Influence of Coating on the Thermal Fatigue Resistance of a Ni-based Superalloy

In this article, the influence of a M-CrAlY polycrystalline coating on the thermal fatigue behavior of a nickel-base superalloy has been investigated. A special device using a rotating bending machine and two thermal sources has been used to perform thermomechanical tests. The two thermal sources have been set to obtain temperature variations between 750 and 1120 C in the central part of the specimens, with a frequency of 0.1 Hz. The results show a deleterious effect of the coating on the fatigue resistance. Numerical simulations have been carried out on SAMCEF to determine the thermomechanical field of the so-tested specimens. Calculated thermomechanical cycles of critical sites are associated with micro-structure evolution and damage by cracking observed on the specimens. Damage mechanisms related to the presence of the coating are discussed.