The effect of hydrogen charging on the mechanical properties and fracture mechanisms of high-nitrogen chromium-manganese steels after age-hardening

Keywords: high nitrogen steel, hydrogen embrittlement, austenite, age-hardening, fracture, discontinuous decomposition

Abstract

Currently, many technical problems require a comprehensive study of the properties of materials operating in hydrogen-containing environments. The authors investigated the effect of age-hardening on the hydrogen embrittlement and fracture micromechanisms of high-nitrogen austenitic Fe-23Cr-17Mn-0.1C-0.6N (wt. %) steel. For this purpose, using heat treatments, the authors formed in specimens of Fe-23Cr-17Mn-0.1C-0.6N steel the structural phase states characterized by different distribution and content of dispersed phases. The experiment determined that the accumulation of hydrogen atoms occurs predominantly in the grains in solution-treated specimens without dispersed phases. This causes the effects of solid solution hardening and leads to a change in the micromechanism of steel fracture from a ductile dimple fracture in the absence of hydrogen to a transgranular fracture by the quasi-cleavage mechanism in hydrogen-charged specimens. It was established that the discontinuous decomposition of austenite with the formation of Cr2N cells and austenite depleted in nitrogen, predominantly along the grain boundaries causes the formation of a large fraction of interphase (austenite/Cr2N particles) boundaries. Cells of discontinuous decomposition promote hydrogen accumulation along the grain boundaries and cause brittle intergranular fracture of hydrogen-charged specimens during plastic deformation. The study showed that in specimens with the discontinuous decomposition of austenite both along the grain boundaries and spreading into the grain body, plenty of intragranular interphase boundaries (Cr2N plates in austenite) are formed, which causes the formation of a transgranular brittle fracture in the hydrogen-charged specimens.

Author Biographies

Marina Yu. Panchenko, Institute of Strength Physics and Materials Science of Siberian Branch of Russian Academy of Sciences, Tomsk (Russia)

postgraduate student, junior researcher of the Laboratory of local metallurgy in additive technologies

Anastasiya S. Mikhno, National Research Tomsk Polytechnic University, Tomsk (Russia)

student

Irina A. Tumbusova, National Research Tomsk Polytechnic University, Tomsk (Russia)

student

Galina G. Maier, Institute of Strength Physics and Materials Science of Siberian Branch of Russian Academy of Sciences, Tomsk (Russia)

PhD (Physics and Mathematics), researcher of the Laboratory of physics of structural transformations

Valentina A. Moskvina, Institute of Strength Physics and Materials Science of Siberian Branch of Russian Academy of Sciences, Tomsk (Russia)

postgraduate student, junior researcher of the Laboratory of local metallurgy in additive technologies

Evgeny V. Melnikov, Institute of Strength Physics and Materials Science of Siberian Branch of Russian Academy of Sciences, Tomsk (Russia)

junior researcher of the Laboratory of local metallurgy in additive technologies

Sergey V. Astafurov, Institute of Strength Physics and Materials Science of Siberian Branch of Russian Academy of Sciences, Tomsk (Russia)

PhD (Physics and Mathematics), senior researcher of the Laboratory of physics of structural transformations

Elena G. Astafurova, Institute of Strength Physics and Materials Science of Siberian Branch of Russian Academy of Sciences, Tomsk (Russia)

Doctor of Sciences (Physics and Mathematics), leading researcher of the Laboratory of physics of structural transformations

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Published
2020-03-28
Section
Technical Sciences