Effect of Tempering Temperature on Hydrogen Embrittlement and Carbide Morphology in 42CrMoS4 Fastener Steel

This study evaluated the effect of tempering temperature on the hydrogen embrittlement behavior and microstructure of high-strength fastener steel 42CrMoS4. To investigate the influence of tempering temperature on the microstructure, tensile properties, and hydrogen embrittlement susceptibility of 42CrMoS4, four different tempering temperatures were designed. The results showed that, as the tempering temperature increased, the strength of the steel decreased as expected, while the ductility increased accordingly; on the other hand, under the same pre-hydrogen charging conditions, the hydrogen embrittlement susceptibility of the steel decreased. These property changes can be explained by the changes in carbide morphology observed by x-ray diffraction (XRD) and transmission electron microscopy (TEM).