AM Sample Preparation for SRAS and EBSD
Mount the samples in a 30mm diameter conductive resin (Black).
Grind down to at least P1200 paper.
The final run of grinding for each paper should be done in one direction.
The first run of the next paper should be done 90° to the previous direction.
This way you know when to step down a paper when all the scratches on the surface are in the same direction.
Cleanliness and watermarks are not a big deal at this point.
You then use a P4000 paper or 6um diamond paste lapping wheel.
P4000 is actually a higher finish than 6um diamond.
Use gloves and clean samples between each stage, make an effort to minimise cross-contamination at these two stages.
Then use the 1um diamond paste lapping wheel.
This is good enough for SRAS and once perfected can be done in about half an hour (for a nickel super alloy sample).
Ideally, use new clean gloves at this stage and minimise cross-contamination.
Place the samples in the automated polishing machine with a final polishing cloth (black neoprene cloth suck to a disk).
Run it for about 10 minutes using just water, the fore should be set to about 50% at max speed.
Next set the machine to the minimum speed and the force to about 75%.
Use about 25ml of 0.1um SiO2 suspension fluid, water down using deionized water at a ratio of 1:1. Pour onto the cloth at the rate of about one drop per second or a tad less if possible. This 50ml mix should last about 10 minutes. Good practice to stop the machine at 5 minutes and check the force is still 75%. Anything more than about 10 minutes is a waste of time.
Do the same as above using 0.06um SiO2 suspension fluid. Again this mix should last you about 10 minutes.
Finally whilst the machine is running pour deionized water to clear off the SiO2 suspension fluid (until the white stuff gets washed off the pad around the sample, and most of the pad is black again).
When handling the sample be as clean as possible. Place the samples in a beaker with deionized water and place the beaker in the ultrasonic bath for about 10-15 minutes.
At this stage, the samples might look clean but there still might be a lot of SiO2 suspension fluid across the sample. Follow the “How to clean a sample prior to lithography” on the optics wiki to fully remove this and have them beautifully clean for EBSD.