Improvement of hydrogen embrittlement resistance by intense pulsed ion beams for a martensitic steel

Intense pulsed ion beams (IPIB) have been applied on the surface of a lath martensitic steel with aim to improve its hydrogen embrittlement resistance and reveal the key cmaterial factors leading to failure. Hydrogen charging slow strain rate tensile tests show that IPIB can increase the ultimate fracture strength. The main fracture mode changes from intergranular fracture (untreated) to quasi-cleavage fracture (treated). Atomic probe tomography reveals that C atoms segregate at prior austenite grain boundaries for the untreated steel. After IPIB treatment, the C content at the PAGBs is reduced and high-carbon martensite forms in the treated layer, which improves the HE resistance. This study suggests that C segregation at grain boundaries is one of the main factors to cause the high HE susceptibility for the investigated lath martensitic steel and C segregation should be avoided when developing high strength steels with high HE resistance.