EFFECT OF MATERIAL MICROSTRUCTURE ON CREEP DAMAGE FORMATION BEHAVIOR FOR NI-BASE DIRECTIONALLY SOLIDIFIED SUPERALLOY

摘要

Ni-base directionally solidified superalloy strengthened by γ' precipitates have been developed as a gas turbine blade. However, it is difficult to detect creep damage such as creep voids by conventional observation techniques. It is important to clarify the creep damage behavior for Ni-base superalloy. In this study, creep crack growth tests for Ni-base directionally solidified superalloy CM247LC were conducted using the in-situ observational system. Additionally, the metallographical investigation was conducted on crept specimen using EBSD analysis and relationship between creep crack growth path and material microstructure were clarified. And, in order to clarify the difference of creep crack growth behavior, the designed two-dimensional elastic-plastic creep finite element analyses were conducted for the model with grain distribution obtained by EBSD analysis.