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

Published

August 17, 2024

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

Pub Type

Journals

Download Paper

https://doi.org/10.1016/j.msea.2024.147105

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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 October 20, 2025)