Insight to the Microstructure Characterization of a HP Austenitic Heat Resistant Steel after Long-term Service Exposure

Mahyar Mohammadnejad, Vahid Javaheri, Morteza Shamanian, Shahram Rizaneh, Jerzy A Szpunar


Heat-resistant steels of HP series (Fe-25Cr-35Ni) are used in high temperature structural applications. Their composition include Nb as strong carbide former. Electron Backscatter Diffraction (EBSD) investigations revealed that, in the as-cast condition, alloys exhibit austenitic matrix with intergranular primary carbides such as MC, M23C6 and/or M7C3. During exposure at a high temperature, phase transformations occurred: chromium carbides of M7C3 type transform into the more stable M23C6 type, intergranular M23C6 carbides precipitate, and Lave phase due to increase of Niobium activity with temperature increase, as thermodynamic simulation confirmed. Therefore, combination of EBSD-EDS technique with thermodynamic calculation is one of the novel and most accurate method to investigation of phase transformation, as the precipitations are identified on the basis of their crystal structure, chemical composition and their thermodynamic features. 


Austenitic heat resistant steels, chromium carbide, Laves phase, EBSD, thermodynamic simulation

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M. Mostafaei, M. Shamanian, H. Purmohamad, M. Amini, A. Saatchi,” Microstructural degradation of two cast heat resistant reformer tubes after long term service exposure”, Engineering Failure Analysis 18 (2011) 164–171

A. Koblischka-Veneva, M.R. Koblischka, F. Mucklich,” Advanced microstructural analysis of ferrite materials by means of electron backscatter diffraction (EBSD)”, Journal of Magnetism and Magnetic Materials 322 (2010) 1178–1181

J. Liu, D. Jiao, Ch. Luo, “Microstructural evolution in austenitic heat-resistant cast steel 35Cr25Ni12NNbRE during long-term service”, Materials Science and Engineering A 527 (2010) 2772–2779

V. Javaheri, F. Shahri, M. Mohammadnezhad, M. Tamizifar, M. Naseri, “The effect of Nb and Ti on structure and mechanical properties of 12Ni-25Cr-0.4C austenitic heat-resistant steel after aging at 900oC for 1000h”, Journal of Material Engineering and Performance 23 (2014) 3558-3566

B. Sonderegger, S. Mitsche, H. Cerjak, “Microstructural analysis on a creep resistant martensitic 9–12% Cr steel using the EBSD method”, Materials Science and Engineering A 481–482 (2008) 466–470 Almeida, A.F. Ribeiro, I.L. May,” Microstructural characterization of modified 25Cr–35Ni centrifugally cast steel furnace tubes”, Materials Characterization 49 (2003) 219– 229

P. Hilkhuijsen, H.J.M. Geijselaers, T.C. Bor, “The influence of austenite texture on the martensitic transformation of an austenitic stainless steel”, Journal of Alloys and Compounds 577 (2013) 609–613

J.Laigo, F.Tancret, R.L.Gall, J.Furtado,” EBSD Phase Identification and Modeling of Precipitate Formation in HP Alloys”, Advanced Materials Research 15-17 (2007) 702-707

Aydin I, Buehler H-E, Rahmel A. Precipitation in the heat resistant nickel-base cast alloys G-NiCr 28 W and G-NiCr 50 Nb. Arch Eisenhuettenwes 54(1983) 461–466

Erdos E, X-ray diffraction. In: Van der Biest O, editor, “Analysis of high temperature materials”, New York, Applied Science Publisher; 1983. p. 203–205.

S.Y. Kondrat’ev, V.S. Kraposhin, G.P. Anastasiadi, A.L. Talis, “Experimental observation and crystallographic description of M7C3 carbide transformation in Fe–Cr–Ni–C HP type alloy”, Acta Materialia 100 (2015) 275-281

B. Sonderegger, S. Mitsche, H. Cerjak, “Martensite laths in creep resistant martensitic 9–12% Cr steels Calculation and measurement of misorientations”, Materials Characterization 58 (2007) 874–882

B. Ravi Kumar, A.K. Singh, B. Mahato, P.K. De, N.R. Bandyopadhyay, D.K. Bhattachary,” Deformation-induced transformation textures in metastable austenitic stainless steel”, Materials Science and Engineering A 429 (2006) 205–211

B. Peng, H. Zhang, J. Hong, J. Gao, H. Zhang, Q. Wang, J. Li, “The effect of M23C6 on the high-temperature tensile strength of two austenitic heat-resistant steels: 22Cr–25Ni–Mo–Nb–N and 25Cr–20Ni–Nb–N”, Materials Science and Engineering A 528 (2011) 3625–3629

N. Nabiran, S. Klein, S. Weber, W. Theisen,” Evolution of the Laves Phase in Ferritic Heat-Resistant Steels during Long-term Annealing and its Influence on the High-Temperature Strength”, Metallurgical and Materials Transaction A 46A (2015) 102-114

J. Froitzheim, G.H. Meier, L. Niewolak, P.J. Ennis, H. Hattendorf, L. Singheiser, W.J. Quadakkers, “Development of high strength ferritic steel for interconnect application in SOFCs”, Journal of Power Sources 178 (2008) 163–173

S.W. Chen, C. Zhang, Z.X. Xia, H. Ishikawa, Z.G. Yang, “Precipitation behavior of Fe2Nb Laves phase on grain boundaries in austenitic heat resistant steels”, Materials Science & Engineering A 616 (2014)183–188



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