Time-dependent triaxiality effects on hydrogen-assisted micro-damage evolution in pearlitic steel

Abstract

This paper offers a detailed analysis of the hydrogen-assisted micro-damage (HAMD) region in axisymmetric round-notched samples of high-strength eutectoid steel under hydrogen embrittlement environmental conditions. Emphasis is placed on the microscopic appearance and the evolution of such a microscopic topography from the initiation (sub-critical) to the fracture (critical) point. The use of very different notched geometries -with the subsequent various triaxial stress distributions in the vicinity of the notch tip- allows an analysis of the influence of stress state on hydrogen diffusion and micro-cracking. In all cases, the microscopic appearance of the hydrogen-affected zone resembles micro-damage, microcracking or micro-tearing due to hydrogen degradation. © 2012 ISIJ.