Features of chemical composition and structural-phase state decreasing corrosion resistance of parts from 18Cr-10Ni steel

Features of the chemical composition and structural-phase state of samples of steel 18Cr-10Ni (AISI 304) were investigated, which could contribute to the occurrence of general corrosion damage and the pittings formation on parts made of this steel under the influence of an aggressive environment. It has been established that the sulfur content in steel is almost 10 times higher than the level established by the standard for this steel (0.03 % S), therefore, it contains about 3 vol. % of manganese sulfides, 1 – ~ 50 μm in size, forming stitches and accumulations along direction of rolling. According to the literature, it is the particles of manganese sulfide (MnS) that are most corrosive in corrosion-resistant steels and alloys. They significantly reduce the ability of Fe – Cr – Ni steels to passivate in a corrosive environment. For the formation of FeSH⁺ ions, a high concentration of S2– ions is required. The larger the inclusions of sulfide particles are, the higher is their ability to reduce the corrosion resistance of steel. Therefore, the large size of MnS particles found in steel plays an important negative role. It is shown that an additional factor contributing to a decrease in the corrosion resistance of the studied steel is the presence of deformation martensite in the surface layer of the steel, which was formed in the process of machining during manufacturing by cutting and grinding parts from a billet. The appearance of this martensite is due to the low concentration of austenite-forming elements (0.01 – 0.04 % C, 7.96 – 8.23 % Ni). The steel on the modified Scheffler-Delong diagram is in the region where martensite can form; the calculated value of М_d(30/50) for it was 28 °С. According to literature data, deformation martensite in steels of 18-10 type causes a decrease in their resistance to pitting corrosion in solutions of acids and salts. It is shown that the presence of an electric potential activates the corrosive effect on 18Cr-10Ni steel samples in an acidic environment. It is concluded that the corrosion damage of parts made of the studied steel was facilitated by the presence of accumulations of sulfide particles in individual areas of the metal, combined with the presence of deformation martensite in these areas.

1. Freiman L.I., Reformatskaya I.I., Markova T.P. Enhancement of steel corrosion resistance by prevention of manganese sulfide inclusions formation. Khimicheskoe i neftyanoe mashinostroenie. 1991, no. 10, pp. 576–580. (In Russ.).

2. Freiman L.I., Kolotyrkin Ya.M., Reformatskaya I.I., etc. Alloying effect of Mo in stainless steel enhanced by reducing S and Mn impurities. Zashchita metallov. 1992, vol. 28, no. 2, pp. 179–184. (In Russ.).

3. Reformatskaya I.I., Freiman L.I. Precipitation of sulfide inclusions in steel structure and their effect on local corrosion processes. Zashchita metallov. 2002, vol. 37, no. 5, pp. 511–516. (In Russ.).

4. Kolotyrkin Ya.M., Freiman L.I. Role of non-metallic inclusions in corrosion processes. In: Results of Science and Technology. Series: Corrosion and Corrosion Protection. Moscow: VINITI, 1978, vol. 6, pp. 5–52. (In Russ.).

5. Reformatskaya I.I. Influence of the structure defining factors on the corrosion-electrochemical behavior of iron and stainless steel. Russian Journal of General Chemistry. 2009, vol. 79, no. 9, pp. 1955–1964.

6. Pickering H.W., Frankenthal R.P. On the mechanism of localized corrosion of iron and stainless steel: I. Electrochemical Studies. Journal of the Electrochemical Society. 1972, vol. 119, no. 10, p. 1297–1310. https://doi.org/10.1149/1.2403982

7. Malinochka Ya.N. Changes in sulfides and properties of steel under high heating. In: TsNIIchermet Coll. of Sci. Papers. Steel and NonMetallic Inclusions. Moscow: Metallurgiya, 1980, pp. 66–78. (In Russ.).

8. Zav’yalov V.V. Problems of Operational Reliability of Pipelines at the Late Stage of Field Development. Moscow: OAO “VNIIOENG”, 2005, 322 p. (In Russ.).

9. Romashkin A.N. Effect of non-metallic inclusions on corrosion resistance of steel. [Electronic resource]. Available at URL: http:// steelcast.ru/corrosion_resestance (In Russ.).

10. Forchhammer P., Engell H.-J. Untersuchungen über den Lochfraß an passiven austenitischen Chrom-Nickel-Stählen in neutralen Chloridlösungen. Werkstoffe und Korrosion. 1969, vol. 20, no. 1, pp. 1–12. ( In Germ.).

11. Searson P.S., Latanision P.M. A comparison of the general and localized corrosion resistance of conventional and rapidly solidified AISI 303 stainless steel. Corrosion. 1967, vol. 42, no. 1, pp. 161–168.

12. Zaitsev A.I., Rodionova I.G., Mal’tsev V.V., etc. Nature and mechanisms of formation of corrosion-active non-metallic inclusions in steel. Ways to ensure the purity of steel for these inclusions. In: Corrosion-Active Non-Metallic Inclusions in Carbon and Low-Alloy Steels. Moscow: Metallurgizdat, 2005, pp. 37–51. (In Russ.).

13. Kovalev A., Veiss A., Sheler P.R., Vorob’ev K., Krisher M., Fridrikh Kh.E. Influence of isothermal α′-martensite on mechanical properties and corrosion resistance of high-alloy cast Cr–Mn–Ni steels. Vestnik permskogo gosudarstvennogo tekhnicheskogo universiteta. Mashinostroenie, materialovedenie. 2011, vol. 13, no. 4, pp. 7–14. (In Russ.).

14. Potak Ya.M. High-Strength Steels. Moscow: Metallurgiya, 1972, 208 p. (In Russ.).

15. Gladman T., Holmes B., Pickering F.B. Work hardening of lowcarbon steels. The Journal of the Iron and Steel Institute. 1970, vol. 208, no. pt 2, pp. 172–183.

16. Padilha A.F., Rios P.R. Decomposition of austenite in stainless steel. ISIJ International. 2002, vol. 42, no. 4, pp. 325–337. http://doi. org/10.2355/isijinternational.42.325

17. Pickering F.B. Physical Metallurgy and the Design of Steels. London, Applied Science Publisher Ltd., 1978, 104 p.

18. Angel T. Formation of martensite in austenitic stainless steels: effects of deformation, temperature and composition. The Journal of the Iron and Steel Institute.1954, pp. 165–174.

19. Schram R.E., Reed R.P. Stacking fault energies of seven commercial austenitic stainless steels. Metallurgical Transactions A. 1975, vol. 6, no. 7, pp. 1345–1351. http://doi.org/10.1007/BF02641927

20. De Abreu H.F.G., de Carvalho S.S., de Lima Neto P., dos Santos R.P., Freire V.N., Silva P.M. de O., Tavares S.S.M. Deformation induced martensite in an AISI 301LN stainless steel: Characterization and influence on pitting corrosion. Materials Research. 2007, vol. 10, no. 4, pp. 359–366. https://doi.org/10.1590/S151614392007000400007

21. Pushin V.G., Muryshev E.Yu., Belosludtseva E.S., Kuranova N.N., Pushin A.V., Svirid A.E., Uksusnikov A.N., Anan’ev A.I., Shevchenko V.G. Electron-microscopic study of structural-phase transformations in stainless steel 12Kh18N10T subjected to high-frequency hydrodynamic action under high pressure. Fundamental’nye issledovaniya. Seriya: Tekhnicheskie nauki. 2017, no. 10, pp. 255–260. (In Russ.).

22. Barbucci A., Dellucchi M., Panizza M., Sacco M., Cerisola G. Electrochemical and corrosion behaviour of cold rolled AISI 301 in 1M H2SO4. Journal of Alloys and Compounds. 2001, vol. 317, pp. 607–611. http://doi.org/10.1016/S0925-8388(00)01396-7

23. Ozgowicz W., Kurc A., Kciuk M. Effect of deformation-induced martensite on the microstructure, mechanical properties and corrosion resistance of X5CrNi18-8 stainless steel. Archives of Materials Science and Engineering. 2010, vol. 43, no. 1, pp. 42–53.

24. He S., Jiang D., Sun Z. Effect of deformation-induced martensite on protective performance of passive film on 304 stainless steel. International Journal of Electrochemical Science. 2018, vol. 13, no. 5, pp. 4700–4719. https://doi.org/10.20964/2018.05.11

25. Monrrabal G., Bautista A., Guzman S., Gutierrez Cr., Velasco Fr. Influence of the cold working induced martensite on the electrochemical behavior of AISI 304 stainless steel surfaces. Journal of Materials Research and Technology. 2019, vol. 8, no. 1, pp. 1335–1346. https://doi.org/10.1016/j.jmrt.2018.10.004

26. Barbucci A., Cerisola G., Cabot P.L. Effect of cold-working in the passive behavior of 304 stainless steel in sulfate media. Journal of the Electrochemical Society. 2002, vol. 149, no. 12, pp. B534–B542. https://doi.org/10.1149/1.1516774