Microstructural Degradation of Super304H after Long-Term Service Exposure

Abstract:

Super304H is austenitic steel used predominantly for boiler and turbine components in thermal power plants due to the high strength, excellent creep and oxidation resistance in high-temperature steam environments. Microstructural degradation is inevitable upon long-term high-temperature exposure. Therefore, understanding the processes of degradation is critical for the determination of residual lifetime of the parts. In this study, the hardness, tensile strength and creep strength of a Super304H steel that was in service as a reheater for ~8 years at about 600°C was investigated with corresponding microstructural analysis. Grain growth is evident, but microhardness and tensile strength did not decrease, due to the precipitation of nanosized NbX and Cu-rich particles in grain interior. However, the creep rupture life of the aged S304H steel is ~90% lower at 650°C than that of the virgin S304H, due to the coarsening of σ phase and formation of M₂₃C₆ on the grain boundary. Our measurements and analysis of the specimens in this study indicates the remaining service life longer than those in the NIMS database.

• Periodical: Defect and Diffusion Forum (Volume 439)
• Pages: 209-219
• DOI: https://doi.org/10.4028/p-3fORpV
• Online since: February 2025
• Authors: Li Ming Xu, Yin Sheng He, Keesam Shin*
• Keywords: Creep, Long-Term Exposure, Microstructural Degradation, Super304H

References

[1] Iseda A, Okada H, Semba H, Igarashi, M. Long term creep properties and microstructure of SUPER304H, TP347HFG and HR3C for A-USC boilers. Energy Mater 2007; 2:199–206

DOI: 10.1179/174892408X382860

[2] Paper: Viswanathan R, Robert Purgert. US program on materials technology for ultra-supercritical coal-fired steam power plants. In: ASME Pressure Vessels and Piping Conference 2007, Vol. 42878

DOI: 10.1361/10599490524039

[3] Yoo K.B, He Y.S, Lee H.S, Bae S.Y, Kim D.S. Study on the microstructural degradation of the boiler tubes for coal-fired power plants. KEPCO Journal on Electric Power and Energy 2018; 4(1): 25-31

[4] Lee H.S, Jung J.S, Kim D.S, Yoo K.B. Failure analysis on welded joints of 347H austenitic boiler tubes. Engineering Failure Analysis 2015; 57: 413-422

DOI: 10.1016/j.engfailanal.2015.08.024

[5] Zheng, Z, Zhang, J, Sun, X, Zhang, J, He, H, Lu, X. Failure analysis of the TP347H austenitic stainless steel tube of boiler reheater in a coal-fired power plant. Engineering Failure Analysis 2021; 121:105154

DOI: 10.1016/j.engfailanal.2020.105154

[6] Morris Jr, J.W, The influence of grain size on the mechanical properties of steel. 2001, [Internet]. Available from: https://www.osti.gov/servlets/purl/861397

[7] Anwar M.S, Widjaya R.R, Prasetya L.B.A, Arfi A.A, Mabruri E, Siradj E.S. Effect of Grain Size on Mechanical and Creep Rupture Properties of 253 MA Austenitic Stainless Steel. Metals 2022; 12(5): 820

DOI: 10.3390/met12050820

[8] Naghizadeh M, Mirzadeh H. Effects of grain size on mechanical properties and work-hardening behavior of AISI 304 austenitic stainless steel. Steel research international 2019 90(10): 1900153

DOI: 10.1002/srin.201900153

[9] R.P. de Siqueira, J.F.S. Feiteira, D.J.R. da Costa, J. Fabrício, C. Lins. Investigation of the Grain Growth Evolution in the AISI 304H Austenitic Stainless Steel. Journal of Mechanics Engineering and Automation 2016; (6):95-99

DOI: 10.17265/2159-5275/2016.02.005

[10] Sun G, Zhao M, Du L, Wu, H. Significant effects of grain size on mechanical response characteristics and deformation mechanisms of metastable austenitic stainless steel. Materials Characterization 2022; 184:111674

DOI: 10.1016/j.matchar.2021.111674

[11] Jin X, Xia X, Li Y, Zhao Y, Xue F, Zhang G. Quantitative study of microstructure evolution and the effect on mechanical properties of Super304H during aging. Materials at High Temperatures 2019; 36(5):459-470

DOI: 10.1080/09603409.2019.1632508

[12] Zieliński A, Wersta R, Sroka M. The study of the evolution of the microstructure and creep properties of Super 304H austenitic stainless steel after aging for up to 50,000 h. Archives of Civil and Mechanical Engineering 2022;22(2):1-24

DOI: 10.1007/s43452-022-00408-6

[13] Shanthi G, Nanibabu M, Krishnan S.A, Moitra A, Vasudevan, M. Effect of Thermal Aging on Deformation and Fracture Properties of SS 304HCu. Journal of Materials Engineering and Performance 2022;12:1-10

DOI: 10.1007/s11665-022-07408-w

[14] Horváth J, Král P, Janovec J. The effect of σ-phase formation on long-term durability of welding joints in SUPER 304H steels. Acta Phys. Pol. A 2016;130:960-962

DOI: 10.12693/APhysPolA.130.960

[15] Zieliński A, Wersta R, Sroka M. Analysis of the precipitation process of secondary phases after long-term ageing of the S304H steel. Bulletin of the Polish Academy of Sciences. Technical Sciences 2021;69(5)

DOI: 10.24425/bpasts.2021.137520

[16] Paper: MURATA M, TANAKA H, ABE F, IRIE H. Assessment of Material Degradation Based on Microstructural Evolution in Type 304H Stainless Steel During Long-Term Creep (Changes in Microstructure 2). In Creep: proceedings of the... international conference on creep and fatigue at elevated temperatures 2001;1:383-387. http://dl.ndl.go.jp/info:ndljp/pid/10351952

DOI: 10.1016/s0921-5093(01)01012-7

[17] Pulsford C, J, et al. Microstructural characterization of creep tested advanced austenitic stainless steel super 304H. Materials at High Temperatures 2022;39:416-426

DOI: 10.1080/09603409.2022.2037328

[18] ASTM A213/A213M-06a. Standard Specification for Seamless Ferritic and Austenitic Alloy-Steel Boiler, Superheater and Heat-Exchangers Tubes, 2006 [Internet]. Available from: https://www.astm.org/a0213_a0213m-18.html

DOI: 10.1520/a0213_a0213m-09b

[19] ASTM E139-11. Standard Test Methods for Conducting Creep, Creep-Rupture, and Stress-Rupture Tests of Metallic Materials, 2018 [Internet]. Available from: https://www.astm.org/e0139-11r18.html

DOI: 10.1520/e0139-00e01

[20] Tamura M, Abe F, Shiba K, Sakasegawa H, Tanigawa, H. Larson–Miller constant of heat-resistant steel. Metallurgical and materials transactions A 2013; 44(6): 2645-2661

DOI: 10.1007/s11661-013-1631-0

[21] Sourabh K, Singh JB. Creep behavior of alloy 690 in the temperature range 800–1000°C. Journal of Materials Research and Technology 2022;17:1553-69

DOI: 10.1016/j.jmrt.2022.01.060

[22] Sawada K, Hatakeyama T, Sekido K, Kimura K. Microstructural changes and creep-strength degradation in 18Cr-9Ni-3Cu-Nb-N steel. Materials Characterization 2021;178:111286

DOI: 10.1016/j.matchar.2021.111286

[23] Loghman A, Moradi M. Creep damage and life assessment of thick-walled spherical reactor using Larson–Miller parameter. International Journal of Pressure Vessels and Piping 2017;1(151):11-9

DOI: 10.1016/j.ijpvp.2017.02.003

[24] NIMS Creep data sheet No.56A. Data sheets on the elevated-temperature properties of 18Cr-9Ni-3Cu-Nb-N stainless steel tubes for power boilers (KA-SUS 304J1 HTB) 2018. https://smds.nims.go.jp/MSDS/ja/sheet/Creep.html#4

[25] ASTM E112-13. Standard test methods for determining average grain size, 2021 [Internet]. Available from: https://www.astm.org/e0112-13r21.html

[26] Hong H.U, Rho, B.S, Nam, S.W. Correlation of the M23C6 precipitation morphology with grain boundary characteristics in austenitic stainless steel, Mater. Sci. Eng. A 2001;318:285–292

DOI: 10.1016/S0921-5093(01)01254-0

[27] Alsmadi Z.Y, Abouelella H, Alomari A.S, Murty K.L. Stress-controlled creep–fatigue of an advanced austenitic stainless steel at elevated temperatures. Materials 2022; 15:3984

DOI: 10.3390/ma15113984

[28] Bai J.W, et al. Coherent precipitation of copper in Super304H austenite steel, Materials science and engineering A 2013;584:57-62

DOI: 10.1016/j.msea.2013.06.082

[29] Chi C.Y, et al. The precipitation strengthening behavior of Cu-rich phase in Nb contained advanced Fe-Cr-Ni type austenitic heat resistant steel for USC power plant application, Progress in Nature Science: Materials International 2012;22(3):175-185

DOI: 10.1016/j.pnsc.2012.05.002