Influence of coatings and hot corrosion on the fatigue behaviour of nickel-based superalloys

Schneider, Klaus; Arnim, H. von; Grünling, H.W.

doi:10.1016/0040-6090(81)90006-7

Cited by 55 publications

(16 citation statements)

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“…Note that, when the coating can share or carry an external load equally to the superalloy substrate, the values of the vertical axis for the coated specimens can be decreased in maximum by the area ratio of coating (about 20 pct), although MCrAlY alloys are generally not supposed to have such ability, at least at the test temperature in this work (i.e., of 950°C). [17,18] From Figure 4, it is found that the fatigue lives of the coated specimens are generally longer than those of the corresponding bare specimens. Comparing the difference of fatigue strength between the No-Cell/X and No-Cell/bare specimens, the magnitude of the improvement by the coating is almost comparable to, or more than, the above order of ambiguity in stress amplitude.…”

Section: B a Trial To Prevent The Undesirable Effect Due To Cellularmentioning

confidence: 99%

Damage repair in CMSX-4 alloy without fatigue life reduction penalty

Okazaki

Ohtera

Harada

2004

Metall Mater Trans A

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The microstructural changes in a single-crystal Ni-base superalloy, CMSX-4, that might occur during the processes of repair and recoating of hot section components for advanced gas turbines were studied. It is shown that the cellular ␥/␥Ј microstructure is formed when the material is subjected to local plastic straining, followed by the reheat treatments during the course of damage recovery. The formation of cellular microstructure in the material led to the remarkably reduced fatigue strength. In order to reduce or prevent the preceding undesirable effect resulting from cellular microstructure, a new method based on applying overlay coating technique was developed. The method is based on an idea that the alloying elements that are depleted in base alloys could be supplemented via the overlay coating. An X alloy, which contains grain boundary strengthening elements, was selected and coated on the CMSX-4 with the cellular microstructure by low-pressure plasma spraying. The fatigue tests on the coated CMSX-4 specimens demonstrated the effectiveness of the method. The observations of the crack initiation site, the fatigue fracture mode, the crack density in the cellular transformed area, and the crack propagation morphologies near the prior interface strongly supported the validity of this approach. The method is expected to build a road to a so-called damage cure (or recovery) coating.

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Section: B a Trial To Prevent The Undesirable Effect Due To Cellularmentioning

confidence: 99%

Damage repair in CMSX-4 alloy without fatigue life reduction penalty

Okazaki

Ohtera

Harada

2004

Metall Mater Trans A

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“…Usually a thin layer of Pt is electroplated on the substrate alloy, and then aluminized. This modi®cation was aimed to improve the hot-corrosion resistance and adhesion strength [14,15]. Application of steam cooling in advanced gas turbines enhances this kind of protective coatings inside the components.…”

Section: History Of Protective Coatingsmentioning

confidence: 99%

High-temperature strength of Ni-base superalloy coatings

Okazaki

2001

Science and Technology of Advanced Materials

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Recently considerable attention has been paid to large utility gas turbines, because of their high ef®ciency and many other advantages. This accelerates the introduction of advanced superalloys and coatings. While these technologies are traditionally from aero turbines, many novel challenges have arisen in their application, e.g. long operating time, weight, cyclic duty, environment using cheaper fuel, and size. This paper describes the mechanical properties and failures of the superalloys and the coatings used at the hot sections of utility gas turbines. Special focus is put on thermo-mechanical fatigue failure, and the collaborative test results by the Subcommittee of ªSuperalloys and Coatingsº in The

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“…Strain-controlled isothermal LCF tests at conventionally cast Ni-Superalloys typically show large fatigue lifetime scatter up to a factor of 10, even in the LCF regime [5][6][7][8][9]. A major reason for this are orientation dependent resolved shear stresses in the randomly oriented coarse grains.…”

Section: Introductionmentioning

confidence: 99%

Effect of local anisotropy on fatigue crack initiation in a coarse grained nickel-base superalloy

et al. 2018

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Abstract. In the present work, theoretical approaches, based on grain orientation dependent Young's modulus and Schmid factor are used to describe the influence of local grain orientation on crack initiation behaviour of the coarse grained nickel base superalloy René80. Especially for strongly anisotropic crystal structures with large grain size, such as the investigated material, the local elastic properties must be taken into account for assessment of fatigue crack initiation. With an extension of Schmid's law, the resulting shear stress amplitude, which triggers local cyclic plastic deformation, can be calculated depending on local Young`s modulus and Schmid factor. A Monte Carlo simulation with 100,000 samples shows how random grain orientation affects these parameters. Furthermore, the product of Young`s modulus and Schmid factor (called E•m) is used as a parameter to determine how grain orientation influences resulting shear stress amplitude for given total strain amplitude. In addition to the theoretical work using that approach, this model is also validated using isothermal LCF experiments by determining local grain orientation influence on the crack initiation site using SEM-EBSD analyses.

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Influence of coatings and hot corrosion on the fatigue behaviour of nickel-based superalloys

Cited by 55 publications

References 0 publications

Damage repair in CMSX-4 alloy without fatigue life reduction penalty

Damage repair in CMSX-4 alloy without fatigue life reduction penalty

High-temperature strength of Ni-base superalloy coatings

Effect of local anisotropy on fatigue crack initiation in a coarse grained nickel-base superalloy

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