Microstructural and crystallographic study of hydrogen-assisted cracking in high strength PSB1080 steel

The microstructural and crystallographic study of hydrogen-assisted cracking in high strength PSB1080 steel was conducted. The results indicate that the mechanical properties of PSB1080 steel are seriously deteriorated in the presence of hydrogen, which is ascribed to the coupling effect of hydrogen-assisted cracking from the O-Al-Si-Ca inclusion and accelerated phase transformation from the austenite to the martensite due to hydrogen. The hydrogen uncharged sample exhibits dimple fracture pattern, whereas the fracture surface of hydrogen charged sample consists of three zones, i.e., quasi-cleavage zone, a mixed zone of quasi-cleavage and dimple as well as dimple zone. Crystallographic orientation analysis beneath the three zones demonstrates that the proportion of low angle grain boundary is the highest, followed by high angle grain boundary and then medium angle grain boundary, and the high Kernel Average Misorientation region facilitates hydrogen-assisted crack propagation. Additionally, the grains oriented with {001}//ND, {110}//ND, {123}//ND exhibit the high possibility of hydrogen-assisted cracking. This suggests that these oriented grain textures should be reduced to design the resistance-hydrogen embrittlement alloys.