Class 2 materials include refractory and precious metals that, while having high melting points, are often soft and challenging to prepare metallographically. These materials tend to embed abrasives, deform easily, and contaminate subsequent steps. Careful abrasive selection and intermediate cleaning are critical to successful preparation.
Fractured SiC or loose abrasives can embed easily, especially in soft refractory metals.
Embedded particles can carry over between steps, introducing prep artifacts or cross-contamination.
Softness leads to surface smearing, masking microstructural detail without proper polishing.
Maintaining sharp edges during polishing is difficult; requires low-force polishing and careful cloth selection.
Use low-speed diamond wafering saws with coolant to prevent work hardening or surface drag.
Use castable resins to minimize heat and pressure. Edge retention is key for soft, valuable specimens.
Use alumina abrasives instead of SiC. Rinse and chemically etch between steps to remove embedded grit.
Finish with diamond or alumina on low-nap cloths. Use minimal pressure and short cycles to avoid smearing.
Check for clean, grit-free surfaces between steps
Verify microstructure clarity with minimal deformation
Ensure edge features are retained without rounding
Confirm no smear artifacts under magnification