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'
*Deepak Saha’s Master Thesis, WPI, 2001
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
*Deepak Saha’s Master Thesis, WPI, 2001
•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
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 ‘b’
AW-lubricatedcompacts(6.95g/cm3)
maxD-lubricatedcompacts
(7.25g/cm3)
Effect of Nickel on 'b' - Acrawax C
Heating rate (°C/min)
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
Heating rate (°C/min)
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
FTIR data – Emission profiles @ 5°C/min
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
FTIR data – Emission profiles @ 10°C/min
Acrawax C - 10°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
FTIR data – Emission profiles @ 10°C/min
Acrawax C - 10°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
FTIR data – Emission profiles @ 15°C/min
Acrawax C - 15°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
FTIR data – Emission profiles @ 15°C/min
Acrawax C - 15°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
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 (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 (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 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
FTIR data – Emission profiles (Ni preall.)
Acrawax C - 4600V - 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
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.
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