Tribotechnical and mechanical properties of CrN/TiN multi-layer coatings deposited on the surface of die steel

The paper presents the results of studies of CrN/TiN multi-layer coatings on Cr12MoV cold work die steel deposited by vacuum-arc plasma-assisted method. All coatings were deposited at electric arc evaporator currents of 80 A for Ti and 90 A for Cr, substrate bias voltage (-) 150 V, substrate temperature 390-400 °C in a nitrogen-argon gas mixture (90 % (N2) and 10 % (Ar)) at a pressure of 0.6 Pa. The thickness of investigated coatings was about 4 µm. 8-, 16-, 32- and 64-layer CrN/TiN coatings were deposited, in which the thickness of each layer was 500 nm, 250 nm, 125 nm and 63 nm, respectively. The tribotechnical and mechanical properties of the deposited coatings were investigated. The microhardness of the CrN/TiN multi-layer coatings ranged from 16.4 GPa to 19.9 GPa, which was higher than the values for CrN and TiN single-layer coatings. Maximum microhardness was achieved for 16-layer CrN/TiN coating and amounted to 19.9 GPa. Changing the architecture of CrN/TiN multi-layer coatings by reducing the thickness of the CrN and TiN layers from 500 nm to 63 nm promotes a smooth decrease in both the wear parameter and the coefficient of friction. The minimum values of the wear parameter and the coefficient of friction were observed for the 64-layer CrN/TiN coating, which is 11 times and 2 times lower, respectively, than the average values for TiN and CrN single-layer coatings.