Published online by Cambridge University Press: 21 February 2011
Hydrogen attack and creep damage may reduce the fracture toughness as well as the strength of steels. This reduction is caused partially by the presence of cavities and microcracks at the grain boundaries. A large reduction in fracture toughness can make some components unsafe for operation. Ultrasonic tests performed on damaged samples showed a decrease in wave velocity and an increase in backscatter. The longitudinal-wave velocity decreased more than shear-wave velocity. Where the fracture toughness was reduced by 43 percent, samples with hydrogen attack showed a tenfold increase in backscatter. Such results demonstrate the potential for ultrasonic nondestructive testing to quantify damage and assess the component's remaining life.