11 - BCERS water debinding-4-diapo Debinding methods Supercritical or catalytic debinding Solvent...

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Transcript of 11 - BCERS water debinding-4-diapo Debinding methods Supercritical or catalytic debinding Solvent...

  • - www.bcrc.be info@bcrc.be Tél: 065/40 34 34

    Predictive model applicable to water debinding of complex shape parts injection molded using

    commercial feedstock

    Vedi Dupont C. Delmotte, J.P. Erauw, F. Cambier (1)

    T. Boulanger, C. Emmerechts, B. Guerra, E. Beeckman (2)

    (1) BCRC, Belgian Ceramic Research Centre 4, Avenue Gouverneur Cornez, 7000 Mons, Belgium.

    (2)SIRRIS 12, rue Bois Saint Jean, 4102 Seraing, Belgium

    BCERS Febuary 7 th 2011, Mons

    - www.bcrc.be info@bcrc.be Tél: 065/40 34 34

    Contents

    � Introduction

    � Results and discussion

    � Conclusion & perspectives

    • CIM (Ceramic Injection Molding) • Definition of feedstocks • Goal & approach of the model

    • Influence of temperature, and geometry during a water debinding step

    • Evolution of the microstructure • Influence of water debinding conditions on sintering behavior

    BCERS Febuary 7 th 2011, Mons 2

  • - www.bcrc.be info@bcrc.be Tél: 065/40 34 34

    Ceramic Injection Molding

    Industrial sector's concern : shaping of complex advanced ceramics parts - Selection of competitive forming method(s) - Low cost of processing and high end-product performance

    CIM (CERAMIC INJECTION MOLDING) is more and more present on world markets.

    Advantages : - Suited for the production of complex ceramic parts with precision , speed , and repeatability . - Less assembling and /or manipulation steps.

    � 4 successive steps 1. Plasticizing 2. Injection 3. Strengthening 4. Ejection

    BCERS Febuary 7 th 2011, Mons 3

    - www.bcrc.be info@bcrc.be Tél: 065/40 34 34

    In the past: � formulation by ceramic producer

    • Proportion powder-additives • Nature of binder & plasticizer • Nature of powder • Nature of adjuvants � Composition and behavior of feedstock clearly known

    Today : � existence of commercial feedstocks • Ready-to-use • Composition unknown • No detailed technical data � Composition and behavior of commercial feedstocks "unknown"

    What is a feedstock ?

    BindersBinders

    Ceramic Powder

    Homogenization

    Granulation

    AdditivesAdditives

    Feedstocks

    BCERS Febuary 7 th 2011, Mons 4

  • - www.bcrc.be info@bcrc.be Tél: 065/40 34 34

    Disadvantage of CIM

    Existence of a critical step :

    Removal of the large amount of additives

    Debinding methods

    Debinding methods

    Supercritical or catalytic debinding

    Supercritical or catalytic debinding

    Solvent debinding

    Solvent debinding

    Water debinding

    Water debinding

    - low cost - environmental friendly

    Classical thermal

    debinding

    Classical thermal

    debinding

    Cr uc

    ial st

    ep

    � Several debinding methods of CIM parts

    BCERS Febuary 7 th 2011, Mons 5

    - www.bcrc.be info@bcrc.be Tél: 065/40 34 34

    Recommendations of the supplier :

    � Debinding step - 24h in water(25°C) - thermal (HR : 20 to 2 °C / h)

    � Sintering - 1600°C (HR : 130 °C / h)

    Recommendations of the supplier :

    � Debinding step - 24h in water(25°C) - thermal (HR : 20 to 2 °C / h)

    � Sintering - 1600°C (HR : 130 °C / h)

    80*20*5 mm3

    Necessity to predict the time needed to remove a maximum fraction of the

    soluble binder

    As a function of geometry, temperature and immersion duration in water

    Damaged part Swelling & Cracking

    80*20*2 mm3

    Sound part

    Disadvantage of CIM

    BCERS Febuary 7 th 2011, Mons 6

  • - www.bcrc.be info@bcrc.be Tél: 065/40 34 34

    Previous works

    Lin & German : � For a infinite geometry, fraction of soluble binder remaining , Ln (1/F) = f (t)

    with t immersion time

    Shivashankar & German : � Extension of previous model for a finite geometry � Introduction of a new parameter : 1/Ψ (= S / V ) length scale

    1

    2

    ) 1

    ln( K tD

    F += 2ψ

    π

    BCERS Febuary 7 th 2011, Mons 7

    - www.bcrc.be info@bcrc.be Tél: 065/40 34 34

    Goal & approach

    Elaborate a predictive model of the water debinding of complex molded parts, to ease thermal post treatmen ts

    Simple shapes Parameters :

    - Geometry

    - Immersion time

    - TemperatureElaboration of predictive model

    Weight losses measured

    Model validation Post-treatmentsReal complex shapes

    Weight losses calculated

    Weight losses measured

    BCERS Febuary 7 th 2011, Mons 8

  • - www.bcrc.be info@bcrc.be Tél: 065/40 34 34

    Experimental procedure

    � Preparation of samples - Injected at 160°C (Arburg 350-90 A270D), Alumina feedstock (Al2O3). - Debinded in stirred water at 25°, 40°et 55°C for varying immersion times. - Dried at 50°C during 48h .

    Bars Cylinders

    e (mm) 1.6 2.6 3.6 1 3 6

    1/Ψ = S/V 1.477 0.997 0.748 2.250 0.917 0.583

    60x10xe ∅16xe

    Simple shapes Real complex shapes

    Heat sink Nozzle

    1/Ψ = 0.731 1/Ψ = 0.822

    BCERS Febuary 7 th 2011, Mons 9

    Wide range of the length scale

    - www.bcrc.be info@bcrc.be Tél: 065/40 34 34

    Results and discussion

    BCERS Febuary 7 th 2011, Mons 10

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    Influence of the temperature

    Fraction of soluble binder remaining in the green (F) is expressed by :

    *

    •S.T.Lin, R.M.German, PMI vol 21 n° 5, 1989, pp 19-24.

    With Ψ = V / S

    1

    2

    ) 1

    ln( K tD

    F += 2ψ

    π

    � Estimation of maximum weight loss in water :

    W max (feedstock) ~ 6 %

    BCERS Febuary 7 th 2011, Mons 10

    - www.bcrc.be info@bcrc.be Tél: 065/40 34 34

    0

    0,2

    0,4

    0,6

    0,8

    1

    1,2

    0 5 10 15 20 25 30

    Ln (1

    /F )

    t/Ψ2 (h.mm -2)

    Plot of Ln(1/F) against t/Ψ2 at different temperatures : Al2O3 (1/Ψ = 0.748)

    25 °C

    40 °C

    55 °C

    BCERS Febuary 7 th 2011, Mons 11

    Influence of the temperature

    25°C 40°C 55°C

    0

    0,2

    0,4

    0,6

    0,8

    1

    1,2

    0 5 10 15 20 25 30

    Ln (1

    /F )

    t/Ψ2 (h.mm -2)

    Plot of Ln(1/F) against t/Ψ2 at different temperatures : Al2O3 (1/Ψ = 0.748)

    Diffusion controlled stage

    Dissolution controlled stage

  • - www.bcrc.be info@bcrc.be Tél: 065/40 34 34

    0

    0,2

    0,4

    0,6

    0,8

    1

    1,2

    0 5 10 15 20 25 30

    Ln (1

    /F )

    t/Ψ2 (h.mm -2)

    Plot of Ln(1/F) against t/Ψ2 at different temperatures : Al2O3 (1/Ψ = 0.748)

    25 °C

    40 °C

    55 °C

    BCERS Febuary 7 th 2011, Mons 11

    Influence of the temperature

    25°C 40°C 55°C

    0

    0,2

    0,4

    0,6

    0,8

    1

    1,2

    0 5 10 15 20 25 30

    Ln (1

    /F )

    t/Ψ2 (h.mm -2)

    Plot of Ln(1/F) against t/Ψ2 at different temperatures : Al2O3 (1/Ψ = 0.748)

    Diffusion controlled stage

    Dissolution controlled stage

    0

    0,2

    0,4

    0,6

    0,8

    1

    1,2

    0 5 10 15 20 25 30

    Ln (1

    /F )

    t/Ψ2 (h.mm -2)

    Plot of Ln(1/F) against t/Ψ2 at different temperatures : Al2O3 (1/Ψ = 0.748)

    25°C 40°C 55°C

    Diffusion controlled stage

    Dissolution controlled stage

    � 2 stages observed :

    1. Dissolution controlled stage

    �Binder just near the sample surface can dissolve quickly.

    R limiting : Dissolution of binder at binder water interface.

    2. Diffusion controlled stage

    �Binder water interface moves inwards in the sample. Creation of a porous network within the green body.

    R limiting : Diffusion of the solutes in the porous paths .

    - www.bcrc.be info@bcrc.be Tél: 065/40 34 34

    • If 1 / Ψ (S / V) is high

    Thin parts

    Large contact surface between soluble binder and

    solvent (water)

    Kinetic of binder extraction is faster

    BCERS Febuary 7 th 2011, Mons 12

    Influence of the geometry

  • - www.bcrc.be info@bcrc.be Tél: 065/40 34 34

    y = 0,0219x + 0,2338

    0

    0,2

    0,4

    0,6

    0,8

    1

    1,2

    1,4

    0 10 20 30 40 50

    Ln (1

    /F )

    t/Ψ2 (h.mm -2)

    Plot of Ln(1/F) against t/ Ψ2 for different values of 1/ Ψ : Al 2O3 at 40 C : Diffusion controlled stage

    � Diffusion controlled stage (T = 40°C)

    � Inter-diffusion coefficient

    Using the Shivashankar-German model,

    1/Ψ range 0.583 - 0.917

    Inter-diffusion coef D (cm2.s-1 )

    6.16.10-5

    BCERS Febuary 7 th 2011, Mons 13

    Influence of the geometry

    - www.bcrc.be info@bcrc.be Tél: 065/40 34 34

    )exp(0 TR

    E DD act−=

    � Inter-diffusion coefficient D : follows an Arrhenius law

    Diffusion controlled stage

    Temperatures D (cm2.s-1)

    25°C 4,92.10-5

    40°C 6,16.10-5

    55°C 6,61.10-5

    Stage D0 (cm 2.s-1) Eact (KJ.mol

    -1)

    Diffusion 1.65.10-3 8.38

    2 K t)( f ) 1

    ( + ,Ψ ,Τ = F

    Ln

    )673,0.0028,