Influence of bulk and grain boundary phosphorus content on hydrogen induced cracking in low strength steels

The influence of bulk and grain boundary phosphorus content in carbon-manganese-steels was studied by constant extension rate test method in 1 m H₂SO₄ solution under cathodic polarisation. The hydrogen activity and uptake in the samples was measured using the electrochemical permeation technique. The susceptibility towards hydrogen induced cracking (HIC) increased with phosphorus content, the steel containing lower manganese was found to be more susceptible to HIC. The mode of cracking was mostly transgranular. The effect of phosphorus is related to the bulk content and not to the grain boundary concentration. The susceptibility towards HIC is directly related to the hydrogen uptake which increases with the phosphorus content and decreases with the manganese content of the steels.