Thermophysical and Mechanical Properties of Advanced Single Crystalline Co-base Superalloys

Volz, Nicklas; Zenk, Christopher H.; Cherukuri, Ramachand; Kalfhaus, Tobias; Weiser, M.; Makineni, Surendra Kumar; Betzing, C.; Lenz, Malte; Gault, Baptiste; Fries, Suzana G.; Schreuer, J.; Vaßen, Robert; Virtanen, Sannakaisa; Raabe, Dierk; Spiecker, Erdmann; Neumeier, Steffen; Göken, Mathias

doi:10.1007/s11661-018-4705-1

“…The effect of Re addition to these alloys is limited [54,55]. Recent experimental and first-principles kinetic Monte Carlo studies by Neumeier et al show Re is the slowest diffusing element amongst all transition metals in fcc-Co [56].…”

Section: Introductionmentioning

confidence: 99%

“…Due to the higher vacancy formation energy in Co, the diffusivity and activation energy barrier of Re is greater than Ni [56,57]. However, Kolb et al [54] and Volz et al [55] showed Re addition to a single crystalline Co-Ni-Al-W based alloy leads to a marginal or no improvement in creep properties compared to the role of Re in the 2nd and 3rd generation Ni-Al based superalloys. This was attributed to the low partitioning of Re to the g matrix phase.…”

Section: Introductionmentioning

confidence: 99%

On the effect of Re addition on microstructural evolution of a CoNi-based superalloy

Pandey

¹

,

Sawant

²

,

Baler

³

et al. 2019

Self Cite

View full text Add to dashboard Cite

In this study, the effect of rhenium (Re) addition on microstructural evolution of a new low-density Co-Ni-Al-Mo-Nb based superalloy is presented. Addition of Re significantly influences the g 0 precipitate morphology, the g/g 0 lattice misfit and the g/g 0 microstructural stability during long term aging. An addition of 2 at.% Re to a Co-30Ni-10Al-5Mo-2Nb (all in at.%) alloy, aged at 900 C for 50 h, reduces the g/ g 0 lattice misfit by~40% (from þ0.32% to þ0.19%, measured at room temperature) and hence alters the g 0 morphology from cuboidal to round-cornered cuboidal precipitates. The composition profiles across the g/g 0 interface by atom probe tomography (APT) reveal Re partitions to the g phase (K Re ¼ 0:34Þ and also results in the partitioning reversal of Mo to the g phase (K Mo ¼ 0:90) from the g 0 precipitate. An inhomogeneous distribution of Gibbsian interfacial excess for the solute Re (G Re , ranging from 0.8 to 9.6 atom.nm À2) has been observed at the g/g 0 interface. A coarsening study at 900 C (up to 1000 h) suggests that the coarsening of g 0 precipitates occurs solely by evaporationecondensation (EC) mechanism. This is contrary to that observed in the Co-30Ni-10Al-5Mo-2Nb alloy as well as in some of the Ni-Al based and high mass density CoAl -W based superalloys, where g 0 precipitates coarsen by coagulation/coalescence mechanism with an extensive alignment of g 0 along <100> directions as a sign of microstructural instability. The g 0 coarsening rate constant ðK r Þ and g/g 0 interfacial energy are estimated to be 1.13 Â 10 À27 m 3 /s and 8.4 mJ/m 2 , which are comparable and lower than CoAl -W based superalloys.

show abstract

“…[14][15][16] Phase stability and high-temperature mechanical properties were significantly improved in the last years by addition of a wide range of alloying elements. [17][18][19][20][21] However, to assure long-term stability of these new superalloys in application, not only their mechanical properties but also their resistivity against oxidation have to be studied and improved. For the understanding of elementary (transport) mechanisms during scale growth on complex Co-base superalloys under oxidizing atmospheres, it is crucial to gain insight into the porosity, pore connectivity, as well as phase formation and further evolution upon exposure at elevated temperatures.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, research on oxidation of Co-base superalloys has attracted a lot of interest and considerable progress has been achieved by dedicated alloy design. [21][22][23][24][25] Since pores and phases of these complex multilayered oxide scales extend into 3D with both nanometer-and micrometersized features, a site-specific, scale-bridging, and 3D characterization approach is required. One commonly used technique is focused ion beam/scanning electron microscopy tomography (FIB/SEM tomography or, shortly, FIB tomography).…”

Section: Introductionmentioning

confidence: 99%

Correlative Nano‐Computed Tomography and Focused Ion‐Beam Sectioning: A Case Study on a Co‐Base Superalloy Oxide Scale

Lenz

¹

,

Wirth

²

,

Englisch

³

et al. 2019

View full text Add to dashboard Cite

Herein, the capabilities of a correlative tomography approach combining laboratory nano X‐ray computed tomography, focused ion‐beam sectioning, and energy‐dispersive X‐ray spectroscopy are utilized for the characterization of multilayered oxide scales of Co‐base superalloys regarding their 3D morphology and chemical composition. The combination of complementary 3D imaging techniques allows for a precise and reliable segmentation of the pore space, oxide precipitates, and different phases of the initial material. Such information is instrumental to a microscopic understanding of oxidation in this new class of superalloys and key to improvement of oxidation resistance in the next‐generation high‐temperature materials.

show abstract

“…The effect of Re addition to these alloys is limited [54,55]. Recent experimental and first principles kinetic Monte Carlo studies by Neumeier et al show Re is the slowest diffusing element amongst length, L-80 mm) under argon atmosphere using a split water-cooled copper mold in a vacuum suction casting unit.…”

Section: Introductionmentioning

confidence: 99%

On the Effect of Re Addition on Microstructural Evolution of a CoNi-Based Superalloy

Pandey

¹

,

Sawant

²

,

Baler

³

et al. 2018

SSRN Journal

0

View full text Add to dashboard Cite

In this study, the effect of rhenium (Re) addition on microstructural evolution of a new low-density Co-Ni-Al-Mo-Nb based superalloy is presented. Addition of Re significantly influences the γ' precipitate morphology, the γ/γ' lattice misfit and the γ/γ' microstructural stability during long termaging. An addition of 2 at.% Re to a Co-30Ni-10Al-5Mo-2Nb (all in at.%) alloy, aged at 900°C for 50 hours, reduces the γ/γ' lattice misfit by ~ 40% (from +0.32% to +0.19%, measured at room temperature) and hence alters the g' morphology from cuboidal to round-cornered cuboidal precipitates. The composition profiles across the γ/γ' interface by atom probe tomography (APT) reveals Re partitions to the g phase ( "# = 0.34) and also results in the partitioning reversal of Mo to the g phase ( *+ = 0.90) from the γ' precipitate. An inhomogeneous distribution of Gibbsian interfacial excess for the solute Re (Γ "# , ranging from 0.8 to 9.6 atom.nm -2 ) has been observed at the γ/γ' interface. A coarsening study at 900°C (up to 1000 hours) suggests that the coarsening of γ' precipitates occurs solely by an evaporation-condensation (EC) mechanism. This is contrary to that observed in the Co-30Ni-10Al-5Mo-2Nb alloy as well as in some of the Ni-Al based and high mass density Co-Al-W based superalloys, where γ' precipitates coarsen by coagulation/coalescence mechanism with extensive alignment of γ' along <100> directions as a sign of microstructural instability. The γ' coarsening rate exponent ( / ) and γ/γ' interfacial energy are estimated to be 1.41 ´ 10 -27 m 3 /s and 8.4 mJ/m 2 , which are comparable and lower than Co-Al-W based superalloys.Keywords: Rhenium (Re); Cobalt-based superalloys; Lattice misfit; Atom probe tomography (APT); Coarsening kinetics. all transition metals in fcc-Co [56]. Due to the higher vacancy formation energy in Co, the diffusivity and activation energy barrier of Re is greater than Ni [56,57]. However, Kolb et al. [54] and Volz et al. [55] showed Re addition to a single crystalline Co-Ni-Al-W based alloy leads to a marginal or no improvement in creep properties compared to the role of Re in the 2 nd and 3 rd generation Ni-Al based superalloys. This was attributed to the low partitioning of Re to the γ matrix phase. Hence, it was concluded that Re is not crucial for Co-Al-W based superalloys.The addition of Re could have an important role for the long term microstructural stability of Co-Al based superalloys. However, the role of Re in the coarsening behavior of cobalt based alloys, in particular that of the low-density Co-Al-Mo-Nb/Ta based superalloys, has not been explored rigorously. Some studies on the kinetics and associated models have been reported for Re added Ni-Al based superalloys [27,28,58]. They show that the coarsening of precipitates follows Lifshitz-Slyozov-Wagner (LSW) based Ostwald ripening mechanism with slight variation in temporal exponents.The present work reports a detailed study on the effect of Re addition on a low density W-free g/g¢ Co-Al based superalloys. Microstructural evolut...

show abstract

Thermophysical and Mechanical Properties of Advanced Single Crystalline Co-base Superalloys

Cited by 65 publications

References 61 publications

On the effect of Re addition on microstructural evolution of a CoNi-based superalloy

On the effect of Re addition on microstructural evolution of a CoNi-based superalloy

Correlative Nano‐Computed Tomography and Focused Ion‐Beam Sectioning: A Case Study on a Co‐Base Superalloy Oxide Scale

On the Effect of Re Addition on Microstructural Evolution of a CoNi-Based Superalloy

Contact Info

Product

Resources

About