The influence of the tempering temperature on hydrogen embrittlement in carbonitrided modified SAE 10B22 steel

The modified SAE 10B22 steel has high hardenability, which provides its use in special engineering applications, such as in self-drilling screws, with carbonitrided layer, quenched and tempered. However, these components are susceptible to hydrogen embrittlement, which can cause damage to structural components. In addition, the study of the behavior regarding to hydrogen embrittlement of components with carbonitrided layer has not been done hitherto. In this work the tempering temperature influence on hydrogen embrittlement of modified SAE 10B22 steel, was evaluated after a carbonitriding process. Standard samples and M4 x 50 screws were tested. A galvanostatic circuit was used for hydrogen charging of the samples, which were characterized by low-strain tensile test and the samples fracture were analyzed by SEM. The obtained results demonstrate that by lowering tempering temperatures, the hydrogen-loaded samples presented a greater loss of mechanical properties and greater changes of the micromechanics of fracture. In addition, the geometry of the screw was more prone to the deleterious effects of the hydrogen charging than the conventional specimens.