A surface chemistry kinetic model of gaseous hydrogen embrittlement

Recently, Pasco and Ficalora advanced a simple model relating Stage II crack growth rates to adsorption kinetics. That model is based on the fact that the kinetics of crack growth processes in Stage II are controlled by the kinetics of the adsorption process. In the model the crack growth rates are proportional to the adsorption rate at some critical coverage of atomically adsorbed H-. The application of this model to explain the temperature and pressure effects on Stage II crack growth rates for maraging steels of two different strength levels gave very good results. That model, however, did not incorporate the exact pressure dependence for the rate of formation of the embrittling species H-. When that dependence is incorporated, the model's ability to calculate experimental results becomes extraordinary