Machining performance of Ti–Al–Si–N coated inserts

Ti–Al–Si–N quaternary coating has recently been developed for industrial applications due to its excellent machining performance. Here, we present a comparative research on Ti–Al–N single layer, Ti–Al–Si–N single layer, TiAlN–TiAlSiN bilayer and TiAlN/TiAlSiN multilayer coatings deposited onto cemented carbide substrates by cathodic arc evaporation. The incorporation of Si into the Ti–Al–N coating results in an increase in hardness and thermal stability due to the formation of nanocomposite nc-TiAlN/a-Si3N4, and thereby causes an improved performance during continuous cutting. However, the lower toughness and adhesive strength with a substrate reduce its cutting-life during milling. Further optimization of Ti–Al–Si–N coated inserts during milling can be obtained by a structure adjustment from the nanocomposite into TiAlN–TiAlSiN bilayer and TiAlN/TiAlSiN multilayer coatings, which causes an increase to 156% and 172% for the life-time of Ti–Al–Si–N coated inserts, respectively. Our results indicate that the machining performance of coatings containing Si in both continuous cutting and milling can be optimized by the structure design of the TiAlN/TiAlSiN multilayer, where the coating sustains a high hardness of the Ti–Al–Si–N coating combined with a good cohesive strength with the substrate similar to the Ti–Al–N coating.