Thermal stability of advanced Ni-base superalloys

Tawancy, H. M.; Abbas, Nureddin M.; Al-Mana, A.I.; Rhys-Jones, T.N.

doi:10.1007/bf00363439

Cited by 35 publications

(14 citation statements)

References 12 publications

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“…[1,2,6,8] In the present alloys, the SEM and EDS analyses of the leading edge of blade 1 (Figure 7) indicate that the MC decomposition results in its breaking up into several smaller zones. Specifically, the degenerated MC is surrounded by a well-defined decomposition zone, with numerous discrete precipitates formed on its periphery (Figures 7(a) and (b)).…”

Section: Primary MC Decompositionmentioning

confidence: 98%

“…All three blades display significant changes in the leading edge microstructures compared to those of the shank; this is typical of service-exposed gas turbine blades. [1][2][3][4][5][6][7][8]11] The micrographs of all three blades displayed similar features of severe overaging, regardless of the chemical composition and grain size. First, the primary ␥Ј precipitates coalesced and coarsened considerably.…”

Section: B Leading Edge Specimensmentioning

confidence: 99%

“…These microstructural modifications usually lead to a degradation of mechanical properties, such as tensile strength and creep resistance. Extensive studies have shown that prolonged thermal and stress exposure causes "overaging" of the microstructure (␥Ј coarsening and coalescence, formation of secondary M 23 C 6 precipitates on the grain boundaries (GB) [1][2][3][4][5] primary MC degeneration, [5,6,7] and topologically close-packed (TCP) phase (e.g., -phase) formation, [1][2][3][4][5][6] ) all of which are detrimental to both tensile strength and creep resistance.…”

Section: Modern Industrial Gas Turbine Blades Made Frommentioning

confidence: 99%

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Mechanism of primary MC carbide decomposition in Ni-base superalloys

Lvov¹,

Levit²,

Kaufman

2004

Metall Mater Trans A

188

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Three industrial gas turbine blades made of conventionally cast (CC) IN-738 and GTD-111 and directionally solidified GTD-111 Ni-base superalloys were examined after long-term exposures in service environments. All three blades exhibit similar, service-induced microstructural changes (MCs) including ␥Ј coarsening and coalescence, excessive secondary M 23 C 6 precipitation, and primary MC degeneration, regardless of the chemical composition and the grain size. Special attention was paid to the primary MC decomposition. It is shown that the primary MC decomposition occurs by carbon diffusion out of the carbide into the ␥ ϩ ␥Ј matrix, resulting in the formation of Cr-rich M 23 C 6 carbides near the initial carbide/matrix interface. A transition zone is shown to develop between the original MC core and its perimeter, demonstrating the gradual outward diffusion of carbon and a slight inward increase in nickel concentration. The hexagonal Ni 3 (TiTa) -phase was also found in the MC transition zone and on the MC-␥/␥Ј interface. The primary MC decomposition can be expressed by the reaction MC ϩ ␥ր␥Ј → M 23 C 6 ϩ . Finally, it is shown that the grain-boundary (GB) MC decomposes more rapidly than that in the grain interiors. This is consistent with the more rapid GB diffusion that leads to the acceleration of the MC diffusional decomposition processes.

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Section: Primary MC Decompositionmentioning

confidence: 98%

Section: B Leading Edge Specimensmentioning

confidence: 99%

Section: Modern Industrial Gas Turbine Blades Made Frommentioning

confidence: 99%

See 1 more Smart Citation

Mechanism of primary MC carbide decomposition in Ni-base superalloys

Lvov¹,

Levit²,

Kaufman

2004

Metall Mater Trans A

188

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“…3c. As can be seen, it contains a higher concentration of W in comparison with the surface layer of γ′ (Table 2) similar to the case of γ′-phase, which solidifies from the melt during casting of superalloys and assumes a lamellar morphology [37].…”

Section: Resultsmentioning

confidence: 79%

On the performance and failure mechanism of thermal barrier coating systems used in gas turbine blade applications: Influence of bond coat/superalloy combination

Tawancy

Mohammad

Al‐Hadhrami

et al. 2015

Engineering Failure Analysis

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“…Below the original superalloy surface, the c 0 -phase of both bond coats is observed to assume blocky lamellar morphology resembling the primary c 0 -phase which solidifies from the melt in cast superalloys and contains high concentration of refractory transition metals particularly W [14,15]. It is noted that although both W and Ta tend to partition to the c 0 -phase by occupying Al sublattice sites, it is found that the respective amount of W increases with decreasing the Ta content and vice versa [16,17].…”

Section: Resultsmentioning

confidence: 98%

Enhancing the Oxidation Properties of Gamma Prime + Gamma Platinum Bond Coat by Rhenium and Yttrium Additions for Improved Adhesion of Thermal Barrier Coatings on Nickel-Base Superalloys

Tawancy

2015

Oxid Met

Self Cite

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A Re-and Y-modified c 0 ? c Pt bond coat was synthesized by diffusing 25 lm layer of Ni-6 wt%Re-0.5 wt%Y alloy and 5 lm layer of Pt into a Ni-based superalloy. It was observed that the modified bond coat can extend the useful life of thermal barrier coating systems with yttria-stabilized zirconia as top coat by more than double relative to the conventional bond coat synthesized by diffusing 8 lm layer of Pt into the same superalloy. The superior performance of the modified bond coat is explained in terms of the combined beneficial effects of Re and Y on the oxidation properties as determined from thermal exposure tests at 1150°C and detailed microstructural characterization using various electron-optical techniques.

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Thermal stability of advanced Ni-base superalloys

Cited by 35 publications

References 12 publications

Mechanism of primary MC carbide decomposition in Ni-base superalloys

Mechanism of primary MC carbide decomposition in Ni-base superalloys

On the performance and failure mechanism of thermal barrier coating systems used in gas turbine blade applications: Influence of bond coat/superalloy combination

Enhancing the Oxidation Properties of Gamma Prime + Gamma Platinum Bond Coat by Rhenium and Yttrium Additions for Improved Adhesion of Thermal Barrier Coatings on Nickel-Base Superalloys

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