Screening for Al2O3 failure in MCrAlY APS coatings using short-term oxidation at high temperature

Texier, Damien; Ecochard, Maxime; Gheno, Thomas; Monceau, Daniel; Salem, Mehdi; Lours, Philippe

doi:10.1016/j.corsci.2021.109334

Cited by 18 publications

(15 citation statements)

References 61 publications

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“…Alumina failure on MCrAlY coatings has been observed [21,22] but so far, detailed examinations of alloy and scale composition in pre-and post-failure stages have mostly concerned single-phase alloys. Recently, InCF has been studied in thin freestanding specimens of a multiphase APS NiCoCrAlY coating [23]. The reaction kinetics in Ref.…”

Section: Introductionmentioning

confidence: 99%

“…The reaction kinetics in Ref. [23] were affected by metallurgical defects inherent to the projection process. The aim of the present paper is to provide a more quantitative analysis of alloy composition variations and phase transformations in response to oxidation, and a more systematic description of the time-to-failure and post-failure reaction mechanisms in the NiCoCrAlY alloy system.…”

Section: Introductionmentioning

confidence: 99%

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Alumina Failure and Post-failure Oxidation in the NiCoCrAlY Alloy System at High Temperature

et al. 2021

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This paper examines the oxidation behavior of thin specimens of cast NiCoCrAlY alloys at 1150 • C through successive stages, from Al 2 O 3 growth to complete alloy conversion to oxide. Five alloy compositions were used, with varying fractions and compositions of γ and β. The time evolution of the alloy composition during Al 2 O 3 growth was simulated using the DICTRA module of Thermo-Calc, and calculated analytically in the approximation of flat profiles. Simulated and experimental profiles were found to be in good agreement, indicating that the phase equilibrium and mass balance were correctly reproduced in the simulations. Local variations of alloy composition were observed in thinner specimens and found to be comparable with the variations expected from the uncertainty on the initial specimen thickness. The variations observed in the time-to-Al 2 O 3 failure were greater than expected on this basis, suggesting that additional sources of variability were in effect. Alumina failure was followed by the growth of a Cr 2 O 3 layer at the alloy-scale interface. Similarly, Cr consumption eventually led to Cr 2 O 3 failure, and Ni-and Co-containing spinel oxide formed, converting the Cr 2 O 3 at the alloy-scale interface and the Al 2 O 3 at the scale-gas interface. The remaining NiCo alloy was then converted to (Ni,Co)O. This sequence occurred without abrupt increase of the mass gain, due to the continued presence of the remnant Al 2 O 3 layer, and to the small amount of metal left to oxidize when the (Ni,Co)O eventually broke through the scale. The evolution of the scale composition throughout the oxidation stages is discussed based on an analysis of the thermodynamic conditions at the alloy-scale interface.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Alumina Failure and Post-failure Oxidation in the NiCoCrAlY Alloy System at High Temperature

et al. 2021

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“…However, these projected coatings are much more prone to internal defects such as unmelted particles, pores, internal oxides and/or nitrides, intersplats. Oxygen ingress along these open channels causes oxide intrusions within the coating [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31]. This oxide intrusion, concomitant to external oxide scale growth, participates in the Al consumption.…”

Section: Introductionmentioning

confidence: 99%

“…The formation of the Al 2 O 3 scale and intrusions, together with the interdiffusion with the substrate, causes aluminum depletion in the coating. In thin products, this may bring the Al concentration down to a critical level where Al 2 O 3 is no longer stable [30,[32][33][34][35][36][37][38][39]. Other oxides may then form at the oxide/gas and metal/oxide interfaces on large regions.…”

Section: Introductionmentioning

confidence: 99%

Size effects on high temperature oxidation of MCrAlY coatings processed via APS and HVOF depositions

Kalush

Texier

Ecochard

et al. 2022

Surface and Coatings Technology

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“…The influence of the surface reactivity on the tensile properties of thin microtensile specimens is to be addressed [6]. Scaling approach using ultrathin specimens aims to echo the long-term exposure conditions needed to activate breakaway on conventional size specimens for very short exposures times, thanks to the limited amount of alloying elements [7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Oxidation of Thin Nickel-Based Superalloy Specimens: Kinetics Study and Mechanical Integrity

Romain

Texier

Desgranges³

et al. 2021

Oxid Met

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The oxidation behavior of a nickel-based superalloy was investigated from 650 to 1,000 °C for up to 1,000 h in air. Samples with thicknesses ranging from 20 to 500 µm were used to document the evolutions of microstructure and oxide scale. Oxidation products and subsurface evolution of the metal microstructure were characterized by XRD and EDS analyses. Local breakaway was observed after 600 h at 800 °C and after 100 h at 900 °C due to the full consumption of Cr from the alloy. Room temperature tensile tests were performed on aged and pre-oxidized specimens with thicknesses ranging from 20 µm to 500 µm, at 800 °C. The results were compared to tensile tests performed on the as-received metallurgical state. Both size effects due to sample thickness reduction and to sample thickness/pre-oxidation width ratio were examined onto the mechanical behavior. Interestingly, the formation of TCP phases, the oxide layer and the subsequent Cr-depleted subsurface region from either aging or oxidation treatments impairs the mechanical integrity. Bulk and subsurface regions are impacted, especially for tens-of-micrometer thin samples. KeywordsNickel-based superalloys • High-temperature oxidation • Breakaway • Gradient of microstructure and properties • Microtensile testing

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Screening for Al2O3 failure in MCrAlY APS coatings using short-term oxidation at high temperature

Cited by 18 publications

References 61 publications

Alumina Failure and Post-failure Oxidation in the NiCoCrAlY Alloy System at High Temperature

Alumina Failure and Post-failure Oxidation in the NiCoCrAlY Alloy System at High Temperature

Size effects on high temperature oxidation of MCrAlY coatings processed via APS and HVOF depositions

Oxidation of Thin Nickel-Based Superalloy Specimens: Kinetics Study and Mechanical Integrity

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