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

Stacy, Justin; Zhang, Ying; Pint, Bruce A.; Haynes, J. Allen; Hazel, Brian; Nagaraj, B. A.

doi:10.1016/j.surfcoat.2007.06.053

Cited by 31 publications

(14 citation statements)

References 22 publications

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“…The Pt electroplated specimen shows γ-Ni,Pt,Al and γ'-(Ni,Pt) 3 Al structure. The microstructure of Pt diffusion coating was investigated and confirmed by other studies [4,[15][16][17]. On the other hand, in the Pt20Ir electroplated coating, γ+α two phase structure was observed instead of γ+γ' two phases.…”

Section: Resultssupporting

confidence: 67%

OXIDATION RESISTANCE AND MICROSTRUCTURE OF Pt AND PtIr DIFFUSION COATINGS ON Ni BASED SINGLE CRYSTAL SUPERALLOYS BY ELECTROPLATING METHOD

Dao¹,

Murakami²,

Lien³

2019

JST

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Blades and vanes for gas turbines, usually made of Ni-based superalloys, are exposed at very high temperature in severe oxidation and corrosion environments. Nowadays, thermal barrier coating systems (TBCs) have been applied to protect them against such severe working conditions. In this study, Pt and PtIr diffusion coatings on Ni based single crystal superalloys were fabricated by an electroplating method followed by an annealing heat treatment process. The microstructure and phase constitution of the coatings were studied by SEM/EDS and XRD methods. The cyclic oxidation test at 1150 o C was conducted to investigate the oxidation resistance of the coatings. The results showed that the addition of Ir in the coating led to the formation of α(NiPt 2 Al) phase and reduced the formation of Kirkendall voids in the coating after 100 cycle oxidation test.

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Section: Resultssupporting

confidence: 67%

OXIDATION RESISTANCE AND MICROSTRUCTURE OF Pt AND PtIr DIFFUSION COATINGS ON Ni BASED SINGLE CRYSTAL SUPERALLOYS BY ELECTROPLATING METHOD

Dao¹,

Murakami²,

Lien³

2019

JST

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“…The Pt-modified c-c¢ coatings are currently being investigated for bond coat applications. [38,39] It is believed that these coatings, which contain very low amounts of Al and also have the same structure as the substrate, are chemically and mechanically more compatible with the substrate than are the b coatings. [38,40] They have also been reported to provide adequate oxidation resistance to the superalloy substrates.…”

Section: Discussionmentioning

confidence: 99%

Formation of Secondary Reaction Zones in Diffusion Aluminide-Coated Ni-Base Single-Crystal Superalloys Containing Ruthenium

Das

Murphy

et al. 2008

Metall Mater Trans A

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The formation of secondary reaction zones (SRZs) beneath aluminide coatings in several Ru-bearing single-crystal Ni-base superalloys has been investigated. The presence of significant amounts of Ru in the superalloys did not prevent the formation of the secondary reaction zone. However, the Ru content of the alloys affected the type of refractory element-rich phase formed during the transformation. As the Ru content increased, the phase involved in the transformation shifted from the orthorhombic P to the b-RuAl phase. A differential tendency to SRZ formation was observed between the dendritic and interdendritic regions of the alloys. Significant growth of the SRZ was also observed during the high-temperature oxidation exposure of the coated alloys. The effects of the alloying elements on SRZ formation are discussed.

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“…The second stage could be a pack or CVD process to increase the Al, Cr, Hf, etc. content of the coating after Pt-plating [5,7,15,16]. The first γ+γ' coatings [3,4,9,15] made at ORNL/TTUused ~7µm Pt, the same amount as in conventional low activity chemical vapor deposition aluminide coatings [17], and a 2h vacuum anneal at 1150° or 1175°C.…”

Section: Coating Fabricationmentioning

confidence: 99%

The Performance of Pt-Modified Alumina-Forming Coatings and Model Alloys

Pint¹,

Haynes²,

More³

et al. 2008

Superalloys 2008 (Eleventh International Symposium)

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The oxidation behavior of two-phase, γ+γ' Pt diffusion coatings and model alloys has been evaluated to better understand the potential of this class of coatings for power generation applications. Coatings were deposited on both directionallysolidified alloy 142 and single crystal N5 superalloys. Fabrication issues such as initial Pt thickness and annealing temperature were evaluated. Oxidation testing was performed in both dry O 2 and with the addition of H 2 O to study the performance of γ+γ' and conventional coating materials. After exposure for 1000, 1-h cycles at 1150°C in dry O 2 , a γ+γ' coating on N5 had evolved into a thicker, almost continuous γ' layer with the Pt content dropping to ~7at.% in this layer and diffusing ~250 µm into the substrate, disrupting the γ+γ' substrate microstructure. Characterization of the oxide formed on a γ+γ' composition showed that even 30 at.%Pt did not prevent the formation of a Ni-rich spinel layer at 1200°C. In order to assist the coating development process, model alloys also were evaluated. Other Pt group metals (Pd and Ir) were evaluated as well as the addition of Cr and various Hf levels. As expected, Cr and Hf were beneficial for oxidation resistance. However, Pd was not an adequate replacement for Pt because of the multi-phase microstructure that formed. A γ+γ' composition had a 1000°C yield stress in compression that was significantly higher than γ'-Ni 3 Al or β-NiAl. Also, the thermal expansion coefficient was very similar to other Ni-Al alumina-formers. The performance of γ+γ' compositions are very promising, however, sensitivity to superalloy substrate composition, Pt interdiffusion during long-term service, spinel formation and the potential need for a secondary processing step are areas of concern for this class of coatings.

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

Cited by 31 publications

References 22 publications

OXIDATION RESISTANCE AND MICROSTRUCTURE OF Pt AND PtIr DIFFUSION COATINGS ON Ni BASED SINGLE CRYSTAL SUPERALLOYS BY ELECTROPLATING METHOD

OXIDATION RESISTANCE AND MICROSTRUCTURE OF Pt AND PtIr DIFFUSION COATINGS ON Ni BASED SINGLE CRYSTAL SUPERALLOYS BY ELECTROPLATING METHOD

Formation of Secondary Reaction Zones in Diffusion Aluminide-Coated Ni-Base Single-Crystal Superalloys Containing Ruthenium

The Performance of Pt-Modified Alumina-Forming Coatings and Model Alloys

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