HRTEM analysis of the high-temperature phases of the newly developed high-temperature Ni-base superalloy VDM 780 Premium

Ghica, C.; Solís, Cecilia; Munke, Johannes; Stark, Andreas; Gehrmann, Bodo; Bergner, M.; Rösler, Joachim; Gilles, Ralph

doi:10.1016/j.jallcom.2019.152157

Cited by 22 publications

(12 citation statements)

References 33 publications

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“…This is so because the major reflections of both phases are very close, while the minor reflections are hard to detect given the relatively small amount of δ/η in the alloy. First TEM investigations on a small number of particles demonstrated the simultaneous presence of δ and η within one particle [41]. This fits to the observation made earlier in conjunction with Figure 6e and it appears likely that both phases coexist not only in VDM Alloy 780 but also in the model alloys studied here.…”

Section: The Effect Of the Al/ti Ratiosupporting

confidence: 91%

On the Development Concept for a New 718-Type Superalloy with Improved Temperature Capability

Rösler

Hentrich²,

Gehrmann³

2019

Metals

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The superalloy 718 stands out for its excellent manufacturability and strength at ambient temperature. However, its application temperature is limited to about 650 °C due to the instability of the γ’’ precipitates. Here, we provide an in-depth account of an alloy development concept, allowing for the design of superalloys with 718-type properties, yet with a significantly improved microstructural stability. The article begins with a detailed discussion on how the microstructural and chemical composition must be altered to achieve this objective. Then, model alloys were used to explore and validate the outlined strategy. Finally, it is shown how these considerations ultimately led to a new 718-type superalloy with far more improved microstructural stability— namely, VDM Alloy 780. The introduction of a large amount of Co as a substitute for Fe (and partially Ni) is the most important element of our alloy development concept in terms of chemical composition. The most important microstructural feature is the introduction of low solvus temperature, high misfit γ´-strengthening, replacing γ´´-hardening.

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Section: The Effect Of the Al/ti Ratiosupporting

confidence: 91%

On the Development Concept for a New 718-Type Superalloy with Improved Temperature Capability

Rösler

Hentrich²,

Gehrmann³

2019

Metals

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“…In [8,21,22], a new Nb-containing wrought superalloy was developed. In this context, it was found that Co-addition increases the solvus temperature of the Nb-rich high temperature precipitates that were identified to consist of η-and δ-phase [23].…”

Section: Discussionmentioning

confidence: 99%

Effect of Co and Cr on the Stability of Strengthening Phases in Nickelbase Superalloys

Bäker¹,

Rösler²

2022

Preprint

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Nickel-base superalloys like VDM 780 may possess a high content of Cr and Co. This influences solution energies of phase-forming elements like Al and Ta (γ′-phase), Nb (γ′′- and δ-phase), and Ti (η-phase). We perform density functional theory studies of a nickel matrix at 0 K with high concentrations of either Co and Cr and calculate the influence of these elements on solution energies. In the case of Co, the solution energy can be predicted well by the nearest-neighbor interaction in the Co-rich matrix. For Cr, the effect is more complicated because Cr has a larger ionic radius and changes the magnetic state of the material. The effect of a Cr-rich matrix on the energy of Co is dominated by magnetic effects, interactions with the other elements by elastic deformation of the lattice.

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“…The microstructure at the room and elevated temperature of VDM 780 has already been investigated in previous publications by the authors of this paper by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) as well as ND and SANS [26][27][28]. The microstructure consists of γ-matrix, hardening γ -phase, and high temperature stable δand η-phases.…”

Section: Introductionmentioning

confidence: 86%

Deformation Mechanisms in Ni-Based Superalloys at Room and Elevated Temperatures Studied by In Situ Neutron Diffraction and Electron Microscopy

Kümmel

Kirchmayer

Solís

et al. 2021

Metals

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Polycrystalline Ni-based superalloys are one of the most frequently used materials for high temperature load-bearing applications due to their superior mechanical strength and chemical resistance. In this paper, we presented an in situ diffraction study on the tensile deformation behavior of the polycrystalline Ni-based superalloy VDM® Alloy 780 at temperatures up to 500 °C performed at the STRESS-SPEC neutron diffractometer at the Heinz Maier-Leibnitz Zentrum. A detailed microstructural investigation was carried out by electron microscopy before and after testing. The results of these studies allowed us to determine the deformation mechanism in the differently orientated grains. It is shown that the deformation behavior, which is mainly dislocation motion and shearing of the γ′-precipitates, does not change at this temperature range. The deformation is strongly anisotropic and depends on the grain orientation. The macroscopic hardening can mainly be attributed to plastic deformation in grains, where the (200) lattice planes were orientated perpendicular to the loading direction. Accordingly, a remaining lattice strain and high dislocation density were detected predominantly in these grains.

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HRTEM analysis of the high-temperature phases of the newly developed high-temperature Ni-base superalloy VDM 780 Premium

Cited by 22 publications

References 33 publications

On the Development Concept for a New 718-Type Superalloy with Improved Temperature Capability

On the Development Concept for a New 718-Type Superalloy with Improved Temperature Capability

Effect of Co and Cr on the Stability of Strengthening Phases in Nickelbase Superalloys

Deformation Mechanisms in Ni-Based Superalloys at Room and Elevated Temperatures Studied by In Situ Neutron Diffraction and Electron Microscopy

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