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

Simple Pt-enriched gamma + gamma' coatings (16-19 at.% Al) were fabricated on Rene 142 and single-crystal N5 Ni-based superalloys by electroplating a thin layer of Pt followed by a difftision treatment in vacuum at 1175 degrees C. By introducing a secondary short-term aluminizing step via pack cementation with NaCl activator, enriched gamma + gamma' coatings were achieved with an increased Al content (similar to 22 at.% Al). The changes in composition profiles between the simple and enriched gamma + gamma' coatings were discussed. Incorporation of reactive elements, such as Hf, into the gamma + gamma' coating during the aluminizing process also was explored. The cyclic oxidation performance of the enriched gamma + gamma' coatings was evaluated at 1100 degrees C. (c) 2007 Elsevier B.V. All rights reserved.