Axial micro-cracking paths and locally anisotropic hydrogen embrittlement behaviour in cold drawn pearlitic steel wires

Abstract

This paper analyses the anisotropic fracture behaviour exhibited by initially-smooth samples of cold drawn pearlitic steel wires (commercial prestressing steel wires) subjected to tensile tests in aggressive environment promoted by a corrosion cell. Two testing rates were used: one moderately fast (0.1 mm/min) and another moderately slow (0.01 mm/min). The electro-chemical potential ranged between –1100 mV SCE and –1400 mV SCE (cathodic conditions) to promote hydrogen embrittlement (HE). Axial micro-cracking paths (local crack path deflection) and locally anisotropic HE behaviour was exhibited by the specimens but the phenomenon is strictly local, because the triaxiality level is not high enough to produce global crack path deflection in the presence of hydrogen. The anisotropic fracture behaviour shows marked deviations of the fracture path from the initial fracture zone till the fracture end zone, such deviations being higher than those observed in the specimens failing in inert environment.