Hydrogen-induced intergranular fracture of steels

Abstract

The phenomenon of hydrogen-induced intergranular brittle fracture of steels is a result of the combination of hydrogen dissolved in the crystal lattice and embrittling impurities that had previously segregated at grain boundaries. This type of brittle cracking is a stress-controlled phenomenon and can be demonstrated in steels that have been embrittled by the elements that are responsible for temper embrittlement and tempered-martensite embrittlement. The presence of mobile hydrogen essentially facilitates the formation of an intergranular microcrack that can initiate brittle fracture. In the absence of sufficient segregated impurity, hydrogen produces enhanced cracking at relatively high stresses by concentrated plastic flow, a displacement-controlled phenomenon. Thus, the two types of hydrogen-induced cracking are fundamentally different.