Stress-Corrosion Cracking Investigation Of Two Low Alloy, High-Strength Steels

Laboratory stress corrosion testing with an improved test specimen configuration has been conducted on 4330M and 4340 steel billet material to evaluate grain direction and surface finish effects. The transverse grain directions were found to be the most susceptible to cracking. Surface finishing by chemical milling, electropolishing and grinding increased stress corrosion susceptibility. Surface finishing by grit blasting, shot peening and face milling increased resistance to cracking. Cracking appeared to be intergranular with respect to the prior austenite grain boundaries. Fractographic studies with the electron microscope suggest that hydrogen embrittlement and stress-corrosion cracking may be fundamentally related.