A novel approach to assess hydrogen embrittlement (HE) susceptibility and mechanisms in high strength martensitic steels

TL;DR

This paper introduces a rapid four-point bending test to evaluate hydrogen embrittlement susceptibility in high strength martensitic steels, providing quick, reliable insights into HE mechanisms and effects.

Contribution

The study presents a novel rapid testing method combined with fractographic and mechanistic analysis to assess HE susceptibility in martensitic steels.

Findings

The rapid test effectively identifies HE susceptibility.

Hydrogen pre-charging influences fracture behavior.

Finite element analysis elucidates stress and hydrogen distribution.

Abstract

A rapid fracture test in four-point bending is proposed to assess hydrogen embrittlement (HE) susceptibility of high strength martensitic steels. The novelty of this technique is the rapid rate of loading, whereas conventional approaches require prolonged slow strain rate testing. The essential fractographic features required to identify the mechanisms of HE failure remain evident, despite the fast loading conditions. To demonstrate these attributes, two quenched and tempered steels at two different strength levels were tested, with and without pre-charging of hydrogen. Stress coupled hydrogen diffusion finite element analysis (FEA) was performed to calculate both stress and hydrogen concentration distributions. In addition to fractographic analysis, a mechanistic description rooted in hydrogen enhanced decohesion (HEDE) mechanism was used to corroborate the mechanical test data. The study shows that the approach is capable of quantifying HE susceptibility by being responsive to key factors affecting hydrogen induced fracture, thus developing further understanding on the HE of martensitic steels.