Hydrogen embrittlement and micro-damage in notched specimens of progressively cold-drawn pearlitic steel wires

Cold-drawn pearlitic steel wires are highly susceptible to hydrogen assisted fracture (HAF) related phenomena in the presence of hydrogenating environments. A widely spread test method for estimating such a phenomenon is the constant extension rate tensile (CERT) test using notched samples under cathodic electrochemical conditions. In this paper, a global study of the fracture process of progressively cold-drawn pearlitic steel wires subjected to CERT testing is carried out by analysing diverse parameters: (i) triaxiality in terms of the samples notch geometry, varying the parameters that define a circumferentially round notched wire (notch radius and notch depth); (ii) the CERT test loading rate; (iii) the level of microstructural damage and anisotropy caused during a commercial cold drawing. The obtained results allow determining the influence of each factor on the HAF of cold-drawn pearlitic steel wires and, in addition, defining four micromechanical models in terms of diverse micro fracture maps representing the fracture events.