Cathodic Hydrogen Charging of High-Strength, Low-Alloyed AISI 4140 Steel

The effect of atmospheric corrosion on the hydrogen degradation of chromium-molybdenum high-strength 4140 studs was simulated by cathodic charging of standard tensile specimens in acidic 5% sodium chloride (NaCl) electrolyte. Heat-treated steel at 750°C, with ferrite and coarse pearlite microstructure, exhibited the most damage to strength and percent elongation properties. All specimens showed ductile cup and cone fracture mode with no cracking. Some microvoids were observed at the specimens' subsurface ring that were caused by hydrogen penetration.