1. Motivation Computational simulation is more efficient on composition and process parameters optimization.Cemented carbide is widely used as cutting, grinding and drilling tools.Ø

Ø

3. Thermodynamic and diffusion databases

Data collection

Key experiments

thermodynamic and kinetic description

Microstructure simulation

Process optimization

Feedback

Phase equilibriumThermodynamic factorTransformation driveDiffusion coefficients

Development through a large degree of mechanical testing is expensive and time consuming.

Ø

Numerous process parameters strongly influence the microstructure andperformance.

2. ICME in cemented carbides

Computational simulation is a powerful tool for process optimization.Ø

Interface modelInterface energyElastic energy

Alloy compositionGas pressure & constituentSintering temperature & timemoreover...

CSUTDCC1:

CSUDDCC1:

Central South University Thermodynamic Database for Cemented Carbides-version-1

Central South University Diffusion Database for Cemented Carbides-version-1

1050°C

Mole

fra

ctio

n C

Mole fraction Cr

aCr2Nb

fcc

hcp

Cr3C2

Cr7C3

Cr23C7

Single phase

Two phases

Three phases

fcc: (Cr,Nb)C

hcp: (Cr,Nb)2C

(Co)

σ

Co2Ti+σ σ+(Co)

Co2Ti+B2

χ+σ+Co2Ti

χ+Co2TiCo2Ti

χ+σ+(Co)

1050˚C

(αCo)

χ

σ

B2

L12

Co2Ti+(Co) χ+(Co) χ+σχ+Co2Ti

Co2Ti(c)

Co2Ti(h)0

10

20

30

40

50

60

10 20 30 40 50 600Mass percent, Ti

Mas

s

, Cr

perc

ent

4.1 Design of composition and temperature

-8.6

-8.4

-8.2

-8.0

-7.8

-7.6

-7.4

-7.2

-7.0

3.0 3.5 4.0 4.5 5.0 5.5 6.0

10000/T(1/K)

Lo

g1

0D

Co

2(m

/s)

Co

Theoretical data

Iida et al. 2006 Yang et al. 2009

Han et al. 2004 Pasianot's EAM Stoop's EAM

Yokoyama et al. 1999 Yokoyama et al. 2001

1765K

DICTRA results

This work

Frykholm et al. 2001

Represent resultsØ

4. Application

Te

mp

era

ture

, ºC

WC-11Co-0.1Cr

Carbon poor

Carbon rich

Sintering region

WC-11Co-0.6Cr

Carbon poor

Carbon rich

Sintering region

Mass fraction C

WC-11Co-1.1Cr

Carbon poor

Carbon rich

Sintering region

Mass fraction C Mass fraction C

M7C3

A small amount addition of Cr

4.2 Control of the stability of cubic phase

M(C, N)x + W(C,N) + graphite

TiC

TiN

WC

WN

Mole Fraction WC

Mo

le F

racti

on

TiN

M(C, N)x +graphite

M(C, N)x #1 M(C, N)x #2 ++ W(C,N) + graphite

M(C, N)x + graphite

M(C, N)x + W(C,N) + graphite

T=1427°C

1973 K

1873 K

1773 K1673 K1573 K

y in NbC0.487Ny

log

10P

N2 (

atm

)

0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2

0 100 200 300 400 500

Mo

le p

erc

en

t

Distance, μm

Matano plane

Ta NbCo-1.86 at.%Ta

Co-1.27 at.%Nb

Grain growth inhibitor

Improve corrosion resistance

Reduce melting temperature

Bring unwanted M7C3 phasewith too much addition

Mass fraction C

Te

mp

era

ture

,°C

WC-8Co-14TiC-4ZrC

fcc_Co + + + WC

(Ti, Zr)C#1(Ti, Zr)C#2

fcc_Co + (Ti, Zr)C#1 + (Ti, Zr)C#2 + WC + M6C

liquid + + + WC

(Ti, Zr)C#1 (Ti, Zr)C#2

liquid + + WC

(Ti, Zr)C

#1

#2

I. Borgh et al., Acta Materialia, 66(2014) 209-218.

Control the decomposition of carbonitrides

Control the formation of a second cubic phase used as a strengthening constituent

4.3 Gradient cemented carbide

Vacuum

10 mbar

20 mbar

30 mbar

40 mbar

4

6

8

10

12

14

16

18

20

Th

ickn

ess o

f g

rad

ien

t zo

ne

, μm

0 5 10 15 20 25 30 35 40

PN2, mbar

16.4 μm

10.1 μm

7.16 μm

5.61 μm

4.80 μm

Experimental data

Calculated data

0

20

400 10 20 30 40 50 60 70 80

4

6

8

10

12

14

16

18

5

6

7

8

9

10

11

12

13

14

15

Distance, μm

Ma

ss

pe

rce

nt C

o

PN

2, mbar

Co peak

Co surface

0

20

400 10 20 30 40 50 60 70 80

0

1

2

3

4

5

6

7

8

9

10

1

2

3

4

5

6

7

Distance, μm

Ma

ss

pe

rce

nt T

i

PN

2, mbar

Ti peak

Ti Co

6.35C-7.5Co-5Ti-0.1N-W cemented carbides sintered under various N2 pressure at 1450 ℃ for 1 h

4.4 Cellular cemented carbide

0.000 0.005 0.010 0.015 0.020 0.025 0.030

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

Ma

ss f

racti

on

Co

Distance, m

Experimen t [14]

Simul at ion [Th is wor k]

Ini tial Prof ile

WC-5Co WC-30Co

T=1400°Ctime=3 60s

100µm

High Co contentCoarse WC particle

low Co content Fine WC Particle

1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

0.22

Ma

ss

fra

cti

on

Co

Grain size, μm

T=1400°Ctime=3600s

diffusion couple A

Initial Co content

Simulation [This work]

Experiment [This work]

diffusion couple B

Layer 1

Layer 2

Layer 1

10µm

WC particle (3.0 µm) Co content (10.2 wt.%)

10µm

interface

WC particle (2.9 µm) Co content (19.5 wt.%)

interface

WC particle (1.8 µm) Co content (11.8 wt.%)

WC particle (1.8 µm) Co content (21 wt.%)

diffusion couple A diffusion couple B

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

V

olu

me

fra

cti

on

Liq

uid

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8Mass fraction Co

WC+Liquid

Liquid

Fcc_Co

Fcc_Co+LiquidT=1400°C

2u=-0.0011+0.431×m+0.096×m 3 4+0.165×m +0.033×m

( a )

800

900

1000

1100

1200

1300

1400

1500

1600

1700

1800

Te

mp

era

ture

, °C

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0WC CoMass fraction Co

WC+LiquidLiquid

Fcc_Co+Liquid

Fcc_Co

Fcc_Co+WC

WC-70CoWC-30Co WC-70CoWC-30Co

WC-20CoWC-5Co

0.9 1.0

( b )

Calculated relationship between mass fraction and volume fraction

low Co content high Co content

Concentration profile

Equilibrium Co content of the diffusion couples

SEM micrograph 2D&3D elemental distributions

WCNi3Al

10µm

C

(a)(a)

WC

WC

WC

Ni Al3

WC

Ni Al3

(100)WC

(010)WC

(100)WC

(010)WC

(b)

(100)WC

(110)WC

(010)WC

(110)WC

(220)

(110)

(d)

(022)Ni Al3

(311)Ni Al3

Ni Al3

Ni Al3

(c)

Experimental results

T=1450 °C

T=900 °C

0.04 0.045 0.05 0.055

So

lub

ilit

y o

f W

in

bin

der

ph

ase,

wt%

C content,wt%

0

0.1

0.2

0.3

0.4

0.5

0.6

1370

1380

1390

1400

1410

1420

1430

1440

1450

Tem

per

atu

re, °

C

0.6 0.7 0.8 0.9 1.0

Mole fraction of solid phase

1

1

1

12

345 6578

1: Liq+WC2: Fcc_L12 Liq WC3: Bcc_A1 Liq4: Bcc_A1 Fcc_L12 Liq5: Bcc_A1 Fcc_L12 Liq WC6: Bcc_A1 Fcc_L12 WC7: Bcc_A1 Fcc_L12 Hcp_A3 Liq WC8: Bcc_A1 Fcc_L12 Liq Hcp_A3

1

Scheil

Equilibrium

TEM analysis of WC/Ni3Al interface

SEM micrograph

5. Conclusion

0

0.05

0.10

0.15

0.20

0.25

0.30

0 0.05 0.10 0.15 0.20 0.25 0.30

Fcc_L

12+L

IQ+W

C

Fcc_L

12+G

RA

+LIQ

Hcp_A3+Liq+WC

Hcp_A3+Liq+Bcc_B2

W

Mol

e fr

acti

on o

f C

Mole fraction of W LiquidNi-25.at% Al

T=1500 °C

Liq+WC

alloy composition

Self-consistent thermodynamic and diffusion databases for cemented carbide system C-W-Co-Fe-Ni-Al-Cr-V-Mo-Ta-Ti-Nb-Zr-N have been established

ØSome examples of using thermodynamic and kinetic simulations to design and/or optimize the process parameters have been illustrated

Ø

The presently established databases have been successfully applied in the development of gradient and cellular cemented carbides, and cemented carbides with composite Ni3Al as binder phase.

Ø

Acknowledgements

National Natural Science Foundation of China (Grant No. 51371199)

Dctoral Scientific Fund Project of the State Ecation Committee of China(Grant No.20120162110051)

Zhuzhou Cemented Carbide Cutting Tools Co., LTD of China

Diffusivities in liquid and fcc Co-based alloys

C-Cr-Nb Co-Cr-Ti

Thermodynamic and diffusion databases of cemented carbides: their applications to development of new cemented carbides

1 1,* 1Yingbiao Peng , Yong Du , Peng Zhou Weimin Chen , 1 2 2 2Shuhong Liu , Shequan Wang , Guanghua Wen , Wen Xie

1 1 1 1Weibin Zhang , , Kaiming Cheng , Lijun Zhang ,

1 State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083, China2 Zhuzhou cemented carbide cutting tools limited company, Zhuzhou, 412007, China

Sino-German Cooperation Group "Microstru cture in Al alloys"

中德“铝合金微结构”联合实验室

硬质合金微结构研究小组

Microstructure in Cemented Carbide Cooperation Group

CENTRAL SOUTH UNIVERSITY

Experiment phase equilibria/constituent diffusion in binder phase FP calculation

thermodynamic properties interface information

A thermodynamic database was established by SANDVIK,

however, not commercially available!Ø

Introducing gradient surface zone (enriched in binder phase) to prevent crack propagationØ

Aim: i) Establish thermodynamic and diffusion databases for cemented carbides ii) Develop cemented carbides based on computational simulations

PerformanceMicrostructure

Advanced material

Databases

DICTRAThermo-Calc

Quantitatively control the gradient zone formationØUnderstand the liquid phase migration during sintering processSuccess in the design of the initial composition for raw materialsØ

Initially designed microstructure could survive the liquid phase sintering processØ

Ø

Improving the high-temperature and corrosion resistance properties by using composite binderØ

Guide the development of new cemented carbidesØ

W

WC

Hcp_A3

1300 °C

Mole fraction W

Two-phase region

Three-phase region

Fcc_A10 0.2 0.4 0.6 0.8 1.0

Mol

e fr

acti

on C

M12CM6C

M4C

C-Ni-W

-9.0

-8.8

-8.6

-8.4

-8.2

-8.0

-7.8

-7.6

-7.4

4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5

Meyer et al. 2009

Lo

g1

0D

Ti

2(m

/s)

Ti

1998K

DICTRA results

This work

Frykholm et al. 2001

Experimental data

Theoretical data

Iida et al. 2006

ModZoMZoM

Xia et al. 2011

10000/T(1/K)

liquid Co liquid Ti

20 binary systems35 ternary systems6 quaternary systems

Experimental & assessed (fcc_A1)

Predicted (liquid)

14 elements

Experimental & assessed

18 ternary systems

Reassessed

10 binary systems34 ternary systems12 quaternary systems

C-W-Co-Fe-Ni-Al-Cr-V-Mo-Ta-Ti-Nb-Zr-N

4.5 Design of new binder phase