Tensile and creep deformation of a newly developed Ni-Fe-based superalloy for 700 °C advanced ultra-supercritical boiler applications

• Published in: Metals and materials international Vol. 21; no. 4; pp. 659 - 665
• Main Authors: Yuan, Y., Zhong, Z. H., Yu, Z. S., Yin, H. F., Dang, Y. Y., Zhao, X. B., Yang, Z., Lu, J. T., Yan, J. B., Gu, Y.
• Format: Journal Article
• Language: English
• Published: Seoul The Korean Institute of Metals and Materials 01.07.2015; Springer Nature B.V; 대한금속·재료학회
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Engineering Thermodynamics; Heat and Mass Transfer; Machines; Magnetic Materials; Magnetism; Manufacturing; Materials Science; Metallic Materials; Processes; Solid Mechanics; 재료공학; forging; transmission electron microscopy (TEM); alloys; Ni-Fe-based; mechanical properties
• ISSN: 1598-9623; 2005-4149
• DOI: 10.1007/s12540-015-4627-z

A new Ni-Fe-based superalloy, HT-X, has been developed for applications in 700 °C advanced ultra-supercritical (A-USC) boilers. The HT-X alloy is subjected to various heat treatments. Tensile tests are conducted at room temperature (RT), 700 °C and 750 °C. Creep tests are carried out under conditions of 700 °C/300 MPa and 750 °C/150 MPa. After aging treatment, the yield strength of the HT-X alloy at RT and 750 °C is 787 MPa and 624 MPa, respectively. When additional thermal exposure at 750 °C for 5400 h is applied, the yield strength is decreased to 656 MPa at RT and 480 MPa at 700 °C. For an aged specimen, the a /2 dislocation shearing process occurs when tensile testing is conducted at RT and 750 °C. As the γ’ precipitate size increases in the specimen that is thermally exposed at 750 °C for 5400 h, Orowan bowing is the dominant dislocation process, and stacking faults develop in the γ’ precipitates at both RT and 700 °C. Dislocation slip combined with climb is the dominant mechanism under the creep testing conditions. The factors that affect the mechanical properties and deformation mechanisms are discussed.