Time-dependent Triaxiality Effects on Hydrogen-assisted Micro-damage Evolution in Pearlitic Steel

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, micro-cracking or micro-tearing due to hydrogen degradation.