Influence of the Coating Brittleness on the Thermomechanical Fatigue Behavior of a \(\upbeta \) -NiAl Coated R125 Ni-Based Superalloy

The brittleness of an aluminide diffusionDiffusion coating protecting a René 125 Ni-based polycrystalline superalloyPolycrystalline superalloy was investigated over a wide range of temperatures in its as-received and thermally aged form. Isothermal and thermal cycled aging were performed on the coated system at a maximum temperature of 1100  \( ^{\circ }\text {C}\) . MicrostructureMicrostructure evolutions and damage initiation within the coatingCoating were characterized. Interrupted tensile tests and thermomechanical fatigueFatigue tests were conducted to document critical stress-strain conditions leading to the coatingCoating crackingCoating cracking and lifetime for the case of thermomechanical fatigue loading. Advanced digital image correlationDigital image correlations and acoustic emission techniques were used to detect coating crackingCoating cracking. Isothermal oxidationOxidation orCyclic oxidation cyclic oxidation led to improved strain-to-failure due to metallurgical evolutions and also longer fatigue life under thermomechanical fatigueFatigue conditions.