Hydrogen Embrittlement of Low Carbon Structural Steel

Hydrogen damage of steels: A case study and hydrogen embrittlement model

“…6. This indicates the material brittleness and change in the dominant hydrogen embrittlement mechanism, which was confirmed by impact toughness testing and fractographic studies of the fractured surface in the Charpy specimens [6]. The abrupt change in mechanical properties is a function of the hydrogen content in the metal, whereby it appears in exceeding the "critical hydrogen concentration" [6,12,21,27].…”

“…When reaching a critical hydrogen concentration, different authors suggest that different phenomena occur in steel: changes in the damage mechanism from decohesion to the formation of micro crevices at the grain boundaries [29]; local cracking initiation -establishment of the local fracture criteria [30] and critical loss of the material local strength at the notch in the presence of hydrogen [27]. In this study, the term ''critical hydrogen concentration'' defines the concentration level which causes critical drop in the impact strength of the material and sharp ductile-brittle fracture transition [6,12,21] in the presence of hydrogen. Also, such an interpretation allows the establishment of the hydrogen embrittlement model based on simultaneous action of both HELP and HEDE mechanisms in the investigated St.20 steel.…”

“…A critical experiment that would allow realistic simulation of the kinetics of the development of a certain type of hydrogen damage, which is in full compliance with the actual kinetics in the components of industrial plants exposed to hydrogen during service, is very difficult to conduct [6].…”

“…Recently, simultaneous action of the HEDE and HELP mechanisms were detected, depending on the local concentration of hydrogen in investigated low carbon steel [6]. However, the overview of the hydrogen embrittlement phenomena in steels under various conditions is still unclear.…”

“…The experimental research was conducted in two phases: a case study and failure analysis of the boiler evaporator tube sample and a subsequent -postmortem analysis of the viable hydrogen embrittlement mechanisms in the investigated steel, which are unevenly enriched with hydrogen as a result of the development of intensive and uneven local hydrogenation of the tube metal during boiler exploitation. A comprehensive case study and failure analysis of the boiler evaporator tube damaged during service due to the development of the hydrogen-induced corrosion process [2,6] and the high temperature hydrogen attack (HTHA) damage mechanism were carried out. A special experimental concept was applied during subsequent postmortem analysis of the viable hydrogen embrittlement mechanisms in investigated St.20 steel, unevenly saturated with hydrogen due to the effect of HTHA, as a main mechanism responsible for the destruction of evaporator tubes during boiler exploitation.…”