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April 13, 2004
Edward BarnardElizabeth HagerKevin McComberJenny Lichter
Outline
Goal Aluminum and Silicone Molds Ceramic Preform and Binders Pressure Vessel and Infiltration Time Calculations Characterization Initial Part Production Challenges and Solutions INITIAL PROTOTYPE ! Future Work Schedule
Goal
The goal of our project is to design a manufacturing process to create a selectively reinforced metal matrix composite.
This project will take the theory developed in Jess Wannasin’s thesis work and scale up to part production.
Our Process
Aluminum Mold
Centrifuge Setup
Silicone Mold
Polytek PLATSIL RTV Silicone Rubber 71-10
Ceramic Preform
SiC 120 Grit(100 µm particles)
Wannasin
Binder
REMET R-25 binder (Prehydrolyzed Ethyl Silicate)
Sintered a SiC preform at 1500°C for 1hr Cut sintered alumina into preform shape
0.00
400.00
800.00
1200.00
10 15 20 25
Binder Concentration (%)
Compressive Strength (psi)
No Sintering
Sintering for 1 hourSilica
http://cyberbuzz.gatech.edu/asm_tms/phase_diagrams/pd/sn_pb.gif
Pressure Vessel Calculations
1.5 2.0
0.125
0.50
But…. there’s a catch:
as the processing temperature increases, σUTS decreases
Swagelok Catalog
New Safety Factors
High Temp = 250 - 300°C
σUTS, High Temp = [0.2 – 0.3] * σUTS, Room Temp
σUTS safety factor
Safety factors sufficient
rinner S. F.
0.75 50.062
515
⎟⎟⎠
⎞⎜⎜⎝
⎛
+−
=22
22
max .. io
ioUTS
rr
rr
FSP
σ Pmax = 730 psi = 50 atm
S. F. : safety factor = 2
Infiltration Time Calculations
Values: = 2* water, L = 4 inches, DP = 100m
P >> Pthreshold and infiltration times << 5 mins
VP = 0.5 VP = 0.7
Threshold pressures 1.5 atm 3.5 atm
Infiltration times <<1 sec <<1 sec
220
3
2.4
)1(
P
P
VS
Vk
••−
=PV
ktL
P
Δ−
=)1(
22
Darcy’s Law: pressure driven flow Blake-Kozeny equation
Hardness Tests
Preparation Cut samples with low-speed saw to obtain smooth
surface blade is material specific part is a combination of materials of very different materials
Polished with 5-micron polishing paper
Results: used Rockwell B and H (low hardness) Pure tin-lead: off-the-scale on the low end hardness MMC: on-scale but low MMC is harder than plain tin-lead
SEM (Scanning Electron Microscopy) Images
SiC particles: 500-600 microns
Fracture behavior
Etchers may be necessary2mm
1mm
100m
Initial Spin tests
Small amount of Tin-Lead Completed cleared out of runner
First Try: Incomplete Infiltration
SiC, 120 grit non-sintered preforms 500 rpm Preform floated Not enough metal or pressure
Challenges and Solutions
Insufficient seal and metal leakage But still safe! Solution: graphite o-ring
Before… After…
Challenges and Solutions, ct’d
Imbalanced centrifuge Prevents centrifuge from reaching high
rpm, reducing volume fraction of ceramic – high Vceramic is the goal
Solution: add weights to either side
However…. still imbalanced
Challenges and Solutions, ct’d
Removing part from mold Graphite o-ring stuck to mold interface Long-term Solution: on future production
runs, spray interface with Boron Nitride Short-term Solution: hit part out with
hammer
INITIAL PROTOTYPE !!!!
Tin Lead, R-25 Binder, 700 RPM = 6 atm Preforms:
sintered SiC, 120 gritsintered alumina
One on left: not full shape because of imbalanced metal distribution (metal left in runner)
Future Work
Make more parts! Try different ceramics Try different binder concentrations Alter shape of part SEM
Volume fraction of particles Fracture characteristics
Hardness tests
Projected Work Schedule
2/5 2/12 2/19 2/26 3/4 3/11 3/18 3/25 4/1 4/8 4/15 4/22 4/29 5/6 5/13
MaterialsMetal choiceCeramics choice
Part productionCADAlum. machined mold
Ceramic preform
Volume fraction Time PermittingSize distribution "
Final testing
CODE:Task Sub-task Gradation Testing