Indexing the Degree of Hydrogen Embrittlement of 4340 Steel Using the Barnacle Electrode.

The barnacle electrode, an electrochemical device based on the hydrogen permeation method, was used, in conjunction with sustained load tests, to index the degree of embrittlement of 4340 steel. Flat, double notched tensile specimens of 250 ksi 1725 MPa notched tensile strength and having a K sub T of 5.6 were shown to have a critical diffusible hydrogen concentration of 1.9, 1.7, 1.4, 1.2, 0.9 and 0.5 ppm for loads of 15, 20, 25, 30, 35 and 40 percent of the notched tensile strength. Author