Fracture of steel at different stages of hydrogen embrittlement

Abstract

1. In places of segregation in a polycrystalline body hydrogen facilitates microplastic deformation under the influence of torsional stresses in the first stage and the formation of microcracks under the influence of normal stresses, which reduces the capacity of steel for even deformation and strengthening. 2. The susceptibility of steels to hydrogen embrittlement varies with the distribution of hydrogen, since local hydrogen weakening increases the sensitivity of steel to overloading and premature brittle failure. 3. In the second stage of reversible embrittlement the capacity of the steel for even strengthening is reestablished, although hydrogen bubbles begin to form, reducing the ductility, and the characteristic signs of the stage of irreversible embrittlement appear. 4. In conformity with the rate at which brittleness develops, the morphology of the fracture also changes. The original ductile fracture changes to typical brittle fracture during reversible embrittlement. With the development of irreversible embrittlement the fracture becomes mixed—brittle sections along with ductile sections. 5. The most even structure, chemical composition, fields of internal stress, distribution of structural components, and dispersity of structural components increase the resistance of steel to hydrogen embrittlement.