An Atom-Probe Study of Some Fine-Scale Microstructural Features in Ni-Based Single Crystal Superalloys

Abstract

Some fine-scale microstructure of nickel-based single crystal superalloys have been investigated by means of atom probe techniques.

What is the role of rhenium in single crystal superalloys?

“…It is arguable whether this is evidence for either short range ordering or clustering of Re atoms in the γ phase of Ni-based superalloys. The authors proposed the evidence collected proved the presence of Re clusters, 1-1.5 nm in size, that contained up to 90 at.% Re [4,19], suggesting this would be expected when considering the large miscibility gap in the established Ni-Re binary phase diagram [20,21]. It follows that these clusters would act as powerful barriers against dislocation glide when compared to distributed Re atoms in solid solution with Ni.…”

“…Blavette and co-workers pioneered the use of atom probe analysis to study the behaviour of Re in Ni-based superalloys [4,19]. In this work, the one-dimensional version of the tool (1DAP) was used to examine the solute distribution in PWA 1480, CMSX-2, PWA 1480-Re (with a nominal 4 wt.% Re and no W) and CMSX-2-4Re (containing 4 wt.% Re and 4 wt.% W).…”

“…Investigation of the Ni-Re 0 K formation energy hull indicates that Ni 4 Re (D1 a ) and NiRe 3 (D0 19 ) should be stable at absolute zero [31,32]. High-throughput DFT calculations were also used to parameterise a cluster expansion to determine the effect of configurational entropy on the free energy of the relevant phases through a Monte Carlo approach [31,33].…”

Microstructure Evolution in the Nickel Base Superalloy Allvac 718Plus®

“…It is also possible to determine the mole fraction of the γ′-precipitate phase from the chemical composition of the phases γ and γ′ and the overall alloy composition. The method employed here is known as the Blavette method or lever rule [ 12 ]. This method is useful as the reliable determination of the γ′-volume fraction from TEM-or SEM-micrographs is difficult due to the small size of the γ′-particles in 718Plus.…”

The Effect of Composition, Misfit, and Heat Treatment on the Primary Creep Behavior of Single Crystal Nickel Base Superalloys PWA 1480 and PWA 1484

“…Lattice misfit, stacking fault energy, and anti-phase boundary energy can all be impacted by various elemental additions. Rhenium, in particular, may also be linked to primary creep because of the number of second generation alloys that display this behavior despite accounts of Re segregating almost exclusively to the γ phase [16,17]. In alloys containing tungsten, however, as much as 20% of the Re added to the alloy has been shown to partition to the γ' [18].…”