Question

1. Why is sectioning and mounting necessary for sample preparation?

2. Why is polishing is necessary before microhardness measurements are taken?

3. What is the difference between Knoop Microhardness and Rockwell Hardness?

4. What can you say about the hardness of the indenter with respect to the material being tested? What indenter material (diamond or steel?) is appropriate to test silicon carbide?

5. Explain why hardness tester readings must be taken sufficiently far away from one another and away from the specimen edges.

6. What is etching and how does it work? Why is excellent sample preparation (a very flat, defect free surface) critical for imaging?

7. Briefly explain the processing of your samples (rolling and annealing).

8. What phases may be present in your samples and how may they contribute to properties?

9. How do you expect grain size to vary between samples and contribute to properties?

Answer 1

Sectioning of the test sample is performed carefully to avoid altering or destroying the structure of the material. Thus, if an abrasive saw is used, it is important to keep the sample cool with lubricant or coolant.

After the specimen is sectioned to a convenient size, it is mounted in a plastic or epoxy material to facilitate handling during the grinding and polishing steps. Mounting media must be compatible with the sample in terms of hardness and abrasion resistance.