delubrication during stage i of the sintering process · 0,2 0,4 0,6 0,8 1 0 20 40 60 80 100 p e a...

Delubrication during stage Iof the sintering process

Student: Arnaud GateaudAdvisor: Diran Apelian

•Sequence of events during delubrication :Melting of the lubricant vapour formation vapour diffusion through the pores lubricant swept away by the gases in the furnace

•Effects of improper delubrication• Sooting Mechanism: high carbon activity combined

with low convection of gaseous species

• Blistering Mechanism: heating rate too high causingcracks inside the parts, due to Vvaporization >> Vdiffusion

Previous Work (1)

Previous Work (2)*

•Contribution ofProcessing Parameters:

• Heating ratedetermines thekinetics ofdelubrication(65% contribution)

*Deepak Saha’s Master Thesis, WPI, 2001

•Effect of heating rate:•Onset of delubricationdelayed for increasingheating rates.

Previous Work (3)*

•Mathematical model :

(Model validated with 10 P/M samples, 35-36 g each)

•Delubrication fully described by two parameters :• TMAX: intrinsic property of the polymer• b: extrinsic property, which depends on the processing

conditions•Once the system conditions are gauged, the modelpredicts the time required for delubrication.

b

MAXT

T

!!"

#$$%

&+

=

1

1'


Previous Work (4)*

•Hydrocarbons, CO, CO2 and NH3 are released duringdelubrication•Emission profile is bimodal:

• Several emission peaks ~450°C• Release of CO ~725°C


•Ascertain the robustness of the model for high densitycompacts (warm compaction).

•Study the effect of green density and S/V ratio, forvarious compacts compositions, on the kinetics oflubricant removal.

•Study the possible interaction between heating rate andthe presence of Nickel

•Identify the gaseous species emitted duringdelubrication, for various heating rates and compositions.

Objectives of the project

Powders & Lubricants used

•Lubricants used• Acrawax C• Ancormax D

•Composition of the compacts• Reference samples: 99.1% Fe 1000B - 0.3% Gr – 0.6% Lube• Prealloyed Ni samples: 99.1% 4600V – 0.3% Gr – 0.6% Lube• Admixed Ni samples: 97.25% Fe 1000B – 1.85% Inco Ni 123 – 0.3% Gr – 0.6% Lube

0.56---

Mo

1.83------0.150.130.014600V0.050.050.030.100.09<0.01Fe 1000B

NiCuCrMnOCWeight (%)

Compacts used

•Dimensions and mass of the compacts• 32*13*13mm (TRS bars)• 8*25.5mmØ (cylindrical samples)• 29.0g of material for every compact

•Compaction procedure• Regular compaction for Acrawax C• Warm Compaction for Ancormax D (die heated to 145°F – 2 minutes between filling and pressing)

94.39391.890.589.287.986.6Theoretical density (%full)7.357.257.157.056.956.856.75Actual density (g/cm3)maxDmaxD

AWmaxD

AWmaxD

AWAWAW

TGA experiments

•Delubrication atmosphere:• 5% H2 in N2

• Dry atmosphere

•Flow rate of gases: 80 ml/min

•Heating rates:• 5°C/min 10°C/min 15°C/min• Temperature ramp from 100°C to 700°C

•Reactor tube purged for 30min, before each run.

TGA experiments

•All measurements corrected for Buoyancy Forces•Compacts replaced by a 34mm*11mmØ glass rod•Parameters involved:

• Samples have to be replaced by a similar volume• Similar geometry (if possible)• Similar mass (if possible)

Buoyancy forces - 15°C/min

0

1

2

3

4

5

0 100 200 300 400 500 600 700

Temperature (°C)

Mass (

mg

)

Data used forbackground

substraction

Model applied to Ancormax D

•Validity of the model has been extended to Ancormax D.

Blue line: modelRed line: experiment

Delubrication of aFE-C-maxD compact at 10°C/min

Effect of Nickel on Tmax

AW-lubricatedcompacts(6.95g/cm3)

maxD-lubricatedcompacts

(7.25g/cm3)

Effect on Nickel on Tmax - Acrawax C

Heating rate (°C/min)

4 6 8 10 12 14 16

Tm

ax (°C)

380

400

420

440

460

480

Fe 1000B - Gr.

Fe 1000B - Inco Ni 123 - Gr.

4600V - Gr.

Effect of Nickel on Tmax - Ancormax D


4 6 8 10 12 14 16

Tm

ax (°C)

380

400

420

440

460

480

Fe 1000B - Gr.

Fe 1000B - Inco Ni 123 - Gr.

4600V - Gr.

Effect of Nickel on ‘b’

AW-lubricatedcompacts(6.95g/cm3)

maxD-lubricatedcompacts

(7.25g/cm3)

Effect of Nickel on 'b' - Acrawax C


4 6 8 10 12 14 16

'b'

19

20

21

22

23

24

25

26

27

Fe 1000B - Gr.

Fe 1000B - Inco Ni 123 - Gr.

4600V - Gr.

Effect of Nickel on 'b' - Ancormax D


4 6 8 10 12 14 16

'b'

24

26

28

30

32

34

36

38

40

Fe 1000B - Gr.

Fe 1000B - Inco Ni 123 - Gr.

4600V - Gr.

Effect of Nickel – Statistical Analysis

% contribution of Ni / H.R. onAcrawax C removal kinetics

% contribution of Ni / H.R. onAncormax D removal kinetics

Statistical effect on 'b' - Ancormax D

Nickel

5%

Error

5%

Heat. rate

90%

Statistical effect on 'b' - Acrawax C

Nickel

9%

Error

3%

Heat. rate

90%88%

Effect of green density on Tmax & ‘b’

Evolution of Tmax withincreasing density

Evolution of ‘b’ withincreasing density

Effect of green density on Tmax (10°C/min)

% full density

86 88 90 92 94 96

Tmax (°C

)

400

410

420

430

440

450

Fe 1000B - Gr. (AW)

Fe 1000B - Inco Ni 123 - Gr. (AW)

4600V - Gr. (AW)

Fe 1000B - Gr. (maxD)

Fe 1000B - Inco Ni 123 - Gr. (maxD)

4600V - Gr. (maxD)

Effect of Green Density on 'b' (10°C/min)

% full density

86 88 90 92 94 96

'b'

10

15

20

25

30

35

40

Fe 1000B - Gr. (AW)

Fe 1000B - Inco Ni 123 - Gr. (AW)

4600V - Gr. (AW)

Fe 1000B - Gr. (maxD)

Fe 1000B - Inco Ni 123 - Gr. (maxD)

4600V - Gr. (maxD)

Effect of compact geometry (S/V ratio)

Actual S/V (mm-1)0.407 0.383

Open porosity Correction factor

Ω=3.84 characterizes the ratio[open porosity]TOP/[open porosity]SIDE

Fe 1

000B

- SI

DE

(6.9

5g/c

m3 )

Fe 1

000B

- TO

P(6

.95g

/cm

3 )

Side surfacecorrection factor:

ψ=0.51

Top surfacecorrection factor:

Ω ψ =1.97

Effect of compact geometry (S/V ratio)

Actual S/V (mm-1)0.407 0.383

Open porosity-corrected S/V (mm-1)0.572 0.439

FTIR GC/Mass Spec. experiments

•Same processing conditions:• Atmosphere• Flow rate of gases• Heating rates• Compacts

•Data acquisition• Online FTIR

measurements• Delubrication products

condensed from volatile ina LN2 trap analyzedwith GC/MS.

Experimental setup

FTIR calibration

Calibration CH4

0

0,05

0,1

0,15

0,2

0,25

0 20 40 60 80 100

Pe

ak

In

ten

sit

y

Calibration CO2

0

0,01

0,02

0,03

0,04

0,05

0 20 40 60 80 100

Pe

ak

In

ten

sit

y

Calibration C2H4

0

0,2

0,4

0,6

0,8

1

0 20 40 60 80 100

Pe

ak

In

ten

sit

y

Calibration CO

0

0,05

0,1

0,15

0,2

0,25

0 20 40 60 80 100

Pe

ak

In

ten

sit

y

•Calibration performed in order to correlate themeasured peak intensities.

FTIR Measurements

•Data collected with software OMNIC•Sampling time for data collection is 1 min

• IR glass cell is heated to 200°C during runs• In 1 min, half of the cell atmosphere is renewed• IR cell exhaust is connected to a LN2 trap.

Typical emission profile forFe-C-AW compact at

delubrication temperature

Hydrocarbons

CO

CO2

FTIR data – Emission profiles @ 5°C/min

Acrawax C - 5°C - Emission profiles

Temperature (°C)

300 400 500 600 700 800

Inte

ns

ity

-0,1

0,0

0,1

0,2

0,3

0,4

0,5

0,6


Acrawax C - 5°C/min - Emission profiles

Temperature (°C)

300 400 500 600 700 800

Inte

ns

ity

-0,1

0,0

0,1

0,2

0,3

0,4

0,5

0,6



Temperature (°C)

300 400 500 600 700 800

Inte

ns

ity

-0,1

0,0

0,1

0,2

0,3

0,4

0,5

0,6

FTIR data – Emission profiles (Fe 1000B)

Acrawax C - Fe 1000B - Emission profiles

Temperature (°C)

300 400 500 600 700 800

Inte

ns

ity

-0,1

0,0

0,1

0,2

0,3

0,4

0,5

0,6

FTIR data – Emission profiles (Ni admixed)

Acrawax - Fe Ni - Emission profiles

Temperature (°C)

300 400 500 600 700 800

Inte

ns

ity

-0,1

0,0

0,1

0,2

0,3

0,4

0,5

0,6

FTIR data – Emission profiles (Ni admixed)

Acrawax C - Fe Ni - Emission profiles

Temperature (°C)

300 400 500 600 700 800

Inte

ns

ity

-0,1

0,0

0,1

0,2

0,3

0,4

0,5

0,6

FTIR data – Emission profiles (Ni preall.)

Acrawax C - 4600V - Emission profiles

Temperature (°C)

300 400 500 600 700 800

Inte

nsity

-0,1

0,0

0,1

0,2

0,3

0,4

0,5

0,6



Temperature (°C)

300 400 500 600 700 800

Inte

ns

ity

-0,1

0,0

0,1

0,2

0,3

0,4

0,5

0,6



Temperature (°C)

300 400 500 600 700 800

Inte

nsity

-0,1

0,0

0,1

0,2

0,3

0,4

0,5

0,6

Predominance of long chain hydrocarbons

Methane [6170 ppm]FTIR characteristic pattern

26.9% of CH4 total area

Pyrolysis of Acrawax C4600V - 10°C/min (@ 501°C) Long-chain hydrocarbons (93.6%)

6.4% signal

GC/MS preliminary results

Alkane/alkene double peaks.

# o

f co

unts

Retention time (min)

Conclusions (1/2)

•Compact density has little effect on the kinetics oflubricant removal, especially for EBS.

•The empirical model was extended and verified forwarm-compacted P/M parts.

•Nickel affects the kinetics of delubrication, but thereis no interaction between presence of Nickel and heatingrate.

•A correction factor Ω can be defined to take intoaccount more accurately the effect of S/V ratios.

Conclusions (2/2)

•Emission profile patterns of volatile gaseous products(CO, CO2, hydrocarbons) have been identified.

•Numerous hydrocarbons resulting from thedecomposition of EBS have been identified.

•For green parts weights < ~1.0 oz. (30g), lubricantdecomposition/evaporation was proved to be thekinetically limiting factor.

delubrication during stage i of the sintering process · 0,2 0,4 0,6 0,8 1 0 20 40 60 80 100 p e a...

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