In Situ Remaining Creep Life Prediction Methods for Modified 9Cr-1Mo Steel

• Published in: Transaction of Japan Society of Spring Engineers Vol. 2023; no. 68; pp. 91 - 97
• Main Author: NAKASONE, Yuji
• Format: Journal Article
• Language: Japanese
• Published: Tokyo Japan Society of Spring Engineers 31.03.2023; Japan Science and Technology Agency
• Subjects: Chromium molybdenum steels; Creep; Creep life; Creep strength; Creep tests; Deformation; Heat resistant steels; High temperature; In situ; In-service inspection; Life prediction; Modified 9Cr-1Mo Steel; Time measurement; θmethod; Ω method
• ISSN: 0385-6917; 1348-1479; 1348-1479
• DOI: 10.5346/trbane.2023.91

The present paper proposes new remaining creep life prediction methods that can be used in situ as an in-service inspection tool for the condition-based monitoring of high-temperature structural components of modified 9Cr-1Mo steel. The methods were based on two types of the modified theta methods and the combination of the modified theta and modified omega methods and were applied to creep deformation data during creep tests made at different applied stress levels at 823K and 923 K in air. Creep lives were predicted by the proposed three methods at arbitrary time in the continuous measurement of deformation during the creep tests. The results show that the combination of the modified theta and modified omega methods gives the most accurate prediction of creep rupture time at the two levels of test temperature for different applied stress levels.