Abstract
Creep and crack growth properties of W strengthened high Cr steel weldment have been investigated at 923 K. Most of the joint specimens were type IV fractured in fine‐grained HAZ and showed shorter creep lives than base metals. The relations of creep properties and precipitation and dislocation microstructures of HAZ were investigated. The effect of welding procedure on creep life and fracture behavior was clarified by creep tests of three types of welded joints. In order to analyze the effect of vacancy diffusion on type IV creep fracture, the FEM code that simulates creep crack growth behavior taking the void formation into account has been developed.