Internal reversible hydrogen embrittlement leads to engineering failure of cold drawn wire

摘要

Hydrogen embrittlement is very common type of phenomenon that causes industrial failure of steel material. It has been observed that embrittlement may also take place due to interfacial segregation of hydrogen in high strength steel, which leads to delamination or decohesion. Cold drawn high carbon steel wires are amenable to being weaker along the longitudinal planes compared to the transverse planes due to fibre-like deformation of pearlitic phases in the longitudinal direction. Hydrogen embrittlement is prone to cause spontaneous splitting in cold drawn wire. Generally, atomic hydrogen is absorbed initially by the metal surface and transforms to molecular hydrogen when the concentration reaches higher value. The molecular hydrogen accumulates in voids, pores and interfaces among many other defect sites. If these defects are not present in the vicinity of the high hydrogen areas, blisters or hair line cracks are formed to release the high pressure. Experimentally it was found that the segregation of molecular hydrogen generates 105 times atmospheric pressure at the interstitial sites [4]. During electroplating or pickling, hydrogen can enter the lattice, but it is usually diffused-out by a subsequent patenting [1] operation (heat treatment).