Fatigue behavior of a freestanding Pt-aluminide (PtAl) bond coat at ambient temperature

The intermetallic B2-NiAl based diffusion Pt-aluminide (PtAl) bond coat is applied on aem-engine components. The coating is prone to brittle fracture, which necessitates the evaluation of its fatigue behavior. In the present study, micro-fatigue testing is conducted on freestanding 70 mu m thick PtAl coating at ambient temperature. The fatigue life is as low as 30,000 cycles and exceeds 10(6) cycles above and below the endurance limit of 248 MPa. High dislocation density, dislocation cells, and dislocation-dislocation/dislocation-precipitate interactions induce strain hardening in the coating. Micro-voids initiate by de-cohesion of precipitate/B2-matrix interface in the heavily precipitated interdiffusion zone of the coating. The intergranular propagation of micro-cracks, developed by micro-void coalescence, causes failure.