The effect of systematic variation of Ni:Co ratio on the oxidation behaviour of γ-γ′ Ni-Co-Al-Ti-Cr alloys

Llewelyn, Sioned; Chater, Richard J.; Jones, Nicholas; Hardy, Mark; Stone, Howard J.

doi:10.1016/j.corsci.2020.109087

Cited by 7 publications

(2 citation statements)

References 50 publications

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“…This phase is seldom observed; however, it may result from a solid-state reaction between NiO and TiO 2 [ 42 ]. Combined with CoO [ 43 ], the reaction can be described as follows: where denotes a solid. The Gibbs free energy of formation for NiTiO 3 was calculated with the expression reported by Jacob et al [ 44 ].…”

Section: Discussionmentioning

confidence: 99%

The Effect of Nb, Ta, and Ti on the Oxidation of a New Polycrystalline Ni-Based Superalloy

Wo,

Hardy,

Stone

2024

High Temperature Corrosion of mater.

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The effect of variations in Nb, Ta, and Ti concentrations in exchange for Al on the oxidation resistance of a new polycrystalline Ni-based superalloy (C19) was studied in air at 800 °C for up to 1000 h. An external scale of Ti-doped Cr2O3 and a sub-scale of discontinuous Al2O3 intrusions formed on the surface of all the studied alloys. Contrary to other reports, increasing the Nb concentration improved the oxidation performance and may have promoted the formation of a CrTaO4 layer, thereby reducing oxygen ingress. The addition of Ta also significantly improved oxidation resistance and reduced the depth of the Al2O3 intrusions. Increasing the Ti concentration did not significantly affect the oxidation performance, potentially due to the relatively low Ti concentrations investigated. Several of the studied alloys with modified Ta and Ti concentrations showed regions of continuous Al2O3 scale formation, suggesting that the compositions are in a transition regime between Cr2O3-forming and Al2O3-forming behaviour. The findings suggested that part of the Ti content in C19 could potentially be replaced with Nb, Ta and/or other elements to further enhance oxidation resistance and other desirable properties. Overall, the insights gained could serve as a guide to optimise the composition of C19 and similar alloys for enhanced oxidation resistance.

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Section: Discussionmentioning

confidence: 99%

The Effect of Nb, Ta, and Ti on the Oxidation of a New Polycrystalline Ni-Based Superalloy

Wo,

Hardy,

Stone

2024

High Temperature Corrosion of mater.

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show abstract

“…[11][12][13] The reversed trend was, however, found for exposure of two-phase Co/ Ni-base model alloys at 800 °C. [11,14] Like for conventional Ni-base superalloys, the applicability of these novel Co-base alloys with considerable Ni levels relies on coatings to guarantee their durability S.P. HAGEN, B. ABU-KHOUSA, and S. VIRTANEN are with the Chair for Surface Science and Corrosion (Insitute IV), Friedrich-Alexander Universita¨t Erlangen-Nu¨rnberg, 91058 Erlangen, Germany.…”

Section: Introductionmentioning

confidence: 99%

Influence of the Co/Ni Ratio and Dendritic Segregations on the High-Temperature Oxidation Resistance of Multinary Co-Rich Superalloys at 850 °C and 1050 °C

Hagen

Weiser

Abu-Khousa

et al. 2022

Metall Mater Trans A

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Excellent inherent oxidation resistance is a prerequisite for the use of superalloys in many high-temperature applications. To achieve this goal, typically continuous alumina and chromia scale growths are assured through sufficient Cr and Al additions. Since the intended γ/γ′-microstructure of superalloys is only stable within a certain compositional window, the maximum concentrations of these protective scale forming elements are, however, dependent on the overall alloy composition. The latter is a severe drawback, especially for Co-rich superalloys, as for these the maximum content often is insufficient for reaching the desired continuous scale growth. In recent years, the addition of significant Ni levels was identified to improve the high-temperature oxidation properties in the case of simple model alloy systems. In this study, we compare the high-temperature oxidation behavior of two complex Co-rich multinary single-crystalline γ/γ′-strengthened superalloys that only differ regarding their Co/Ni ratios to the commercial Ni-base superalloy CMSX-4. Therefore, time-resolved isothermal gravimetric analysis (TGA) in synthetic air at 850 °C and 1050 °C for 100 hours, scanning electron microscopy analysis (SEM), and electron probe microanalysis (EPMA) were conducted. The results point out that a high Co-content beneficially affects the oxidation resistance at 850 °C, meaning that the Ni-base CMSX-4 is slightly outmatched by the Co-rich competitors. In contrast, at 1050 °C, the commercial (most Ni-rich) alloy performed best and, clearly, an increasing Co-content was identified to deteriorate the oxidation resistance. This temperature-dependent influence of the nominal Co/Ni ratio on oxidation resistance is shown to be especially pronounced for dendritic regions. Consequently, the latter could be identified to especially determine the overall oxidation kinetics.

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Effect of Al addition on intergranular embrittlement behavior of GH3535 alloy induced by fission product Te

et al. 2022

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The effect of systematic variation of Ni:Co ratio on the oxidation behaviour of γ-γ′ Ni-Co-Al-Ti-Cr alloys

Cited by 7 publications

References 50 publications

The Effect of Nb, Ta, and Ti on the Oxidation of a New Polycrystalline Ni-Based Superalloy

The Effect of Nb, Ta, and Ti on the Oxidation of a New Polycrystalline Ni-Based Superalloy

Influence of the Co/Ni Ratio and Dendritic Segregations on the High-Temperature Oxidation Resistance of Multinary Co-Rich Superalloys at 850 °C and 1050 °C

Effect of Al addition on intergranular embrittlement behavior of GH3535 alloy induced by fission product Te

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