Microstructural analysis of a HP 40Nb alloy aged

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Milica Timotijević
Olivera Erić Cekić
Dragan Rajnović
Petar Janatović


In this paper, the change in the microstructure of the centrifugally cast heat-resistant alloys of HP40 Nb after exposure to 0.5h and 2h of ageing times at 1123K and 1323K were investigated. The microstructures of the as-received alloy and aged conditions were examined using light microscopy (LM) and scanning electron microscopy (SEM) equipped with an energy dispersive spectroscopy (EDS). The chemical composition of various phases and precipitates observed in the aged sample microstructure was characterized by the means of scanning electron microscopy SEM via back-scattered electron (BSE). The present results indicate that ageing enhanced the occurrence of different phenomena such as the transformation of primary M7C3 to M23C6 carbides and precipitation of secondary M23C6 carbides. It can be summarized that the present phases and the morphology of secondary carbides in the microstructure of aging results in higher values of hardness.

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D.J. Tillack and J.E. Guthrie, “Wrought and Cast Heat-Resistant Stainless Steels and Nickel Alloys for the Refining and Petrochemical Industries”, Nickel Development Institute, Technical Series No. 10071, (1998)

D.B. Roach and J.A. Van Echo, “Comparison of the Properties of the HK-40 and HP-45 Cast Heat-Resistant Alloys. Stainless Steel Castings, ASTM STP, Vol. 756, pp. 275-312. http://dx.doi.org/10.1520/STP28447S, (1982)

W.T. Hou and R.W.K. Honeycombe, “Structure of Centrifugally Cast Austenitic Stainless Steels: Part 1 HK 40 as Cast and after Creep between 750˚C and 1000˚C”, Materials Science and Technology, Vol. 1, pp. 385-389. http://dx.doi.org/10.1179/mst.1985.1.5.385, (1985)

R.A.P. Ibañez, L.H. de Almeida, and I. Le May, “Effects of Si Content on the Microstructure of Modified-HP Austenitic Steels”, Materials Characterization, Vol. 30, pp. 243-249. http://dx.doi.org/10.1016/1044-5803(93)90071-3, (1993)

Blair, M.C. “Cast Stainless Steels”, Metals Handbook, 1, ASM (USA), (1982)

J. Rodríguez, S. Haro, A. Velasco, and R. Colás, “A Metallographic Study of Aging in Cast-Heat Resisting Alloy”, Materials Characterization, Vol. 45, pp. 25-32, http://dx.doi.org/10.1016/S1044-5803(00)00047-4, (2000)

L.H. de Almeida, A. F. Ribeiro, and I. Le May, “Microstructural Characterization of Modified 25Cr-35Ni Centrifugally Cast Steel Furnace Tubes”, Materials Characterization, Vol. 49, pp. 219-229, http://dx.doi.org/10.1016/S1044-5803(03)00013-5, (2003)

R. Voicu, E. Andrieu, D. Poquillon, J. Furtado and J. Lacaze, “Microstructure Evolution of HP40-Nb Alloys during Aging Under Air at 1000˚C”, Materials Characterization, Vol. 60, pp. 1020-1027, https://doi.org/10.1016/j.matchar.2009.04.007, (2009)

C.J. Liu and Y. Chen, “Variations of the microstructure and mechanical properties of HP40Nb hydrogen reformer tube with time at elevated temperature”, Materials & Design, Vol. 32, pp. 2507–2512, https://doi.org/10.1016/j.matchar.2008.02.001, (2011)

T. Dessolier, T. McAuliffe, W. J. Hamer, C. G.M. Hermse and T. B. Britton, “Effect of high temperature service on the complex through-wall microstructure of centrifugally cast HP40 reformer tube”, Materials Characterization, Vol.177, p. 111070, https://doi.org/10.1016/j.matchar.2021.111070, (2021)

C-M. Fuyang, J-Y. Chen, B. Shao, Y. Zhou, J-M.Gong, X-F. Guo and Y. Jiang, “Effect of microstructural evolution in thermal exposure on mechanical properties of HP40Nb alloy”, International Journal of Pressure Vessels and Piping, International Journal of Pressure Vessels and Piping, Vol.192, p. 104391, https://doi.org/10.1016/j.ijpvp.2021.104391, (2021)

A.F. Padilha, I.F. Machado, and R.L. Plaut, “Microstructures and Mechanical Properties of Fe-15%Cr-15%Ni Austenitic Stainless Steels Containing Different Level of Niobium Addition Submitted to Various Processing Stages”, J. Mater. Process. Technol., Vol.170, pp. 89–96, https://doi.org/10.1016/j.jmatprotec.2005.05.002 , (2005)

J. Laigo, F. Tancret, R. Le Gall and J. Furtado, “EBSD phase identification and modeling of precipitate formation in HP alloys”, Vol. 15-17, pp. 702-707, Advance Materials Research, https://doi.org/10.4028/www.scientific.net/AMR.15-17.702, (2007)

I. A. Sustaita–Torres, S. Haro-Rodríguez , M. P. Guerrero-Mata, M. de la Garza, E. Valdés, F. Deschaux-Beaume and R. Colás, “Aging of a cast 35Cr–45Ni heat resistant alloy”, Materials Chemistry and Physics, Vol. 133, pp. 1018-1023, https://doi.org/10.1016/j.matchemphys.2012.02.010, (2012)

A. Carlos Picasso, C. Armando L. Matías S. Lissarrague, A. Daniel Garófoli, “Microstructure Evolution of a Nickel-Base Alloy Resistant to High Temperature during Aging”, Journal of Minerals and Materials Characterization and Engineering, Vol.4, pp.48-61 (2016), http://dx.doi.org/10.4236/jmmce.2016.41006

I. Le May, T.L. Silveira and C.H. Vianna, “Criteria for the evaluation of damage and remaining life in reformer furnace tubes”, Int. J.Press. Vessels Pip. Vol. 66, pp. 233-241, https://doi.org/10.1016/0308-0161(95)00098-4, (1996)

G.D. De Almeida Soares, L.H. De Almeida, T.L. Da Silveira and I. Le May, “Niobium additions in HP heat-resistant cast stainless steels”, Mater Characterization, Vol. 29, pp. 387–396, https://doi.org/10.1016/1044-5803(92)90045-J, (1992)

J. Laigo F. Christien, R. Le Gall, F. Tancret and J. Furtado, “SEM, EDS, EPMA-WDS and EBSD characterization of carbides in HP type heat resistant alloys”, Materials characterization, Vol.59, pp. 1580-1586, https://doi.org/10.1016/j.matchar.2008.02.001, (2008)

T. Sourmail, “Precipitation in creep resistant austenitic stainless steels”, Mater Sci Technol, Vol. 17, pp. 1–14, https://doi.org/10.1179/026708301101508972, (2001)