Cyclic Oxidation Behavior of Pt Modified Nicocralyhfzr + Alniy Coating on a Ni-Based Single Crystal Superalloy

In this study, the NiCoCrAlY + AlNiY, NiCoCrAlYHfZr + AlNiY and Pt modified NiCoCrAlYHfZr + AlNiY coatings are prepared by combining arc ion plating (AIP), electroplating Pt and annealing treatment. All the coatings are composed of three different zones including an outer layer and an inner layer as well as an interdiffusion zone (IDZ), therein, the outer layer consists of β-NiAl phase with dispersed α-Cr phase and the inner layer is composed of NiCoCr-rich phase with dispersed β-NiAl phase. In addition, an Y-rich belt is formed between the outer layer and the inner layer. The cyclic oxidation behaviors of the three coatings at 1100 °C are investigated. Results indicate that Pt and Y-rich belt exhibit synergistic effect on preventing the interdiffusion between coating and substrate, thus a thinner secondary reaction zone (SRZ) forms in Pt modified NiCoCrAlYHfZr + AlNiY coating. The evolution processes of Y-rich belts in the three coatings are also discussed. Besides, a lower oxidation rate and enhanced oxide scale adherence are achieved in Pt modified NiCoCrAlYHfZr + AlNiY coating, the enhanced oxidation performance is mainly attributed to the co-segregation of Pt-Hf-Zr-Y at oxide scale grain boundaries and the synergistic effect of Pt-Hf-Zr-Y on suppressing interfacial voids growth.