Effect of PWHT cycles on fatigue crack growth and toughness of quenched and tempered pressure vessel steels

This paper reports work on the resistance to fatigue crack growth, impact toughness and CTOD fracture toughness of two types of QT steels. The parent metal region was examined for both steels, and then exposed to temperatures and times in the PWHT range. Although there was a marginal decrease in the resistance to fatigue crack growth for up to four postweld heat treatment cycles, there was a significant decrease in impact toughness and CTOD fracture toughness.