Stability of Microstructure and Mechanical Properties of GH984G Alloy during Long-Term Thermal Exposure

Abstract:

A low cost Ni-Fe-based wrought superalloy for 700 advance ultra-supercritical coal-fired power plants was developed. The stability of microstructure and mechanical properties of this alloy during long-term thermal exposure was investigated by SEM,TEM and tensile tests. The experimental results showed that the major precipitates in the alloy were spherical γ, MC and discrete M₂₃C₆ distributing along grain boundary after the long-term exposure at 700 and 750 and no harmful phases, such as σ phase and η phase, were found. However, after exposure at 800 up to 3000 h, small amount of lath-like η phase precipitated at grain boundary by consuming the surrounding γ. The η phase exhibited a fixed orientation relationship with the γ matrix. During thermal exposure γ coarsened with increasing the exposure time and exposure temperature. In addition, all major phases and their stability temperature ranges were calculated by JMatPro and these results were confirmed by the experimental results. The 700 tensile tests revealed that the alloy after exposure at 700 and 750 for 3000 h exhibited excellent ductility and strength. Therefore, the GH984G alloy possessed excellent stability of microstructure and mechanical properties between 700 and 750 up to 3000 h, and it is a promising material for 700 advance ultra-supercritical coal-fired power plants.

• Periodical: Materials Science Forum (Volumes 747-748)
• Pages: 647-653
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.747-748.647
• Online since: February 2013
• Authors: Ting Ting Wang, Chang Shuai Wang, Jian Ting Guo, Lan Zhang Zhou
• Keywords: Mechanical Property, Microstructural Stability, Ni-Fe-Based Wrought Superalloy, Precipitate, Thermal Exposure

References

[1] R. Viswanathan, W. Bakker, Materials for Ultrasupercritical Coal Power Plants-Boiler Materials, Part 1. J. Mater. Eng. Perf. 10 (2001) 81-95.

DOI: 10.1361/105994901770345394

[2] B. Jørgen, K. Sven, R. Blum, High-efficiency coal-fired power plants development and perspectives, Energy. 31 (2006) 1439-41.

[3] S.J. Patel, Introduction to Inconel alloy 740: an alloy designed for superheater tubing in coal-fired ultrasupercritical boilers, Acta. Metall. Sin. (English letter). 18 (2005) 479-88.

DOI: 10.7449/2005/superalloys_2005_601_611

[4] S.Q. Zhao, X.S. Xie, G.D. Smith, S.J. Patel, Microstructural stability and mechanical properties of a new nickelbased superalloy, Mater. Sci. Eng. A. 355 (2003) 96-105.

[5] R. Viswanathan, J. Sarver, J.M. Tanzosh, Boiler Materials for Ultra-Supercritical Coal Power Plants—Steamside Oxidation, Journal of Materials Engineering and Performance. 15 (2006) 255-274.

DOI: 10.1361/105994906x108756

[6] J.T. Guo, The current situation of application and development of superalloys in the fields of energy industy, Acta. Metall. Sin. (in Chinese). 46 (2010) 513-27.

[7] L.Y. Sheng, Y. Xie, T.F. Xi, J.T. Guo, Y.F. Zheng, H.Q. Ye. Microstructure characteristic and compressive properties of NiAl-based multiphase alloy during heat treatments. Mater. Sci. Eng. A 528 (2011) 8324-41.

DOI: 10.1016/j.msea.2011.07.072

[8] S.H. Wang, X.K. Du, J.T. Guo, Changes of carbides during long term aging in GH984 alloy, Acta. Metall. Sin. (in Chinese). 19 (1998) 36-41.

[9] J.T. Guo, X.K. Du, A superheater tube superalloy GH2984 with excellent properties, Acta Metall Sin (in Chinese). 41 (2005) 1221-27.

[10] Metallic materials - Tensile testing at elevated temperature (ISO 783: 1999, MOD), GB/T4338-2006. p.5.

[11] D. MUKHERJI, P. STRUNZ, D.D. GENOVESE, R. GILLES, J. RÖSLER, A, WIEDENMANN, Investigation of Microstructural Changes in INCONEL 706 at high Temperatures by In-Situ Small-Angle Neutron Scattering, Metall Mater Trans A. 34A (2003) 2781-92.

DOI: 10.1007/s11661-003-0179-9

[12] Y.U. Heo, M. Takeguchi, K. Furuya, C. Leeh, Transformation of DO24 g-Ni3Ti phase to face-centered cubic austenite during isothermal aging of an Fe–Ni–Ti alloy, Acta Mater. 57 (2009) 1176-1187.

DOI: 10.1016/j.actamat.2008.10.056

[13] L. Xu, C.Y. Cui, X.F. Sun, The effects of Co and Ti additions on microstructures and compressive strength of Udimet710, Mater Sci Eng A. 528 (2011) 7851-7856.

DOI: 10.1016/j.msea.2011.07.019

[14] I. M. Lifshitz, V.V. Slyozov. The kinetics of precipitation from supersaturated solid solution. J. Phys. Chem. Solids. 19 (1961) 35-50.

DOI: 10.1016/0022-3697(61)90054-3

[15] C. Wagner, Theorie der alterung von niederschlagen durch umlösen (Ostwald–Reifung), Z. Elektrochem. 65 (1961) 581-591.

DOI: 10.1002/bbpc.19610650704