Creep Residual Life Estimation Method Based on Strain Hardening Mechanism for Precipitation Strengthened Ni-Based Alloy

To establish the creep life prediction method for Ni-based alloys, the microstructure, hardness and dislocation density measurement was done for various creep damaged samples of γ’-Ni3Al precipitation strengthened alloy, TOS1X-2. The hardness and dislocation density of creep interrupted and ruptured samples at 700℃ and 750℃ increased with creep strain and creep time. TEM analysis showed that large amount of dislocations induced by creep was present in γ matrix, and γ’ precipitates were almost free from dislocation. The hardness increase at gauge portion of specimens showed linear increase with square root of dislocation density, suggesting that hardening by creep damage obeys the Bailey-Hirsch’s strain hardening relationship. Based on this strain hardening relationship and combining the creep constitutive equation, the creep residual life of interrupted specimens was estimated with high accuracy from measured hardness.