Abstract
An iridium-tantalum modified aluminized (Ir-Ta-Al) coating obtained by a two-step process is investigated. Ir-71 at.% Ta alloy was first coated on a nickel-base single-crystal superalloy TMS-75 by an electron beam physical vapor deposition (EB-PVD), and the resultant Ir-Ta alloy coating on the TMS-75 was treated by a conventional low-activity pack-cementation aluminizing process. It is found that a triplex layer structure, Ir-Ta alloy layer/β-NiAl/Al-diffusion zone, is formed in the order from the surface. In order to assess the oxidation resistance of the coated material, cyclic oxidation tests were carried out at 1373 K in air. It is found that Ir-Ta-Al coated TMS-75 had better thermal cyclic oxidation resistance than simply aluminized TMS-75. The microstructural evolution caused by the interdiffusion of solute elements shows remarkable difference on the precipitation of detrimental phases such as topologically close-packed (TCP) phase. The precipitation of TCP phase in the Ir-Ta-Al-coated TMS-75 was limited only within 180 μm in depth from the surface, whereas in the simply aluminized TMS-75, such detrimental phases were precipitated to the depth of more than 300 μm from the surface, indicating that the Ir-Ta-Al coating functions as an effective diffusion barrier for the alloying elements.
Original language | English |
---|---|
Pages (from-to) | 62-69 |
Number of pages | 8 |
Journal | Surface and Coatings Technology |
Volume | 168 |
Issue number | 1 |
DOIs | |
Publication status | Published - 2003 May 1 |
Externally published | Yes |
Keywords
- Aluminized coating
- Diffusion barrier
- EB-PVD
- Ir-Ta alloy
- Ni-base superalloy
ASJC Scopus subject areas
- Chemistry(all)
- Condensed Matter Physics
- Surfaces and Interfaces
- Surfaces, Coatings and Films
- Materials Chemistry