April 13, 2004 Edward Barnard Elizabeth Hager Kevin McComber Jenny 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 Silica

Pressure Vessel Calculations But…. there’s a catch: as the processing temperature increases, σ UTS decreases

Swagelok Catalog New Safety Factors High Temp = °C σ UTS, High Temp = [0.2 – 0.3] * σ UTS, Room Temp σ UTS  safety factor Safety factors sufficient r inner S. F P max = 730 psi = 50 atm S. F. : safety factor = 2

Infiltration Time Calculations Values:  = 2*  water, L = 4 inches, D P = 100  m P >> P threshold and infiltration times << 5 mins V P = 0.5V P = 0.7 Threshold pressures1.5 atm3.5 atm Infiltration times<<1 sec Darcy’s Law: pressure driven flowBlake-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: microns Fracture behavior Etchers may be necessary 2mm 1mm 100  m

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 V ceramic 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 grit sintered 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