Hydrogen-Related Fracture Behavior under Constant Loading Tensile Test in As-Quenched Low-Carbon Martensitic Steel

This study investigated the hydrogen-related fracture behavior in as-quenched low-carbon martensitic steel under a constant loading tensile test with various applied stresses. We found that the fracture time in the constant loading tensile test decreased as the applied stress and hydrogen content increased. The fracture surface topography analysis revealed that when the applied stress was low, the intergranular fracture was initiated around the side surface of the specimen and gradually propagated into the inner part of the specimen. In contrast, several intergranular fractures were separately initiated inside the specimen when the applied stress was high. The mode of hydrogen-related fracture was controlled by the fracture stress and not by the global hydrogen content inside the specimen. Increasing the global hydrogen content caused a decrease in the duration required for the accumulation of critical local hydrogen concentration at the fracture initiation site (prior austenite grain boundary). Accordingly, we propose that the local state at the crack initiation site is constant under a given applied stress, even when the global hydrogen content is different.

Automated summary

This study investigates the hydrogen-related fracture behavior of as-quenched low-carbon martensitic steel under constant loading tensile tests. The findings suggest that the fracture time decreases with increasing applied stress and hydrogen content. The analysis of fracture surface topography reveals that intergranular fractures initiate from the side surface and propagate into the inner part of the specimen at low stress, while several intergranular fractures are separately initiated inside the specimen at high stress levels. The mode of hydrogen-related fracture is influenced by fracture stress rather than the global hydrogen content.