was significantly suppressed by GBE. The electrochemical potentiokinetic reactivation (EPR) and ferric sulfate-sulfuric acid tests indicated quantitatively the prevention of sensitization in the weld heat affected zone. The present research project has revealed that GBE improves the resistance to intergranular corrosion phenomena extremely in austenitic stainless steels.
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