Oxidation Behavior of Hf+Cr Co-modified (Ni, Pt) Al Coatings at 1 100 ℃

A Hf+Cr co-modified (Ni, Pt) Al coating on single crystal alloy N5 was prepared successively via composite electroplating of Ni-Cr and Pt-Hf and then aluminizing treatment. The oxidation test of the coating was carried out at 1 100 ℃ in static air for 500 h in comparison with the ordinary (Ni, Pt) Al coating and Hf modified (Ni, Pt) Al coating. The effects of Hf and Cr elements on the oxidation resistance of the (Ni, Pt) Al coatings were studied in terms of comparison of the oxidation kinetics, phase composition and morphology after oxidation of three coatings. The results show that the Hf+Cr co-modified (Ni, Pt) Al coating had the lowest oxidation rate, the strongest oxide scale adhesion and the lightest surface rumpling in three coatings. Compared with the single Hf modified coating, the addition of Cr could synergize with Hf to reduce the growth rate of Al₂O₃ and internal stress of coating. Moreover, the Ni-Cr layer acted as a buffer layer between the (Ni, Pt) Al coating and the substrate, inhibiting the inter-diffusion behavior between the (Ni, Pt) Al coating and the substrate.