Factors affecting Type IV creep damage in Grade 91 steel welds

Differences in parent material heat treatment and composition apparently have remarkably little influence on the creep life of the heat affected zone (HAZ). Thus, tendency for Type IV cracking in the fine grained or intercritically heat treated regions of the HAZ does not appear to directly depend on the strength of the base steel. However, the current work indicates that the angle of the weld preparation changes the measured cross weld creep life. The results presented suggest that both development of residual stresses and the local properties of the constituent zones in the HAZ influence the tendency for Type IV damage in martensitic steels.