It is well-known that boron increases the hardenability in steels. More recently, it has also been highlighted that B improves the resistance to hydrogen embrittlment in steels, which is the topic of this study. Mechanical tests with digital image correlation show an improvement of the boron-doped steel when it is pre-charged with hydrogen. Additional analysis has been made through and scanning electron microscope (SEM), showing that boron in prior austenite grain boundaries avoids the intergranular fracture of steel induced by hydrogen incorporation.

Further experiments are conducted at low tempering temperature to allow the remaining B in solid solution to segregate in other martensitic interfaces. This boron segregation aims to improve even more the resistance of boron-doped steels to hydrogen embrittlement. The microstructure is analysed through atom probe tomography, SEM and thermo-desorption spectroscopy to understand the mobility of boron in steel and avoid any formation of boride precipitates particularly detrimental for the materials. The discussion focusses also on how B can modify the trapping of H in grain boundaries with ab initio calculations determining the interaction energy between hydrogen and grain boundary in boron-doped and boron-free grain boundaries.