Hydrogen-induced fast fracture in notched 1500 and 1700 MPa class automotive martensitic advanced high-strength steel

Abstract Hydrogen embrittlement of notched martensitic advanced high-strength steels was studied. Notched specimens had (i) higher tensile strength and lower ductility, and (ii) increased hydrogen sensitivity, manifested by reductions in ductility and strength. Hydrogen-induced fast fractures (HIFF) initiated when the load-controlled specimen became mechanically unstable. The HIFF velocity (61−130 m/s) was greater than the velocity of ductile fracture (46 m/s). HIFF susceptibility increased with increasing steel strength, increasing hydrogen fugacity, and decreasing stress rate. HIFF exhibited brittle features (quasi-cleavage, transgranular and intergranular fracture) in the initiation zone, suggesting hydrogen-enhanced plasticity-mediated decohesion (HEPD). These features increased in area with increasing hydrogen embrittlement.