Creep life assessment of 2.25Cr-1Mo piping steel and of its simulated HAZ material

A creep life assessment method was proposed for base metal and HAZ of 2.25Cr-1Mo steel STPA24 used in high temperature steam piping of fossil power plants. Microstructural observations and hardness measurements were carried out for base metal and simulated HAZ after thermal aging and creep testing. Simulated HAZ material showed significant softening during thermal and creep exposure, but base metal showed less softening. Hardness equation was established based on the kinetics of carbide coarsening and recovery of dislocation substructure. Creep damage was evaluated by damage mechanics in combination with softening equation and creep constitutive equation. The proposed method can be applied to assess creep life of Cr-Mo steel HAZ in actual components.