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

摘要

For evaluating the creep damage of 2.25Cr-1Mo steel, intra-granular distortion (IGP) 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 843 K and 108 MPa 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 943 K reduced the distortion in grains with microstructural coarsening. Two steels showed almost same distortion at stress accelerated conditions. Fine Mo_2C 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.