Effect of Hf-Doped MCrAlY Alloy on the Structure and Properties of Thermally Grown Oxide Layer

The NiCoCrAlY and NiCoCrAlYHf bond layer alloy was prepared by vacuum melting, followed by the deposition of a ZrO 2 -7%Y 2 O 3 (7YSZ) ceramic coating on its surface using atmospheric plasma spraying. The cyclic oxidation process of the coating was systematically investigated through extensive analytical equipment and first-principles calculations and compared with conventional NiCoCrAlY coatings. It is demonstrated that NiCoCrAlYHf coatings exhibit greater resistance to oxidation and peeling than NiCoCrAlY coatings when thermally cycled at 1050 °C in air. The reason for this difference is that Hf doping can reduce the growth rate of the thermally grown oxide (TGO). In addition, the formation of HfO 2 in the TGO layer, which delays the phase transition of Al 2 O 3 , reduces the growth of internal stresses in the coating and improves the adhesion of the TGO layer and bond strength of the interface. As a result, Hf doping significantly increases the oxidation lifetime of the coating, approximately 8 times that of NiCoCrAlY.