Microstructure after Solution Annealing of the Nuclear Grade Austenitic Stainless Steel DIN 1.4970

Abstract:

The main objective of the present work was to characterize the phases that are present after solution annealing in the microstructure of the titanium stabilized austenitic stainless steel W.-Nr. 1.4970, developed as a candidate material for fast breeder reactor fuel cladding. The crystalline structure, chemical composition, quantity, size, morphology, and distribution of the phases present in the microstructure after solution annealing heat treatments were studied in detail with the help of several complementary techniques. Chemical dissolution of the matrix has been performed using the Berzelius solution and the extracted residue has been analyzed by X-ray diffraction in a high precision camera. Three phases have been observed and identified after solution annealing heat treatments performed in the 1090 to 1300 °C temperature range, namely: (Ti,Mo)C; Ti (N,C) and Ti₄C₂S₂. The Ti-nitride and the Ti-carbosulfide did not dissolve in the steel matrix up to 1300 °C, on the other hand, the solubility of the (Ti,Mo)C raised strongly with temperature. A solution annealing heat treatment is recommended for the W. Nr. 1.4970 stainless steel.

• Periodical: Materials Science Forum (Volume 1016)
• Pages: 1147-1152
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.1016.1147
• Online since: January 2021
• Authors: Ronald Lesley Plaut*, Angelo Fernando Padilha, Flavio Beneduce Neto, Leandro Gomes de Carvalho
• Keywords: Austenitic Stainless Steel, Solution Annealing, Titanium Carbide, Titanium Carbosulfide, Titanium Nitride

References

[1] N. Cautaerts et al., J. Nucl. Mater., Thermal creep properties of Ti-stabilized DIN 1.4970 (15-15Ti) austenitic stainless steel pressurized cladding tubes, 493 (2017) 154-167.

DOI: 10.1016/j.jnucmat.2017.06.013

[2] A.F. Padilha, G. Schanz, K. Anderko, J. Nucl. Mater., Ausscheidungsverhalten des titanstabilisierten austenitischen stahls 15% Cr-15% Ni-1% Mo-Ti-B (DIN-Werkstoff-nr. 1.4970), 105 (1982) 77-92.

DOI: 10.1016/0022-3115(82)90454-8

[3] A.F. Padilha, P.R. Rios, ISIJ Int., Decomposition of austenite in austenitic stainless steels,42 (2002) 325-337.

DOI: 10.2355/isijinternational.42.325

[4] K.E. Burke, Metallogr., Chemical extraction of refractory inclusions from iron- and nickel-base alloys, 8 (1975) 473-488.

DOI: 10.1016/0026-0800(75)90023-3

[5] E.G. Hofmann, H. Jagodzinski, Z. Metallkd., A new high-resolution X-ray diffraction device with an improved focusing monochromator and X-ray tube (in German), 46 (1955) 601-610.

[6] E. Hellner, Z. Kristallogr., Intensity measurements performed on Guinier-camera films (in German), 106 (1954) 122-145.

[7] C. Da Casa, V.B. Nileshwar, J. Iron Steel Inst., Metallography of Y-phase in type 321 stainless steels, 207 (1969) 1003-1009.

[8] P. Duwez, F. Odell, J. Electrochem. Soc., Phase relationship in the binary systems of nitrides and carbides of zirconium, columbium, titanium and vanadium, 97 (1950) 299-304.

DOI: 10.1149/1.2777885

[9] V.N. Eremenko, T.Y. Velikanova, Sov. Powder Metall. Met. Ceram., The interaction of molybdenum with titanium carbide, 13 (1963) 347-352.

DOI: 10.1007/bf01194667

[10] M.L. Flem et al,J. Nucl. Mater., Microstructure and thermal conductivity of Mo-TiC cermets processed by hot isostatic pressing, 380 (2008) 85-92.

DOI: 10.1016/j.jnucmat.2008.01.033

[11] N. Cautaerts, et al., Acta Mater., Characterization of (Ti,Mo,Cr)C nanoprecipitates in an austenitic stainless steel on the atomic scale, 164 (2019) 90-98.

DOI: 10.1016/j.actamat.2018.10.018

[12] B.D. Cullity, Elements of X-ray diffraction, 2nd ed., Addison-Wesley, Reading, USA, (1978).

[13] A.N. Christensen, Acta Chem. Scand. A, The temperature factor parameters of some transition metal carbides and nitrides by single crystal X-ray and neutron diffraction, 32 (1978) 89-90.

DOI: 10.3891/acta.chem.scand.32a-0089

[14] J.F. Brown, W.D. Clark, B.A. Parker, Metallurgia (Manchester), The extraction of minor phases from austenitic steel, 56 (1957) 215-233.

[15] K. Wetzlar, G. Lennartz, DEW- Techn. Ber., On the occurrence of the titaniumsulphide Ti2S in titanium stabilized austenitic Cr-Ni steels (in German),1 (1961) 15-16.

[16] H. Kudielka, H. Rohde, Z. Kristallogr., Structural investigations of the carbosulfides of titanium and zirconium (in German), 114 (1960) 441-456.

[17] A.F. Padilha, J.C. Dutra, V. Randle, Mater. Sci. and Tech-Lond., Interaction between precipitation, normal grain growth, and secondary recrystallisation in austenitic stainless steel containing particles, 15 (1999) 1009-1014.

DOI: 10.1179/026708399101506850

[18] M. Deighton, J. Iron Steel Inst., Solubility of M23C6 in type 316 stainless steel, 208 (1970) 1012-1014.