Chromium and iridium effects on the short-term interdiffusion behaviour between Pt rich γ-γ′ bond-coatings and a Ni-Al-Cr alloy

Abstract

To cite this version:Pauline Audigié, Aurélie Rouaix-Vande Put, Hideyuki Murakami, Daniel Monceau. Chromium and iridium effects on the short-term interdiffusion behaviour between Pt rich γ-γ' bond-coatings and a Ni-Al-Cr alloy. Surface and Coatings Technology, Elsevier, 2017, 309, pp.258-265. 10.1016/j.surfcoat.2016 Open Archive TOULOUSE Archive Ouverte (OATAO) OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. Al and with Cr in such a way that Pt decreased their activities. According to the diffusion coefficient values, Pt had a greater influence on the Al activity than on the Cr one. Similarly, 2 μm of Pt and 3 μm of Pt-25Ir were deposited by electroplating on the same model alloy to investigate the effect of Ir. Heat treatments were performed in the same conditions as for Cr. Iridium slowed down the interdiffusion when compared with systems with Pt only. Iridium diffused slower toward the substrate than Pt and a lower Pt + Ir flux toward the substrate was found.As voids formed at the interdiffusion zone/substrate interface due to Kirkendall effect, this lower inward Pt + Ir flux resulted in a lower outward vacancy flux and then Ir reduced Kirkendall voids formation. Moreover, Ir decreased the Pt effect on Al activity by dilution or even gave an opposite contribution to the Pt one. This reduced the uphill diffusion of Al, delaying the α-NiPtAl phase formation. Diffusion paths of each model system were also identified after 15 min at 1100°C and all highlighted the α-NiPtAl phase formation and its aptitude to be used in TBC systems.

Performance of High-temperature Coatings : Oxidation and Interdiffusion

“…outstanding oxidation property at high temperatures [19][20][21][22][23][24]. Unfortunately, the use of Pt also gives rise to a high cost, and limits the wide application of this material [3,24,25].…”

Microstructure and Oxidation Behavior of Pt and Pt–Ir Diffusion Coatings on Ni-Based Single Crystal Superalloy

“…This study also suggests that there is still an optimal Ir content for achieving the best oxidation resistance of the pasted PtIr coatings, for instance, the pasted Pt20Ir among paste coatings. However, as in the case of electroplated coatings, 21) the oxidation properties of diffusion type of coatings are also affected by many factors, such as the compositions of coating and substrate, annealing conditions, and the process parameters. Further studies on the sintering and formation kinetics of paste coatings, and the particle diameters in the case of past coatings will be conducted.…”