Microstructure Characterization for P92 Steels Subjected to Short Term Overheating above Critical Transformation Temperatures

Abstract:

Advanced ferritic steels containing 9 wt% Cr are widely used for nuclear and fossil energy applications, especially in the construction of supercritical and ultra supercritical boiler components. The microstructure of the as supplied 92 materials consists of a tempered martensite matrix, a fine dispersion of intergranular chromium rich M₂₃C₆ precipitates and intragranular carbonitrides MX particles rich in V and Nb. This steel requires post weld heat treatment (PWHT) to produce a tempered microstructure after welding to develop excellent creep strength for high temperature service. The short excursion to high temperature beyond Ac₁ and Ac₃ would have resulted in the formation of deleterious phases, for example, soft α-ferrite which has a poor creep strength and hard martensite which has a low toughness. In this study, the microstructure evolution as a result of short exposure to various peak temperatures above Ac₁ and Ac₃ is analyzed. Creep rupture database for overheated condition will be established after the completion of uninterrupted creep testing.

• Periodical: Applied Mechanics and Materials (Volume 625)
• Pages: 114-117
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.625.114
• Online since: September 2014
• Authors: Ng Guat Peng*, Badrol Ahmad, Mohd Razali Muhamad, Mohd Ahadlin
• Keywords: Ac₁, Ac₃, Martensitic, Microstructure, PWHT

References

[1] V.K. Sikka and P. Patriarca. Technical report, Metals and Ceramics Division. Oak Ridge National Laboratory, USA. (1984). Pp 101-116.

[2] K. Iwanaga, T. Tsuchiyama and S. Takaki. Key Engineering Material, 171-174 (2000). pp.477-482.

[3] Nippon Steel Corporation, Data Package for NF616 Ferritic Steel, January 1993, second edition, March (1994).

[4] A. Czyrska-Filemonowicz, A. Zielinska_Lipiec, P.J. Ennis. Modified 9% Cr Steels for advanced power generation: microstructure and properties. Journal of achievements in materials and manufacturing engineering, Vol 19, Issue 2, Dec (2006).

[5] R.C. MacLachlan, J.J. Sanchez-Hanton and R.C. Thomson. The effect of simulated post weld heat treatment temperature overshoot on micro structural evolution in P91 and P92 power plant steels. Proceedings from the sixth international conference on Advances In Materials Technology for Fossil Power Plants. August 31-September 3, 2010, Sante Fe, New Mexico, USA. Copyright @2011 Electric Power Research Institute, distributed by ASM International. pp.787-799.

[6] B.K. Choudhary, E. Issac Samuel. Creep Behavior of Modified 9Cr-1Mo Ferritic Steel. Journal of Nuclear Materials. 412 (2011). Pp 82-89.

DOI: 10.1016/j.jnucmat.2011.02.024