april 13, 2004 edward barnard elizabeth hager kevin mccomber jenny lichter

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