An investigation into Hydrogen-Induced Cracking and Delamination

Abstract

In this work, we investigate the growth rate of cracks caused by the diffusion and accumulation of Hydrogen within metals. Hydrogen-induced cracking (HIC) begins when hydrogen is absorbed through the lattice structure of a metal in the form of singular protons. Once incorporated into the lattice, these protons may reach any cracks, voids or imperfections within the metal. At this point, the protons combine with electrons from the surroundings as well as with other recombined hydrogen ions to form molecular Hydrogen. This leads to an accumulation of molecular hydrogen within the void as the molecular hydrogen is both too large to diffuse back through the metal and more stable than the protons that could diffuse out. As a result, this accumulation causes a buildup of pressure within the void and causes further fractures. The scope of this paper includes an investigation into this phenomenon both under ideal and real gaseous conditions as well as into two mechanisms by which this can occur. The first is internal cracking inside the material and the second is delamination, where the cracking occurs near the surface of the metal or at the threshold between a metal and its coating.