Mechanical properties and microstructural evolution of TiN coatings alloyed with Al and Si

TiN coatings have been widely used as hard coating on cutting tools, but the poor oxidation resistance at temperatures above 500 °C created an interest in ternary coatings, e.g., Ti–Al–N and Ti–Si–N due to their improved hardness and high-temperature oxidation resistance. Here, we present a comparative research on the Ti–X–N (X = Al or Si) coatings deposited onto cemented carbide substrates by cathodic arc evaporation. The incorporation of Al and Si into TiN coating results in an increase in hardness, thermal stability and cutting performance. Compared to TiSiN coated inserts, TiAlN coated inserts show similar performance during continuous turning of stainless steel at the cutting speed of 160 m/min, but worse performance at the higher cutting speed of 200 m/min. However, during milling of steel, TiAlN coated inserts perform better than TiSiN coated inserts.