Intra-granular Distortion of 2.25Cr-1Mo Steel Crept at Various Test Conditions

For evaluating the creep damage of 2.25Cr-1Mo steel, intra-granular distortion (IGD) analysis, a method of average plastic distortion calculation in transmission electron microscope (TEM) was applied. Linear relation between creep strain and average intra-granular distortion at 843K and 108MPa reported in previous report was examined with two 2.25Cr-1Mo steels and at various creep conditions. Relations between creep strain and intra-granular distortion of tensile and stress accelerated creep test specimens were explained by single line, though temperature accelerator creep test conditions such as at 943K reduced the distortion in grains with microstructural coarsening. Two steels showed almost same distortion at stress accelerated conditions. Fine Mo2C precipitation with high dislocation density on the middle portion of 2.25Cr-1Mo steel tube used for 220, 000 hours in fossil power plant indicated the applicability of this technique for long time degradation at service condition.