Characterization of the high temperature oxidation of TBC-coated oxide-dispersed β-NiAl substrates

A Y₂O₃-stabilized ZrO₂ coating on three different oxide-dispersed (Y₂O₃, ZrO₂ and Al₂O₃) β-NiAl substrates was studied to evaluate the spallation behaviour of the coating and its effect on the oxidation behavior of these alloy substrates. Spallation of the coating during cyclic testing at 1200°C primarily occurred at the Al₂O₃ scale-substrate interface and was dependent on the adhesion of the scale to the substrate. Uncoated, Y₂O₃-dispersed β-NiAl had the best Al₂O₃ scale adhesion and the coated β-NiAl substrate had the longest coating lifetime. Al₂O₃-dispersed β-NiAl exhibited the poorest scale adhesion and the coating completely spalled after two 2-hour cycles. For this model-type system, the growth of voids at the metal-scale interface appears to be critical in determining scale adhesion and thus coating lifetime.