Posted by Gordon England (188.8.131.52) on 14:05:56 14/05/06
In Reply to: metallographic preparation of al2o3 coating posted by jaro polak
First - Try impregnating your sample with epoxy resin ideally
using vacuum impregnation. This helps to hold things together and
helps with identification of true porosity (filled with
resin)and pull-out (not filled with resin).
Second - use fresh sharp abrasives, do not overwork them. The idea is to cut and not to burnish.
Third - after pre-grinding use hard napless clothes, nylon or ideally silk with no soft backing materials with diamond abrasives and then alumina or preferably colloidal silica. It is important to keep looking at your sample under the microscope at regular intervals or between stages to evaluate your progress. If you identify excessive pull-out at any stage you will need to start again from scratch and modify your procedure. Final stages may need to be prolonged
using colloidal silica or alumina.
Forth - finally only use a soft cloth for a short time with alumina or colloidal silica if you want to develop a relief effect to identify unmelts and phases.
Experiment, learn from your mistakes, this is what makes good metallographers.
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