Hydrogen-Related Fracture Behavior under Constant Loading Tensile Test in As-Quenched Low-Carbon Martensitic Steel

Akinobu Shibata,Yuuji Kimura,Nobuhiro Tsuji,Yasunari Takeda

doi:10.3390/met12030440

Akinobu Shibata, Yuuji Kimura + Show 2 more

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https://doi.org/10.3390/met12030440

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Abstract

This study investigated the hydrogen-related fracture behavior in as-quenched low-carbon martensitic steel under a constant loading tensile test with various applied stresses. We found that the fracture time in the constant loading tensile test decreased as the applied stress and hydrogen content increased. The fracture surface topography analysis revealed that when the applied stress was low, the intergranular fracture was initiated around the side surface of the specimen and gradually propagated into the inner part of the specimen. In contrast, several intergranular fractures were separately initiated inside the specimen when the applied stress was high. The mode of hydrogen-related fracture was controlled by the fracture stress and not by the global hydrogen content inside the specimen. Increasing the global hydrogen content caused a decrease in the duration required for the accumulation of critical local hydrogen concentration at the fracture initiation site (prior austenite grain boundary). Accordingly, we propose that the local state at the crack initiation site is constant under a given applied stress, even when the global hydrogen content is different.

Highlights

Hydrogen often degrades the mechanical properties of metals and alloys; this degradation is referred to in the literature as “hydrogen embrittlement”, “hydrogen-related fracture”, “delayed fracture”, and so on [1]
The uncharged specimen did not fracture until 106 s under an applied stress of 1150 MPa
We investigated hydrogen-related fracture behavior under a constant loading tensile test in as-quenched low-carbon martensitic steel

Summary

Introduction

Hydrogen often degrades the mechanical properties of metals and alloys; this degradation is referred to in the literature as “hydrogen embrittlement”, “hydrogen-related fracture”, “delayed fracture”, and so on [1]. It is well-known that the sensitivity to hydrogen embrittlement increases with increasing strength of steels. The two typical fracture modes of hydrogen embrittlement in martensitic steels are quasi-cleavage and intergranular fractures. Crystallographic orientation analysis revealed that the hydrogen-related quasi-cleavage fracture often occurred along the {011} plane, not along the typical cleavage plane in a body-centered cubic (BCC) structure (i.e., the {001} plane) [3–8]. Intergranular fractures result in more severe brittle behavior during hydrogen embrittlement

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