The substrate sets the ceiling on wear resistance and edge toughness. The coating decides the maximum cutting temperature and how much the workpiece material wants to stick to the edge. Neither can rescue a poor choice in the other, so they are selected together.
Carbide grades
| Grade | Grain size | Typical application |
|---|---|---|
| K10–K20 (micro-grain) | 0.6–0.8 µm | Aluminium, non-ferrous, graphite, reamers and drills |
| K20–K30 (sub-micron) | 0.4–0.6 µm | General steel milling, stainless, cast iron |
| K30–K40 (sub-micron) | 0.4–0.6 µm | Hardened steel, high-feed milling, interrupted cuts |
| K40+ (ultra-fine) | < 0.4 µm | 55–65 HRC finishing, superalloys, micro tools |
Coatings
| Coating | Hardness | Max working temp. | Where it earns its place |
|---|---|---|---|
| AlCrN | ~3,200 HV | 1,100 °C | Dry machining, hardened steel, general milling |
| AlTiN | ~3,300 HV | 900 °C | Hardened steel, high-feed, superalloys |
| TiAlN | ~2,800 HV | 800 °C | General purpose, drilling, broad material range |
| DLC | ~2,000 HV | 400 °C | Aluminium, copper and graphite — low adhesion |
| Uncoated | — | — | Aluminium finishing, composites, plastics |
How to choose
- Match the temperature first. If the cut runs hot — dry machining, hardened steel, high speed — take the coating with the higher working temperature.
- Then check adhesion. Aluminium and copper stick to hard coatings. DLC or uncoated is the answer there, not a thicker coating.
- Hardness last. A harder coating is not automatically better; a coating that chips off the edge is worse than a softer one that stays put.
- Consider the substrate together with the coating. An ultra-fine grade with a PVD coating is not the same tool as a coarser grade with the same coating.
Tell us the material and we will name the pair. If your workpiece is not in these tables, or the condition is unusual, describe it and we will answer with a substrate, a coating and starting cutting data.