Development of Re-based diffusion barrier coatings on nickel based superalloys

✍ Scribed by T. Narita; K.Z. Thosin; L. Fengqun; S. Hayashi; H. Murakami; B. Gleeson; D. Young

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: German
• Weight: 403 KB
• Volume: 56
• Category: Article
• ISSN: 0947-5117
• DOI: 10.1002/maco.200503924

✦ Synopsis

A diffusion barrier type coating with a duplex layer structure, an inner r-(Re, W, Cr, Ni) as a diffusion barrier and outer Ni-aluminide as an Al reservoir, was formed on a Nickel based, single crystal, superalloy (TMS-82 +) and on Hastelloy X. Oxidation properties of both the alloys with or without the diffusion barrier coating were investigated in air under thermal cycling between room temperature and 1423 K for up to 360 ks. The inner r layer with a composition (at%) of ( 35-40) Re, (15 -20) W, (15 -25) Cr and (15 -25) Ni was produced by electrodeposition of Ni-70Re and Ni-20W films from aqueous solutions followed by Cr-pack cementation at temperatures between 1473 and 1573 K, and the outer Ni-alumi-nides of b-(Ni,Cr)Al + c 0 -(Ni,Cr) 3 Al was formed by electrodeposition of a Ni film, followed by Al pack cementation. After the 360 ks oxidation it was found that the structure and composition of both r layer and alloy substrate were retained with little change. Furthermore, there was little Al in the r layer. It could be concluded that the Re-based alloys such as r (Re(W),Cr,Ni) are very promising candidates as a diffusion barrier between the outer Al-reservoir layer and alloy substrate at temperature of 1423 K. It was found that the Re(W)-Cr-Ni acts as a diffusion barrier for both inward diffusion of Al and outward diffusion of alloying elements in the alloy substrate.