Low-temperature carburizing improves hydrogen embrittlement resistance of cold worked 304 austenitic stainless steel

Journal article, 2025

Cold deformation-induced martensitic transformation in 304 austenitic stainless steel (ASS) increases its susceptibility to hydrogen embrittlement (HE). In this study, low-temperature carburizing (LTC) was performed on cold worked 304 ASS. Its effect on the mechanical properties and HE was investigated by electrochemical cathodic hydrogen charging and slow strain rate tensile test. Microstructure, fractography, and hydrogen uptake were analyzed to examine the hydrogen-induced failure. It has been found that LTC introduced the expanded austenite on the steel surface, which increased strength and surface hardness but reduced the elongation. LTC increased the initial strain hardening rate and suppressed strain-induced martensitic transformation, showing higher strain rate sensitivity. Hydrogen uptake caused loss of ductility and formation of a quasi-cleavage layer with some cracks on the surface of the steel. The HE resistance was significantly improved by LTC treatment. Cold-worked 304 showed a higher HE index due to the martensitic transformation and a higher hydrogen concentration. The remarkably reduced susceptibility to HE by LTC treatment was attributed to the carbon stabilized austenite and consequently inhibited martensite transformation, as well as compressive stress in the expanded austenite. These factors reduce hydrogen diffusion and hydrogen uptake.