Evolution of Carbide Precipitates in 2.25Cr-1Mo Steel during Long-Term Service in a Power Plant

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 2010-06, Vol.41 (6), p.1441-1447
• Main Authors: Yang, Yong, Chen, Yiren, Sridharan, Kumar, Allen, Todd R.
• Format: Article
• Language: English
• Subjects: Alloys; Applied sciences; Characterization and Evaluation of Materials; Chemistry and Materials Science; Coal-fired power plants; Corrosion resistance; Exact sciences and technology; Ferritic stainless steel; Mass spectrometry; Materials Science; Measurement techniques; Metallic Materials; Metallurgy; Metals. Metallurgy; Molybdenum; Nanotechnology; Pressure vessels; Structural Materials; Surfaces and Interfaces; Thin Films
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-010-0194-6

Carbide precipitation from the steel matrix during long-term high-temperature exposure can adversely affect the fracture toughness and high-temperature creep resistance of materials with implications on the performance of power plant components. In the present work, carbide evolution in 2.25Cr-1Mo steel after long-term aging during service was investigated. Boiler pipe samples of this steel were removed from a supercritical water-cooled coal-fired power plant after service times of 17 and 28 years and a mean operational temperature of 810 K (537 °C). The carbide precipitation and coarsening effects were studied using the carbon extraction replica technique followed by analysis using transmission electron microscopy and energy dispersive X-ray spectroscopy. The carbides extracted using an electrolytic technique were also analyzed using X-ray diffraction to evaluate phase transformations of the carbides during long-term service. Small ball punch and Vickers hardness were used to evaluate the changes in mechanical performance after long-term aging during service.