Toughness-drop in AISI 316L pipe after service
exposure at 720 °C for 100,700 hours

Flavio Pereira de Moraes; Emanuelle Machado Amaral; Flávio Beneduce Neto; Angelo Fernando Padilha

doi:10.4322/2176-1523.20243080

Artigo Original

Toughness-drop in AISI 316L pipe after service exposure at 720 °C for 100,700 hours

Queda de tenacidade em tubulação de AISI 316L após exposição em serviço a 720 °C por 100.700 horas

Flavio Pereira de Moraes; Emanuelle Machado Amaral; Flávio Beneduce Neto; Angelo Fernando Padilha

http://dx.doi.org/10.4322/2176-1523.20243080 Tecnol. Metal. Mater. Min., vol.21, e3080, 2024

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Abstract

AISI 316L austenitic stainless steel pipes employed in a petrochemical industry for 100,700 hours at 720 °C were examined in this study. During this exposure, the microstructure changed significantly, and the toughness of the pipe decreased dramatically. Detailed microstructural analyses revealed that although several phases precipitated during service, sigma phase precipitation at the grain boundaries was primarily responsible for the observed decrease in toughness. Nonetheless, the decreased toughness did not hinder the operation of the pipes until the anticipated deadline of the project.

Keywords

AISI 316L; Pipes; Sigma phase; Toughness-drop

Resumo

Tubulação de aço inoxidável austenítico AISI 316L foi utilizada em uma indústria petroquímica por 100.700 horas a 720 °C. Durante esta exposição, a microestrutura do aço mudou significativamente e a tenacidade dos tubos caiu drasticamente. As análises realizadas neste trabalho mostraram que, embora diversas fases tenham precipitado durante a operação, a precipitação da fase sigma nos contornos de grão foi a principal responsável pela queda de tenacidade. Contudo, vale ressaltar que a queda de tenacidade não impediu que as tubulações continuassem normalmente em operação até o prazo limite previsto no projeto.

Palavras-chave

AISI 316L; Tubulação; Fase sigma; Queda de tenacidade

Referências

1 Plaut RL, Herrera C, Escriba DM, Rios PR, Padilha AF. A short review on wrought austenitic stainless steels at high temperatures: processing, microstructure, properties and performance. Materials Research. 2007;10:453-460. http:// doi.org/10.1590/S1516-14392007000400021.

2 Qin W, Li J, Liu Y, Kang J, Zhu L, Shu D, et al. Effects of grain size on tensile property and fracture morphology of 316L stainless steel. Materials Letters. 2019;254:116-119. http://doi.org/10.1016/j.matlet.2019.07.058.

3 Davis JR. ASM Specialty Handbook: Stainless Steels. Ohio: ASM International; 1994.

4 Moraes FP, Amaral EM, Neto FB, Padilha AF. Failure analysis of an AISI 316 steel pipe elbow exposed to the weather for three years after 16 years of operating at 515 °C. Tecnologica em Metalurgia, Materiais e Mineração. 2023;20:e2879. http://doi.org/10.4322/2176-1523.20232879.

5 Chopra OK. Effects of thermal aging and neutron irradiation on crack growth rate and fracture toughness of cast stainless steels and austenitic stainless steel welds. NUREG/CR-7185. ANL-14/10. USA: Nuclear Regulatory Commission, 2015.

6 Was GS. Fundamentals of radiation materials science. 2nd ed. Berlin/Heidelberg: Springer-Verlag GmbH; 2017. Chapter 14: Fracture and Embrittlement. pp. 793-856.

7 Griffiths M. Effect of neutron irradiation on the mechanical properties, swelling and creep of austenitic stainless steels. Materials (Basel). 2021;14(10):2622. http://doi.org/10.3390/ma14102622.

8 Weiss B, Stickler R. Phase instabilities during high temperature exposure of 316 austenitic stainless steel. Metallurgical and Materials Transactions. B, Process Metallurgy and Materials Processing Science. 1972;3:851-866.

9 Weiss B, Hughes CW, Stickler R. SEM-Techniques for microcharacterization of metals and alloys II. Practical Metallography. 1971;8(9):528-542.

10 Lai JKL. A study of precipitation in AISI type 316 stainless steel. Materials Science and Engineering. 1983;58(2):195-209. http://doi.org/10.1016/0025-5416(83)90046-0.

11 Minami Y, Kimura H, Ihara Y. Microstructural changes in austenitic stainless steels during long-term aging. Materials Science and Technology. 1986;2(8):795-806. http://doi.org/10.1179/mst.1986.2.8.795.

12 Padilha AF, Rios PR. Decomposition of austenite in austenitic stainless steel. ISIJ International. 2002;42(4):325- 327. http://doi.org/10.2355/isijinternational.42.325.

13 Padilha AF, Escriba DM, Materna-Morris E, Rieth M, Klimenkov M. Precipitation in AISI 316L(N) during creep tests at 550 and 600 °C up to 10 years. Journal of Nuclear Materials. 2007;362:132-138. http://doi.org/10.1016/j. jnucmat.2006.12.027.

14 Moraes FP, Alves SF Jr, Plaut RL, Padilha AF. Degradation of microstructure and properties of an AISI 316L steel pipe after more than 100,000 hours usage at 640 °C in a petrochemical industry. Procedia Structural Integrity. 2019;17:131-137. http://doi.org/10.1016/j.prostr.2019.08.018.

15 National Institute of Materials Science. Creep data sheet: metallographic atlas of long-term crept materials, no. M-2: micrographs and microstructural characteristics of crept specimens of 18Cr-12Ni-Mo stainless steel for boiler and heat exchanger seamless tubes (SUS 316H TB). Japan: NIMS; 2003.

16 Sourmail T. Precipitation in creep resistant austenitic stainless steels. Materials Science and Technology. 2001;17:1-14. http://doi.org/10.1179/026708301101508972.

17 Rios PR, Padilha AF. Precipitation from austenite. In: Hashmi S, editor, Reference module in materials science and materials engineering. Oxford: Elsevier; 2019. pp. 1-8.

18 Johansson C, Lind M. Evaluation of the η (Eta) nitride with three laboratory melts [thesis]. Stockholm, Sweden: KTH; 2015.

19 Maziasz PJ. The formation of diamond-cubic eta phase in type 316 stainless steel exposed to thermal aging or irradiation environments. Scripta Metallurgica. 1979;13:621-626. http://doi.org/10.1016/0036-9748(79)90121-2.

20 Martorano MA, Tavares CF, Padilha AF. Predicting delta ferrite content in stainless steel castings. ISIJ International. 2012;52(6):1054-1065. http://doi.org/10.2355/isijinternational.52.1054.

21 Santos FAM, Martorano MA, Padilha AF. Delta ferrite formation and evolution during slab processing from an 80-ton industrial heat of AISI 304 austenitic stainless steel. REM - International Engineering Journal. 2023;76(1):47- 54. http://doi.org/10.1590/0370-44672022760001.

22 Benes L. Correlation between chemical compositions and ferrite contents of austenitic stainless steels. MetalurgiaBucharest. 1978;30(8):467-469.

23 Neidel A, Fischer B, Rienbeck S, Cagliyan E. Transformation of delta ferrite into sigma-phase in metastable austenitic stainless steels after long-term high-temperature service exposure. Practical Metallography. 2014;51(4):259-279. http://doi.org/10.3139/147.110278.

24 Wang Q, Chen S, Rong L. δ-Ferrite formation and its effect on the mechanical properties of heavy-section AISI 316 stainless steel. Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science. 2020;51A:2998-3008. http://doi.org/10.1007/s11661-020-05717-0.

25 Petzow G. Metallographic etching. Metals Park, Ohio, USA: American Society for Metals; 1978.

Submetido em:
09/02/2024

Aceito em:
07/07/2024