George’s Rules for Pain-free Specimen Preparation
- Use the gentlest possible sectioning equipment: abrasive cut off saw or precision saw only
- Use blades developed for metallography, not for production cutting
- Avoid shrinkage gaps when mounting
- Start grinding with the finest possible abrasive
- Keep the polishing surface uniformly covered with abrasive and lubricant
- Use proper loads
Revealing the Microstructure
- Nital and picralare good to assess the general structure
- Selective etchants are excellent for phase identification and measurements, e.g., alkaline sodium picrate to color cementite
- Prior-austenite grain boundaries in martensite can be revealed using aqueous saturated picric acid plus HCland a wetting agent at 80-90°C
- Color “tint” etchants reveal details about grain orientation, chemical segregation and residual deformation and are phase specific
- Choose the best illumination mode, e.g., dark field to reveal grain boundaries, polarized light for inclusions, and NomarskiDIC to reveal height differences between constituents that polish at different rates
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