Evolution of liquid-bond strength in powder injection moulding compact during thermal debinding: Numerical simulation

Shengjie Ying, Y. C. Lam, J. C. Chai

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Debinding is a critical processing step in the powder injection moulding (PIM) process. Thermal debinding is a common methodology for the final removal of residual polymer from a PIM compact prior to sintering. During debinding, the strength of the compact decreases rapidly due to heating and polymer removal. Liquid-bond strength plays a key role in the strength of the compact. Simulation of the liquid-bond strength in the compact during thermal debinding, based on the model which has previously been validated experimentally, is proposed. The pyrolysis of polymer, heat transfer, and multi-phase fluid flow, i.e. liquid flow, gas flow, vapour diffusion, and convection, as well as liquid-bonding forces arising from capillary suction pressure and interfacial surface tension, and their interactions, are considered simultaneously. The simulated results revealed that the liquid-bond strength in the compact decreases rapidly as furnace temperature increases, because the surface tension and capillary pressure decrease rapidly with an increase in temperature. The effect of softening caused by elevated temperature is more significant than the effect of weakening caused by polymer removal. Thus, thermal debinding at lower temperatures will contribute towards prevention of defect formation.

LanguageEnglish
Pages311-323
Number of pages13
JournalModelling and Simulation in Materials Science and Engineering
Volume12
Issue number2
Early online date16 Feb 2004
DOIs
Publication statusPublished - Mar 2004
Externally publishedYes

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Injection Molding
injection molding
Bond strength (materials)
Powder
Injection molding
Powders
Liquid
Polymers
Numerical Simulation
Computer simulation
Liquids
liquids
Capillarity
polymers
Surface Tension
simulation
Decrease
Surface tension
interfacial tension
Interfacial Tension

Cite this

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AB - Debinding is a critical processing step in the powder injection moulding (PIM) process. Thermal debinding is a common methodology for the final removal of residual polymer from a PIM compact prior to sintering. During debinding, the strength of the compact decreases rapidly due to heating and polymer removal. Liquid-bond strength plays a key role in the strength of the compact. Simulation of the liquid-bond strength in the compact during thermal debinding, based on the model which has previously been validated experimentally, is proposed. The pyrolysis of polymer, heat transfer, and multi-phase fluid flow, i.e. liquid flow, gas flow, vapour diffusion, and convection, as well as liquid-bonding forces arising from capillary suction pressure and interfacial surface tension, and their interactions, are considered simultaneously. The simulated results revealed that the liquid-bond strength in the compact decreases rapidly as furnace temperature increases, because the surface tension and capillary pressure decrease rapidly with an increase in temperature. The effect of softening caused by elevated temperature is more significant than the effect of weakening caused by polymer removal. Thus, thermal debinding at lower temperatures will contribute towards prevention of defect formation.

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