Hydrogen Diffusion Analysis of Crack Tip of Titanium Oxide Alloy

Models that describing hydrogen permeation through a thin TiO₂ film covering on crack tip were developed based on a mass-balance equation consisting of diffusion and the stress state. The models were numerically simulated with a blunting crack tip on plate by finite element method in COMSOL. The effects of oxide film thickness and stress on the diffusion of hydrogen were discussed. The results show that the hydrogen penetrates into the crack tip and diffuses in it are suppressed dramatically by the introduction of film and the increases in thickness. The hydrogen penetration decreases with the increasing applied stress, which relieves the enrichment of hydrogen converged to crack tip. Moreover, the hydrogen diffusion caused by stress gradient is more significant at lower concentration.