Synthesis and oxidation resistance of TiAlSiN and multilayer TiAlSiN/CrAlN coating

Oxidation resistant is one main factor to investigate for protective coatings of cutting tool application. In addition the formation of multilayer structure can be an alternative in improving the oxidation resistance. The monolayer TiAlSiN and multilayer TiAlSiN/CrAlN coating was deposited by cathodic arc ion-plating (AIP) method and oxidation resistance was studied in the range of 800 to 1000 °C. TiAlSiN with 10 at.% of Si added to TiAlN showed a cubic structured coating with a nanocomposite structure from transmission electron microscopy observation (TEM). Multilayer coatings with different periods, both showed uniform multilayer structure and measured period were 12.3 and 5.5 nm. The TiAlSiN/CrAlN coating of 5.5 nm showed superior oxidation resistance compared to monolayer TiAlSiN coating, with nitride coatings still existing even after 1000 °C. The additional amount of Al content of CrAlN to the TiAlSiN system prompt a formation of solid oxide layer of Al and Si-rich oxide on the top surface by forming a multilayer structure. In addition, the oxidation resistance was further improved for smaller period coatings. Its high number of interfaces and the crystal morphology of each layer worked as a barrier for oxygen inner diffusion and outer diffusion of metal contents to improve the oxidation resistance.