Determination of Critical Hydrogen Concentration and Its Effect on Mechanical Performance of 2200 MPa and 600 HBW Martensitic Ultra-High-Strength Steel

Eric Fangnon,Yuriy Yagodzinskyy,Esa Virolainen,Saara Mehtonen,Pedro Vilaça,Evgenii Malictki

doi:10.3390/met11060984

Eric Fangnon, Yuriy Yagodzinskyy + Show 4 more

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https://doi.org/10.3390/met11060984

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Journal: Metals	Publication Date: Jun 20, 2021
Citations: 9	License type: CC BY 4.0

Affiliation: Aalto University, Svenskt Stål (Finland)

Abstract

The influence of hydrogen on the mechanical performance of a hot-rolled martensitic steel was studied by means of constant extension rate test (CERT) and constant load test (CLT) followed with thermal desorption spectroscopy measurements. The steel shows a reduction in tensile strength up to 25% of ultimate tensile strength (UTS) at critical hydrogen concentrations determined to be about 1.1 wt.ppm and 50% of UTS at hydrogen concentrations of 2 wt.ppm. No further strength degradation was observed up to hydrogen concentrations of 4.8 wt.ppm. It was observed that the interplay between local hydrogen concentrations and local stress states, accompanied with the presence of total average hydrogen reducing the general plasticity of the specimen are responsible for the observed strength degradation of the steel at the critical concentrations of hydrogen. Under CLT, the steel does not show sensitivity to hydrogen at applied loads below 50% of UTS under continuous electrochemical hydrogen charging up to 85 h. Hydrogen enhanced creep rates during constant load increased linearly with increasing hydrogen concentration in the steel.

Highlights

The measured hydrogen concentration increased with increasing charging time
The measured hydrogen concentration increased with increasing charging time up to up to 1.45 wt.ppm at 3.5 h
The effects of hydrogen on mechanical performance of a 600 HBW m were evaluated through constant extension rate test (CERT) and constant load test (CLT) under continuous hydrogen cha

Summary

Introduction

There is an ever-increasing need for hard and tough steels for demanding wear and impact resistance industrial applications. These include mining equipment in severe corrosion environments [1], ballistic resistance in armored and patrol vehicles, and protected buildings in civil construction [2]. It has been reported that local stresses and local hydrogen concentrations are controlling factors of the loss of fracture strength in steels [6]. The primary conditions responsible for the undesired failure depend often on dislocation process, and are controlled by hydrogen diffusion and trapping, coupled with the state of stresses in the material [7,8,9]

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