EFFECT OF CoCrAlY COATING ON THERMO-MECHANICAL FATIGUE OF INCONEL 738LC

摘要

The purpose of this study is to clarify the effect of CoCrAlY coating on thermo-mechanical fatigue (IMF) life of IN738LC. Biaxial in-phase and out-of-phase TMF tests at temperature between 450C and 850C were carried out in addition to a blade waveform tests in which temperature and strain histories of an actual gas turbine blade are simulated. Failure life of coated specimens under the in-phase condition is longer than that of without coated specimens. On the other hand, failure lives of the coated specimens under the out-of-phase and blade waveform tests are approximately 1/2 of without coated specimens. It was suggested from failure surface observation that crack initiation period in the coating is shorten by the difference of deformation behavior between the substrate and the coating, and that crack propagation rate in the substrate of the coated specimen is accelerated by the cracking of the coating compared with the crack propagation rate of the without coated specimen.