Features of the Formation of Coatings Based on the Ti–Al–N System from Separated Flows of Cathode-Arc Plasma

Abstract

The influence of technological parameters of deposition from separated flows of cathode-arc plasma during simultaneous sputtering of metal cathodes of titanium and aluminum (arc discharge currents on the cathodes, bias potential on the substrate, and reaction gas pressure) on the elemental and phase composition, as well as the properties of coatings of the Ti–Al–N system, was studied. Varying the aluminum content in the multicomponent coating Al/(Al + Ti) from 13 to 67 at % by changing the discharge current of titanium and aluminum at a bias potential of –80 V leads to the evolution of the phase composition of the coatings from a homogeneous solid solution based on (Ti,Al)N to a mixture of phases TiN, AlN, and Ti₃AlN. Reducing the bias potential on the substrate to –60 V in the same aluminum concentration range results in the formation of coatings, which are characterized by a change in phase composition from a (Ti,Al)N solid solution to a two-phase solution based on (Ti,Al)N phases and hexagonal nitride Ti₃Al₂N₂. It has been shown that the maximum value of nanohardness of coatings, equal to 38 GPa, is observed when the hexagonal Ti₃Al₂N₂ phase (with the Al/(Al + Ti) ratio = 55 at %) is formed in their composition. An increase in the proportion of aluminum Al/(Al + Ti) in the coating to 67 at % leads to a decrease in their nanohardness to 12 GPa, which is due to both an increase in the proportion of aluminum in the coating and a change in its phase composition from the solid solution (Ti,Al) N to a mixture of TiN, AlN, and Ti₃AlN phases. It has been established that the best corrosion resistance is characterized by coatings with an aluminum content Al/(Al + Ti) from 28 to 45 at %, as evidenced by the low values of anodic dissolution currents at the positive values of corrosion potentials.