Why Coating Matters: Heat & Lubricity
Carbide starts to lose hardness at ~800°C. Modern High Speed Machining generated temps of 1000°C+. The coating acts as a thermal barrier. Pushing heat into the chip instead of the tool.
TiN (Titanium Nitride)
Color: Golden
The classic "Gold" coating. Good for general purpose mild steel and old HSS tools. Low heat resistance (600°C). Obsolete for modern hard milling.
TiCN (Titanium Carbonitride)
Color: Violet / Grey
Harder than TiN. excellent lubricity. Great for Tapping and Aluminum (if thin). Moderate heat resistance.
AlTiN (Aluminum Titanium Nitride)
Color: Dark Grey / Black / Blue-ish
The modern standard for steel and stainless. High Aluminum content forms an Aluminum Oxide skin when hot, protecting the tool. Works BEST when hot (>800°C). Do not use with coolant on hard steels (thermal shock).
ZrN (Zirconium Nitride)
Color: Pale Gold / Champagne
The king of Aluminum applications. Extremely high lubricity prevents "Built Up Edge" (BUE) where aluminum welds to the cutter.
Aluminum: The "No AlTiN" Rule
NEVER use AlTiN (Black) coatings on Aluminum.
Aluminum has a chemical affinity for Aluminum. The Aluminum in the chip will friction-weld to the Aluminum in the coating. Use Uncoated (Polished) or ZrN / DLC for aluminum.
Related Calculators
Open a calculator when coating choice changes heat limits, chip load targets, or the final spindle-speed window for the job.
Set RPM and feed after choosing a coating that matches the work material and heat profile.
Validate feed per tooth when coating, flute geometry, and cutter material change the safe chip thickness.
Translate coating-driven SFM limits into spindle speed before you release the program.