Abstract:

Ti-N/Al-Si-N coatings deposited by arc-PVD method using a cathodic vacuum arc evaporation apparatus is characterized by multilayer structure that corresponds to alternating layers of crystalline TiN with variable stoichiometry and amorphous Si3N4 with inclusions of hexagonal AlN grains. The thickness of the layers was 5–20 nm. The structure of coatings was regulated by rotation speed of the samples coated (n) in relation to evaporated cathodes and substrate bias voltage (Ub). The multilayer structure was not observed at the minimal energy of evaporated particles which is determined by the minimal Ub=-60 V. Its separate areas were only observed in a limited volume of deposited coating. The grain structure of coatings was extremely heterogeneous. The distinct multilayer structure of coating with clear interphase boundary was formed when increasing Ub up to -120 V. The reducing of layers thickness and corresponding grains were observed. The subsequent increase of Ub up to -140 V leads to formation of sublayers 2–3 nm thick within the layers ~15 nm thick. The increase of n from 2 to 4 revs per minute at a constant Ub led to decrease the layer thickness in 2.5 times. The increasing of layer boundaries length and refinement of coatings grain structure are accompanied by increase of hardness from 33 to 56 GPa. During scratch test the coatings were destructed according to the cohesion mechanism. The complete abrasion of the coating to the substrate was not observed up to load 90 N.