A cutting tool coating is a thin PVD layer that raises surface hardness and thermal resistance while lowering friction.
TiAlN is the general-purpose workhorse for steel and cast iron, oxidizing at high temperature to form a protective alumina layer. AlCrSi and nanolayer coatings push hardness and heat resistance further for dry and high-speed machining. TiSi is preferred for non-ferrous and hard-ferrous combinations.
Choosing the right coating for your workpiece material and coolant strategy can add 2-5× tool life at no extra body cost.