Marked Degradation of Tensile Properties Induced by Plastic Deformation after Interactions between Strain-Induced Martensite Transformation and Hydrogen for Type 316L Stainless Steel

Keisuke Nicho,Ken’Ichi Yokoyama

doi:10.3390/met10070928

Abstract

Marked degradation of tensile properties induced by plastic deformation after dynamic interactions between strain-induced martensite transformation and hydrogen has been investigated for type 316L stainless steel by hydrogen thermal desorption analysis. Upon modified hydrogen charging reported previously, the amount of hydrogen desorbed in the low temperature range increases; the degradation of tensile properties induced by interactions between plastic deformation and hydrogen at 25 °C or induced by interactions between martensite transformation and hydrogen at −196 °C occurs even for the stainless steel with high resistance to hydrogen embrittlement. The hydrogen thermal desorption behavior is changed by each interaction, suggesting changes in hydrogen states. For specimen fractured at 25 °C, the facet-like morphology and transgranular fracture are observed on the outer part of the fracture surface. At −196 °C, a quasi-cleave fracture is observed at the initiation area. Modified hydrogen charging significantly interacts both plastic deformation and martensite transformation, eventually enhancing the degradation of tensile properties. Upon plastic deformation at 25° C after the interactions between martensite transformation and hydrogen by straining to 0.2 at −196 °C, cracks nucleate in association with martensite formed by the interactions at −196 °C and marked degradation of tensile properties occurs. It is likely that the interactions between martensite transformation and hydrogen induce damage directly related to the degradation, thereby affecting subsequent deformation. Upon dehydrogenation after the interactions between the martensite transformation and hydrogen, no degradation of tensile properties is observed. The damage induced by the interactions between martensite transformation and hydrogen probably changes to harmless defects during dehydrogenation.

Highlights

Austenitic stainless steels are expected to be used as structural materials for hydrogen energy systems, including storage tanks, containers, and line pipes exposed to gaseous and liquid hydrogen for hydrogen service at low temperature, because of their high resistance to hydrogen embrittlement [1,2].The resistance to hydrogen embrittlement for austenitic stainless steels depends on Ni equivalent orMd30 [3,4,5,6,7,8]
Using modified hydrogen charging [24], we have demonstrated that the amount of hydrogen thermally desorbed in the low temperature range increases, eventually considerably enhancing the hydrogen embrittlement for type 304 stainless steel
A commercially available type 316L stable austenitic stainless steel sheet subjected to solution heat treatment at 1120 ◦ C after cold working with a thickness of 0.50 mm was used

Summary

Introduction

Austenitic stainless steels are expected to be used as structural materials for hydrogen energy systems, including storage tanks, containers, and line pipes exposed to gaseous and liquid hydrogen for hydrogen service at low temperature, because of their high resistance to hydrogen embrittlement [1,2].The resistance to hydrogen embrittlement for austenitic stainless steels depends on Ni equivalent orMd30 [3,4,5,6,7,8]. Austenitic stainless steels are expected to be used as structural materials for hydrogen energy systems, including storage tanks, containers, and line pipes exposed to gaseous and liquid hydrogen for hydrogen service at low temperature, because of their high resistance to hydrogen embrittlement [1,2]. The resistance to hydrogen embrittlement for austenitic stainless steels depends on Ni equivalent or. For type 316L stainless steel containing more than 12 mass% Ni, the resistance to hydrogen embrittlement is considered to be superior from the results obtained by conventional cathodic hydrogen charging or gas charging [4,5,6,7,8,9]. No significant hydrogen embrittlement occurs except at around −70 ◦ C [4,13,14,15,16].

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