Synthesis and oxidation performance of Al-enriched γ + γ′ coatings on Ni-based superalloys via secondary aluminizing

“Simple” Pt-enriched γ + γ′ coatings (16–19 at.% Al) were fabricated on René 142 and single-crystal N5 Ni-based superalloys by electroplating a thin layer of Pt followed by a diffusion treatment in vacuum at 1175 °C. By introducing a secondary short-term aluminizing step via pack cementation with NaCl activator, “enriched” γ + γ′ coatings were achieved with an increased Al content (∼ 22 at.% Al). The changes in composition profiles between the simple and “enriched” γ + γ′ coatings were discussed. Incorporation of reactive elements, such as Hf, into the γ + γ′ coating during the aluminizing process also was explored. The cyclic oxidation performance of the “enriched” γ + γ′ coatings was evaluated at 1100°C.