Cutting tool coatings add hardness, heat resistance, and lubricity so a tool runs faster and lasts longer. The right coating depends mostly on how much heat the cut makes and whether the material likes to stick to the edge.
Common coatings at a glance
| Coating | Color | Max temp | Best for |
|---|---|---|---|
| Uncoated | Bright silver | — | Aluminum, brass, plastics; keeps the sharpest edge |
| TiN (titanium nitride) | Gold | ~1100°F | General purpose, mild steel, longer life than uncoated |
| TiCN (titanium carbonitride) | Blue-gray | ~750°F | Abrasive materials, cast iron; harder than TiN |
| TiAlN / AlTiN | Violet to black | ~1500°F+ | High heat: hardened steel, stainless, dry or high-speed cutting |
| ZrN (zirconium nitride) | Light gold | ~1000°F | Aluminum and non-ferrous; resists galling and sticking |
| DLC (diamond-like carbon) | Dark gray | ~750°F | Aluminum, copper, non-ferrous; very low friction |
| CVD diamond | Gray | ~1100°F | Graphite, carbon fiber, abrasive non-ferrous — never on steel |
Matching coating to the job
- Aluminum and non-ferrous: uncoated, ZrN, or DLC — they stay slick and resist built-up edge. Avoid coatings that promote sticking.
- Steel: TiN for general work, TiAlN when the cut runs hot or fast.
- Stainless and titanium: TiAlN or AlTiN, which form a heat barrier exactly where these alloys dump heat into the tool.
- Graphite and composites: CVD diamond for abrasion resistance — but never on steel, where diamond reacts and breaks down.
Max temperatures are approximate oxidation thresholds and vary by supplier and coating thickness.
Related: Feeds and Speeds Chart.