Influence of Martensitic Transformation on the Durability of TBC Systems (Invited)

Abstract

Microstructural evolution of bond coat with thermal cycling was characterized with transmission electron microscopy (TEM) and high temperature X-ray diffraction (HT-XRD) analysis. Before thermal cycling, the structure of asfabricated bond coat was confirmed to be a long-range ordered B2 β-phase. After thermal cycling to ∼28% of the cyclic life, the bond coat was found to transform into a Nirich L10 martensite (M) from its original B2 structure. The transformations, M ↔ B2, were demonstrated to be reversible and to occur on heating and cooling in each cycle. Quantitative high temperature XRD measurements verified the phase transformations produce about 0.7 % transformation strain. Finite element calculations incorporating the transformation strain indicate that the mertensitic transformation significantly influences the development of stresses and strains in TBC systems.

Experimental and Modeling Studies of Thermal Barrier Coating Failure Under Isothermal Oxidation and Solid Particle Erosion

“…Phase transformation may also take place in the bond coat of TBCs. As reported [67], before thermal cycling, the structure of as-fabricated bond coat was present as a long-range ordered B2 β-phase, but after thermal cycling to ~28 % of the cyclic life, the phase of the bond coat transferred into Ni-rich L10 martensite (M) from its original B2 structure. This transformation was reversible and occurred under heating and cooling in each cycle.…”