The effect of hydrogen alloying on strain hardening and fracture of a high-nitrogen austenitic steel

E. Astafurova, V. Moskvina, N. Galchenko, E. Melnikov, G. Maier, A. Burlachenko, S. Astafurov, G. Zakharov
Received: 25 August 2017; Revised: 11 October 2017; Accepted: 23 October 2017
This paper is written in Russian
Citation: E. Astafurova, V. Moskvina, N. Galchenko, E. Melnikov, G. Maier, A. Burlachenko, S. Astafurov, G. Zakharov. The effect of hydrogen alloying on strain hardening and fracture of a high-nitrogen austenitic steel. Letters on Materials, 2018, 8(1) 71-76
BibTex   DOI: 10.22226 / 2410‑3535‑2018‑1‑71-76

Abstract

Hydrogenation leads to the formation of a gradient state in the steel Fe-17Cr-10Mn-7Ni-1V-0.09С-0.65N (wt.%): thin (<15 μm) brittle surface layer is formed on the side surfaces of the samples, which cracks during plastic flow; the central parts of the samples are destroyed in transgranular viscous mode similar to the samples destroyed without hydrogen charging. The thickness of the brittle surface layer increases and the character of the destruction changes with increasing duration of saturation of the samples with hydrogen in tension: from brittle mixed (transgranular and intergranular) after saturation for 8 and 16 hours to fully intergranular for 32-50 hours of hydrogen-charging.The effect of the duration of electrolytic hydrogenation on tensile mechanical properties and fracture behavior of fine-grained high-nitrogen austenitic steel Fe-17Cr-10Mn-7Ni-1V-0.09С-0.65N (wt.%) was investigated. Hydrogenation leads to the formation of a gradient structural state in the steel. A thin (<15 μm) brittle surface layer is formed on the side surfaces of the samples, which cracks during plastic flow. The central parts of the samples are destroyed in transgranular viscous mode similar to the samples destroyed without hydrogen charging. The thickness of the brittle surface layer increases and the character of the destruction changes with increasing duration of saturation of the samples with hydrogen: from brittle mixed (transgranular and intergranular) after saturation for 8 and 16 hours to fully intergranular for 32-50 hours of hydrogen-charging. Hydrogenation has negligible effect on the stages of the plastic flow and the yield stress of the steel, but leads to a decrease in elongation and in an ultimate tensile stress. The change in the plastic properties of the steel occurs nonlinearly: the hydrogen embrittlement index, which characterizes the change in the elongation of hydrogenated samples relative to the one without hydrogen, increases up to 24% when saturated with hydrogen up to 16 hours, and, with an increase in duration of saturation up to 50 hours, on the contrary, decreases down to 17%. The change in steel plasticity after hydrogen charging correlates with decrease in the strain-hardening rate and with a change in the cracking mode of the sample surface depending on the duration of saturation.

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