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Microstructure and Properties of Co-Ni-Al-W Gamma/Gamma Prime Superalloy Fabricated via Laser Fusion of Elemental Powders

Published

Author(s)

Hyeji Im, Júlio Cesar Pereira Dos Santos, Carelyn E. Campbell, David Dunand

Abstract

Ball-milled elemental Co, Ni, Al, and W powders were used to fabricate a Co-0.20Ni-0.11Al-0.08W (mole fraction) alloy via laser powder bed fusion (L-PBF). In the as-fused state, microstructural features present within the FCC-γ Co-Ni-Al-W matrix – partially-melted W powders, W-deficient regions, and cracks – are investigated with respect to the laser scanning speed. Tungsten particles appear to block or deflect internal cracks, thus improving cracking resistance due to thermal cycling during laser fusion. However, W-deficient regions, which are also enriched with Ni and Al, can act as crack nucleation sites due to the brittleness of the β-NiAl and eutectic microconstituents. A homogenous FCC-γ Co-0.20Ni-0.11Al-0.08W (mole fraction) solid solution is obtained after a solutionizing treatment at 1200 ºC, as W-rich particles fully dissolve, and W-deficient regions homogenize, into the matrix. A γ/γ'-two-phase microstructure forms upon subsequent aging at 900 ºC, whose creep resistance is measured at 850 °C: below 300 MPa, deformation is dominated by diffusional creep (consistent with a relatively fine grain size of 50 μm to 100 μm) while above 300 MPa, it is controlled by dislocation creep. Using elemental powder blends is a viable method to create microstructurally-sound, creep-resistant Co-based γ/γ' superalloys via L-PBF.
Citation
Additive Manufacturing

Keywords

Co-based superalloy, selective laser melting, microstructure, cracking, creep resistance

Citation

Im, H. , Pereira Dos Santos, J. , Campbell, C. and Dunand, D. (2023), Microstructure and Properties of Co-Ni-Al-W Gamma/Gamma Prime Superalloy Fabricated via Laser Fusion of Elemental Powders, Additive Manufacturing, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=936789 (Accessed April 23, 2024)
Created August 8, 2023, Updated March 11, 2024