Titanium Carbide (TiC)

Use diamond saw with continuous coolant flow. Diamond saws are essential for cutting hard ceramic materials. Standard diamond blade (0.3-0.5 mm thickness) is appropriate. Use adequate coolant flow to prevent overheating and minimize thermal shock. Cutting speed: 100-200 RPM for most diamond saws. Apply light to moderate pressure - the very hard material requires careful handling to avoid cracking. Avoid forcing the cut which can cause blade damage and sample cracking. Leave adequate allowance (~1-2 mm) for grinding away any damage from cutting.

Cold mounting with epoxy resin is preferred to avoid heat that could affect the microstructure. Use a low-shrinkage epoxy resin for best edge retention. Ensure complete cure before grinding to prevent edge rounding and maintain sample integrity. The very hard material requires careful handling during mounting to avoid cracking. For cutting tool and wear-resistant applications, ensure the mounting material provides adequate edge retention.

The very-hardness (3200 HV) of Titanium Carbide (TiC) requires careful grinding. Use standard SiC grinding papers with adequate water lubrication. Disc speed: 200-300 RPM. Apply light to moderate pressure (30-40 N per 30 mm sample) - the hard material may require longer grinding times. Use sharp, fresh grinding papers to minimize deformation.

Grinding sequence:

• 120 grit: Remove sectioning damage (40-90 seconds). Use moderate pressure to remove heat-affected zone.
• 240 grit: Remove previous scratches (40-90 seconds). Ensure complete scratch removal.
• 320 grit: Remove previous scratches (40-90 seconds). Ensure complete scratch removal.
• 400 grit: Remove previous scratches (40-90 seconds). Ensure complete scratch removal.
• 600 grit: Remove previous scratches (40-90 seconds). Ensure complete scratch removal.

Always rotate the specimen holder 90° between steps to ensure complete scratch removal. Use complementary rotation (platen and holder same direction, different speeds) rather than contra-rotation to minimize deformation. Adequate water lubrication is critical - avoid drying during grinding which can cause smearing.

The very-hardness requires careful polishing. Use diamond polishing with appropriate polishing pads for each stage. Apply light to moderate pressure throughout to prevent deformation.

Diamond polishing sequence:

• 6μm diamond: 2-4 minutes on a medium-hard synthetic pad (e.g., TEXPAN) with light to moderate pressure (30-40 N per 30 mm sample). Start with 6μm to minimize damage. The hard material may require longer polishing times.
• 3μm diamond: 2-4 minutes on a medium-hard synthetic pad (e.g., TEXPAN) with light pressure (25-35 N). Continue removing scratches from previous step.
• 1μm diamond: 2-3 minutes on a medium-hard synthetic pad with lighter pressure (25-35 N). These pads provide gentle material removal.
• 0.05μm colloidal silica: 1-2 minutes on a high-napped final polishing pad (e.g., MICROPAD) with very light pressure. This removes any remaining fine scratches and prepares the surface for etching. Monitor for relief - reduce polishing time if excessive relief develops.

Use appropriate polishing lubricants. The very-hard material means polishing times should be sufficient but not excessive - avoid over-polishing which can cause relief and affect grain boundary revelation. Monitor the surface frequently under the microscope to check for smearing or excessive relief.

Titanium carbide is chemically resistant but can be etched with HF-HNO₃ mixtures and Murakami's Reagent. For TiC-based cermets (TiC-Ni, TiCN-Ni), Murakami's is preferred as it attacks carbide phases while leaving the metallic binder bright. Murakami's Reagent - Standard etchant for TiC and TiC-based cermets:

• Composition: 10 g K₃Fe(CN)₆ + 10 g KOH + 100 ml water. Prepare fresh.
• Application: Immerse for 30 sec to 5 min at room temperature. For pure TiC, heating to 50–60°C may be needed.
• Reveals: TiC grain boundaries and carbide/binder phase distribution in cermets. TiC grains darken while Ni binder remains bright.
• Rinse: Water, then ethanol. Dry with warm air.

HF-HNO₃ Mixture - Chemical etchant for pure TiC:

• Composition: Dilute mixture of HF and HNO₃ (e.g., 10 ml HF + 30 ml HNO₃ + 60 ml H₂O).
• Application: Immerse for seconds to minutes at room temperature. Start with short times and check progress.
• Reveals: TiC grain boundaries. More aggressive than Murakami's.
• Rinse: Immediately with copious water, then ethanol. Dry with compressed air.

Thermal Etching - For grain boundary revelation without chemicals:

• Conditions: 1400–1600°C in vacuum or inert atmosphere (Ar) for 30–60 min. TiC oxidizes in air at high temperatures.
• Reveals: Grain boundaries by thermal grooving.

Etching Strategy:

• For TiC cermets, start with Murakami's Reagent for clear carbide/binder contrast
• For pure TiC, HF-HNO₃ or thermal etching may be needed
• Examine as-polished first — porosity and phase contrast may be visible

Safety: HF-HNO₃ contains hydrofluoric acid — extreme hazard requiring HF-rated PPE and calcium gluconate gel. Murakami's contains potassium ferricyanide — do NOT acidify. All work in fume hood.