Fluidization behavior of graphitized glassy particles in a fluidized carbon bed cooling process for investment casting--颗粒学报PARTICUOLOGY

Git, P., Hofmeister, M., Singer, R. F., & Körner, C. (2022). Fluidization behavior of graphitized glassy particles in a fluidized carbon bed cooling process for investment casting. Particuology, 65, 32-38. https://doi.org/10.1016/j.partic.2021.07.001

Fluidization behavior of graphitized glassy particles in a fluidized carbon bed cooling process for investment casting

Paul Git ^*, Matthias Hofmeister, Robert F. Singer, Carolin Körner

Chair of Materials Science and Engineering for Metals (WTM), Friedrich-Alexander Universität, Erlangen-Nürnberg (FAU), Martensstr. 5, 91058 Erlangen, Germany

10.1016/j.partic.2021.07.001

Volume 65, June 2022, Pages 32-38

Received 23 March 2021, Revised 14 June 2021, Accepted 1 July 2021, Available online 18 July 2021, Version of Record 20 September 2021.

E-mail: paul.git@fau.de

Highlights

• Carbon particles for application in fluidized bed casting device were studied.

• Carbon glass beads showed Geldart B fluidization behavior at reduced pressures.

• Fluidization velocity decreased with increased temperatures.

• Stable fluidization at absolute pressures reaching from 10 to 100 kPa was observed.

Abstract

Fluidized Carbon Bed Cooling (FCBC) is an innovative investment casting process for directional solidification of superalloy components. It takes advantage of a fluidized bed with a base of small glassy carbon beads for cooling and other low-density particles that form an insulating layer by floating to the bed surface. This so-called “Dynamic Baffle” protects the fluidized bed from the direct heat input from the high-temperature heating zone and provides the basis for an improved bed microstructure. The prerequisites for a stable casting process are stable fluidization conditions where neither collapse of the bed nor particle blow out at excessive bubble formation occur.

This work aimed to investigate the fluidization behavior of spherical carbon bed material in argon and air at temperatures between 20 to 350 °C. Systematic studies at reduced pressures using the FCBC prototype device were performed to understand the stable fluidization conditions at all stages of the investment casting process. The particle shape factor and size distribution characterization and the measurement of the powder’s minimum fluidization velocity and bed voidage show that this material can be fully utilized as a cooling and buoyancy medium during the FCBC process.

Graphical abstract

Keywords

Gas–solid fluidization; Glassy carbon; Reduced pressure; Increased temperature; Fluidized carbon bed

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