REJUVENATION PROCEDURES TO RECOVER CREEP-PROPERTIES OF NICKEL-BASE SUPERALLOYS BY HEAT-TREATMENT AND HOT ISOSTATIC PRESSING TECHNIQUES - A REVIEW

The rejuvenation procedures to recover the creep properties of nickel-base superalloys by atmospheric pressure heat treatment and hot isostatic pressing techniques have been reviewed in detail. It is very important that such treatments be applied at an optimum stage in the service life of a turbine blade. In other words, the rejuvenation procedures must be applied early enough to prevent catastrophic failures or irreparable damage and late enough to give a cost-effective benefit. The optimum stage at which to undertake a rejuvenation procedure to extend the creep lives of superalloys is immediately prior to the tertiary stage. By using these techniques it is not possible to extend the creep lives of superalloys indefinitely because of the accumulation of some "permanent" damage incurred during service conditions.