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

Kümmel, Frank; Kirchmayer, Andreas; Solís, Cecilia; Hofmann, M.; Neumeier, Steffen; Gilles, Ralph

doi:10.3390/met11050719

Cited by 9 publications

(2 citation statements)

References 53 publications

(75 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The microstructure of the VDM ® Alloy 780 was previously intensively investigated by the authors by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM), as well as neutron diffraction (ND) and small-angle neutron scattering (SANS) [25][26][27][28]. The microstructure consists of the γ-matrix, the γ -hardening phase, and the δ-, η-, and Nb/Mo-based high-temperature-stable carbide phases (hereinafter denoted as NbC, for clarity).…”

Section: Introductionmentioning

confidence: 99%

Near-Surface and Bulk Dissolution Behavior of γ′ Precipitates in Nickel-Based VDM® Alloy 780 Studied with In-Situ Lab-Source and Synchrotron X-ray Diffraction

Kümmel

Fritton

Solís

et al. 2022

Metals

Self Cite

View full text Add to dashboard Cite

The dissolution of nano-sized Ni3Al-based γ′ precipitates was investigated in the newly developed polycrystalline nickel-based VDM® Alloy 780 at the surface and in the bulk region with in-situ lab-source and synchrotron X-ray diffraction. These studies are important in obtaining a deeper understanding of the strengthening mechanism responsible for the stability and long service lives of such superalloys. We found that the dissolution behavior of the γ′ phase is very similar at the surface and in the bulk region, but small deviations were detected. The dissolution of γ′ starts at around 800 °C and no γ′ was found at temperatures exceeding 970 °C. As a result, the elements Al and Nb, which were bound in the γ′ phase, dissolved into the γ matrix and strongly increased the γ lattice parameter, as their atomic size is larger than the γ-forming elements Ni, Co, and Cr. However, this effect was suppressed in the surface area. A second matrix γ phase was detected at the same temperature range as that of the dissolution of the γ′ phase in the lab-source XRD measurements. The newly formed γ-2 phase had a smaller lattice parameter than that of the initial γ matrix. We propose that the γ-2 matrix phase is a result of high-temperature surface oxidation, which consumes, among other elements, Al and Nb and, therefore, leads to the smaller γ lattice parameter.

show abstract

Section: Introductionmentioning

confidence: 99%

Near-Surface and Bulk Dissolution Behavior of γ′ Precipitates in Nickel-Based VDM® Alloy 780 Studied with In-Situ Lab-Source and Synchrotron X-ray Diffraction

Kümmel

Fritton

Solís

et al. 2022

Metals

Self Cite

View full text Add to dashboard Cite

show abstract

“…Similarly, VDM Metals recently developed the VDM ® Alloy 780 to obtain a comparable forging window to that of Inconel 718 (IN718), but with superior microstructural stability, which allows significantly higher service temperatures [7,8]. VDM ® Alloy 780 shows a high tensile strength at room temperature and it has excellent mechanical strength at elevated temperatures [9].…”

Section: Introductionmentioning

confidence: 99%

Cracking during High-Temperature Deformation of a High-Strength Polycrystalline CoNi-Base Superalloy

Hausmann

Freund

Solís

et al. 2022

Metals

Self Cite

View full text Add to dashboard Cite

The crack susceptibility during processing has a crucial influence on the workability of wrought alloys. In particular, the processing of high-strength alloys that are prone to cracking is challenging and various process parameters have to be optimized to achieve a good formability. The polycrystalline CoNi-base superalloy CoWAlloy1 provides a high potential for high-temperature applications due to it having a large forging window, a high γ′ fraction and excellent creep properties. In order to study its formability during hot rolling, its deformation behavior and susceptibility to cracking were characterized by sub- and supersolvus compression tests at temperatures between 1000–1150 °C. At temperatures around the γ′ solvus temperature, no cracks formed during the compression testing, while at lower temperatures, cracking occurred. Additionally, an in-situ high-temperature small-angle neutron scattering revealed the phase fractions and the precipitate size distributions at different processing temperatures. It was found that a high fraction of γ′ forms during cooling and cracking starts at the surface of the bar, when the hot bar encounters the cold rolls during hot rolling. Apparently, the precipitation of γ′, which causes a high strength and reduced ductility, and the absent recrystallization leads to pronounced crack propagation and limited formability below the γ′ solvus temperature.

show abstract

Investigation of the Hot Deformation Behavior in VDM® Alloy 780 by In Situ High-Energy X-Ray Diffraction

Fritton

Kümmel

Kirchmayer

et al. 2023

Metall Mater Trans A

Self Cite

View full text Add to dashboard Cite

Ni-based superalloys are indispensable for applications in demanding environments, such as the heavily stressed rotating discs in the hot sections of modern gas turbines or jet engines. In this paper, the microstructure evolution during hot deformation to mimic the forging process was investigated in the polycrystalline VDM® Alloy 780 viain situ X-ray diffraction at temperatures of 950, 1000, and 1050 °C. For the tested temperatures, the hot forming led to subgrain formation, the built-up of a texture by rotation of the matrix grains into preferred orientations, and dynamic recrystallization. The influence of the deformation was analyzed depending on the direction of the lattice plane normals to the load direction, for the first five γ-reflections in the diffraction pattern. During uniaxial compressive deformation intensity, maxima develop in the loading direction solely for the γ-(220) reflections, while intensity minima develop for the other reflections which correspond to the formation of a <110> fiber texture. In the transverse direction, all γ-reflections except the (220) have an increased intensity at the maximum specimen strain of 20 pct. Directly after the hot forming, three different cooling rates of 10, 100, and 1000 °C/min and their influence on the microstructure were investigated. The fast and medium cooling rates lead to low recrystallized fractions and a largely preserved deformation texture, whereas the low cooling rate leads to a high recrystallized fraction and a slight remaining texture. Additionally, the diffraction data are complemented by electron microscopy measurements.

show abstract

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

Cited by 9 publications

References 53 publications

Near-Surface and Bulk Dissolution Behavior of γ′ Precipitates in Nickel-Based VDM® Alloy 780 Studied with In-Situ Lab-Source and Synchrotron X-ray Diffraction

Near-Surface and Bulk Dissolution Behavior of γ′ Precipitates in Nickel-Based VDM® Alloy 780 Studied with In-Situ Lab-Source and Synchrotron X-ray Diffraction

Cracking during High-Temperature Deformation of a High-Strength Polycrystalline CoNi-Base Superalloy

Investigation of the Hot Deformation Behavior in VDM® Alloy 780 by In Situ High-Energy X-Ray Diffraction

Contact Info

Product

Resources

About