Abstract: Type IV cracking in heat affected zone (HAZ) of weldment is a problem for advanced high Cr ferritic heat resisting steels. It is important to predict initiation and growth of creep voids and cracks in weldment. Present paper conducted the creep crack growth tests for the welded joint and base metal of tungsten strengthened 12Cr steel. The initiation and growth properties of Type IV crack in fine-grained HAZ of weldments were clarified. On the basis of experimental results, the programs that simulate Type IV fracture have been developed. The effect of multiaxial stress condition on vacancy diffusion and crack initiation for welded joints was discussed.
Keywords: P122 steel, welded joint, Type IV fracture, creep crack growth, FEM