Strengthening mechanisms and thermal stability of arc deposited nanostructured TiAlN-based thin films

Titanium aluminium nitride (TiAlN)-based coatings are designed specially for applications where oxidation and wear resistance are primary demands, as in the case of cutting tools. Moreover the coatings are required to be thermally stable as well as have good "hot" hardness and fracture toughness for temperatures around 1000°C. Once these requirements are fulfilled, improved wear resistance is expected for standing extremely high shear forces developed on the tool rake face during high speed machining (HSM) in dry conditions. HSM also requires good shock resistance of coatings particularly demanding at the first second of the cutting process when the tool temperature has not reached "high temperature enhanced" plasticity. In this work, nanocrystalline films have been found to better respond to the complex paradox of conciliating high wear resistance with high fracture toughness. The synthesis of nanostructures with elevated mechanical properties became possible by using ultra high vacuum (UHV) deposition technologies such as cathode arc deposition. Compared to sputtering, for the same deposition conditions, arc permits to increase the average energy of particles extracted from the cathode. Moreover physical vapour deposition (PVD) techniques (Arc and Sputtering) permit to have good adherent coatings deposited at low temperature (