Study on SCC Initiation Mechanisms and condition mapping of High-Strength Low Alloy Steel in Boiler Water Environments

Research Project

Project/Area Number	26420704
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Multi-year Fund
Section	一般
Research Field	Composite materials/Surface and interface engineering
Research Institution	Hiroshima University
Principal Investigator	Isomoto Yoshinori 広島大学, 工学研究院, 准教授 (40127626)
Project Period (FY)	2014-04-01 – 2017-03-31
Project Status	Completed (Fiscal Year 2016)
Budget Amount *help	¥5,200,000 (Direct Cost: ¥4,000,000、Indirect Cost: ¥1,200,000) Fiscal Year 2016: ¥390,000 (Direct Cost: ¥300,000、Indirect Cost: ¥90,000) Fiscal Year 2015: ¥520,000 (Direct Cost: ¥400,000、Indirect Cost: ¥120,000) Fiscal Year 2014: ¥4,290,000 (Direct Cost: ¥3,300,000、Indirect Cost: ¥990,000)
Keywords	応力腐食割れ / 低合金鋼 / ボイラー水環境 / SCC発生メカニズム / Stress Corr. Cracking / Low Alloy Steel / Boiler Water Environment / SCC Mechanisms / Stress corr. cracking / Low alloy steel / Boiler water environment / SCC mechanisms/analyses
Outline of Final Research Achievements	Tests on stress corrosion cracking (SCC) of high-strength low alloy steels in simulated boiler water environments were conducted in order to clarify initiation mechanisms and conditions of SCC in practical boiler super-heat tubes. The simulated boiler water environments were chosen in various pH values and dissolved oxygen contents. The applied stress values before corrosion tests or relaxation loads obtained from the measurements before and after corrosion tests showed susceptibility of the SCC initiation and progression. As results, the pH values showed little, but the high dissolved oxygen did much susceptibility on SCC. The crack initiation and progression caused by hydrogen embrittlement occurred in quenched hard alloys, and the crack initiation caused by active pass corrosion occurred in quenched but a little softer alloys. The SCC susceptibility depended both the conditions of material heat treatments and specified boiler water environmental conditions.