Cathodic Hydrogen Absorption and Severe Embrittlement in a High Strength Steel

Hydrogen absorption and consequent embrittlement are studied in hardened low-alloy steel tensile specimens after electrolytic hydrogenation in an aqueous solution of 4% H₂SO₄ containing arsenic. A critical arsenic content greater than 0.5 mg/liter is needed to cause poisoning. Saturation with hydrogen at a level of 5 to 6 wt ppm is readily achieved but causes a reduction in true fracture stress from 385,000 psi to as low as 35,000 psi. Much of this embrittlement is recovered when the specimens are degassed, but some permanent damage remains in the form of near-surface cracks, many of which are associated with inclusions. These cracks develop during cathodic electrolysis. Hydrogen absorption is much more rapid than is degassing at room temperature. These effects are consistent with a picture of hydrogen migration and embrittlement involving entrapment of hydrogen gas at internal interfaces.