Thermal Stability and Electrochemical Properties of Ti–Al–Mo–Ni–N Coatings Fabricated by Arc-PVD

The electrochemical properties of Ti–Al–Mo–Ni–N coatings with a molybdenum content of 20 and 25 at % fabricated by cathodic arc deposition (Arc-PVD) are studied. Series 2 coatings are characterized by the presence of Mo in both a chemically bound (Mo2N, as with series 1 coatings) and free states (i.e., metallic phase). Considering the multilayer architecture of coatings based on the mixed nitride (TiAl)N and molybdenum-containing phases, their corrosion destruction proceeds layer by layer due to different corrosion resistance of these phases in acidic and alkaline environments. Annealing the coatings at 600°C in vacuum gives rise to diffusional processes in them that lead to a growth of crystallites of the (TiAl)N nitride phase and a decrease in the microstrain. This phenomenon is considerably more conspicuous in series 2 coatings, which can be explained by the higher diffusivity of Mo atoms in the metallic phase than in the case of their counterparts in the nitride phase.