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Co-Ni-Al-W gamma/gamma prime Superalloy with Cr and Ti additions Fabricated via Laser Fusion of Elemental Powders

Published

Author(s)

Hye Ji Im, Júlio Cesar Pereira Dos Santos, Carelyn Campbell, David Dunand

Abstract

A Co-based superalloy (Co-0.20Ni-0.11Al-0.07W-0.04Cr-0.03Ti, mole fraction) was synthesized by laser powder-bed fusion of a blend of elemental powders. The as-built alloy shows a γ-FCC matrix where the high-melting Ti and Cr powders are fully dissolved, but the refractory W particles are only partially melted. Full dissolution of the W particles is achieved after homogenization at 1150 °C, resulting in a homogeneous, single-phase γ microstructure. Upon aging at 900 ºC, a two-phase γ/γ′ microstructure forms, with a high-volume fraction of sub-micron γ' precipitates with cuboidal shape. Compared to a control quaternary alloy without Cr and Ti fabricated by the same method, the present alloy has increased γ' fraction and microhardness after aging for 300 h, maintaining a strong γ' strengthening effect without forming γ'-depleted zone at grain boundaries. Micron-size γ'-precipitates at grain boundaries also shift the transition between diffusional and dislocation creep to lower stress levels, by inhibiting diffusional creep and grain-boundary sliding. However, overall creep resistance is lowered, consistent with a reduction of lattice mismatch due to Cr additions and rafting of γ' precipitates. Furthermore, Cr and Ti additions improve oxidation resistance at 900 ºC, due to the formation of a continuous Cr-, Ti- and Al-rich oxide layer.
Citation
Materials Science and Engineering A

Keywords

Co-based superalloy, selective laser melting, microstructure, creep, oxidation

Citation

Im, H. , Pereira Dos Santos, J. , Campbell, C. and Dunand, D. (2024), Co-Ni-Al-W gamma/gamma prime Superalloy with Cr and Ti additions Fabricated via Laser Fusion of Elemental Powders, Materials Science and Engineering A, [online], https://doi.org/10.1016/j.msea.2024.147105, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=957664 (Accessed February 18, 2025)

Issues

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Created August 17, 2024, Updated January 22, 2025