Prevention of Hydrogen Embrittlement in Steels

Abstract

The essential facts about the nature of the hydrogen embrittlement of steels have now been known for 140 years. It is diffusible hydrogen that is harmful to the toughness of iron. It follows, therefore, that the harmful influence of diffusible hydrogen can be mitigated by preventing its entry into steel or by rendering it immobile once it penetrates the material. This review deals with the methods that might be implemented to design steels and components that resist hydrogen embrittlement by reducing the intake of hydrogen or rendering it innocuous when it does penetrate the steel.

Hydrogen Traps and Hydrogen Induced Cracking in 20CrMo Steel

“…12) Therefore, it is appropriate for reducing the HE susceptibility by preventing the ingress of hydrogen or immobilizing free hydrogen by trapping them in certain sites. [13][14][15] In general, trapping sites for hydrogen are separated by reversible traps or irreversible traps with a critical binding energy value, which can be acquired by thermal desorption or permeation analysis. 16) Reversible traps include dislocations, microvoids and coherent precipitates/interfaces which can immobilize and release hydrogen at low temperatures normally below 573 K. 12) In contrary, irreversible trap absorbs hydrogen and prevent it from escaping until it reaches even higher temperature.…”

The challenges of hydrogen and metals

“…They may say it's structurally safe but if someone was hit they would have died, plain and simple. ' A central issue in the prevention of HE is the notion of immobilization of hydrogen by deep traps, designed into the microstructure [6]. These are usually transition metal carbides, many of which already play a vital role in strengthening: for example, interphase precipitates in microalloy steel.…”

Decrease in Hydrogen Embrittlement Susceptibility of 10B21 Screws by Bake Aging

“…Non-diffusible hydrogen is usually located at interphase boundaries or in dislocations and is not easily removed. This type of hydrogen atom can form hydrogen traps that limit the movement of hydrogen atoms, enhancing HE resistance [7]. In contrast, diffusible hydrogen can freely move, and easily accumulates to form hydrogen molecules which damage the host material.…”