Failure of steels caused by hydrogen induced microcracking

A model of hydrogen induced microcracking in pressure vessel steels has bee n developed. It is assumed that the initiation of microcracks is caused by a localized increase in hydrogen concentration at inclusions. The propagati on at these site initiated microcracks results in fisheye formation and is controlled by a local stress intensity factor and fracture resistance of th e matrix. Stability of the hydrogen induced brittle microcrack is dictated by the relative increase of both these quantities. This criterion has been used for the estimation of fisheye crack size at the fracture surface as a function of temperature. The introduced dimensionless coefficient of fractu re resistance increase rate grows as the temperature increases. Very good a greement of predicted fisheye crack size with experimental fractographic ob servations has been found. (C) 1998 Elsevier Science Ltd. All rights reserv ed.