Surface coatings on drill bits allow greater feeds and speeds when operating at higher temperatures, increasing tool life and thus productivity sometimes by 4 or 5 times.
TiAlN – Titanium Aluminium Nitride This coating has a greater hardness than TiN. A very thin film of AL203 (Aluminium Oxide) is formed on the surface of the TiAlN which greatly increases the service life of the tool, withstanding higher temperatures especially when machining Cast Iron and tough steels. Coatings are mostly effective at high speed rates when the temperature is sufficient for them to increase efficiency.