Effect of hydrogen on the kinetics and mechanism of fatigue crack growth in structural steels

We analyze the effect of hydrogen on the growth of fatigue cracks in structural steels depending on their strength and testing temperature. For low temperatures (T≤200°C), the effect of hydrogen is ambiguous and depends both on mechanical strength and the level of loading. Under high loads, the effect of hydrogen is similar to that of corrosive environments and is often called hydrogen embrittlement. Under low loads (near the fatigue threshold), the effect of hydrogen depends on the strength of steel and results in smaller crack closures and decreased resistance to normal cleavage fracture or increased resistance to shear for high-strength and low-strength steels, respectively. The effect of hydrogen is unambigous at high temperatures (T≥400°C) and can be described as a decrease in shear resistance and an increase in the fatigue crack-growth rates.