Hydrogen-related fracture behaviors in low carbon (Fe-0.1 wt% C) and medium carbon (Fe-0.4 wt% C) martensitic steels were investigated through crystallographic orientation analysis using electron backscattering diffraction (EBSD). The specimens with lower strength exhibited transgranular fracture of which fractured surface consisted of facets parallel to {011} planes of martensite. On the other hand, the macroscopic shape of the fracture surfaces of the specimens with higher strength was intergranular-like. However, the EBSD orientation analysis revealed that many parts of the intergranular-like fracture surface were composed of the facets parallel to {011} planes of martensite. This suggested that the hydrogen-related fracture of the specimens with higher strength was not an exact intergranular fracture, but the fracture propagating along {011} planes of martensite within the prior austenite grains. The characteristics of the fracture surfaces implied that plastic deformation enhanced by hydrogen played an important role in hydrogen-related fracture in martensitic steels.
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