Cast cathodes and targets of Al–Cr–Nb–Si system for deposition of hardening nitride coatings

Abstract

The article describes a method for determining eutectic compositions of 3- and 4-component systems for obtaining cathodes and targets by casting. The eutectic compositions of the alloys in the ternary systems Al–Nb–Si, Cr–Nb–Si and the 4-component system Al–Cr–Nb–Si are calculated. The cathode of the eutectic composition (68Al8Cr4Nb20Si) at.%. was obtained by casting in a vacuum-induction furnace. The microstructure of the cathode material is investigated. Phase and elemental analysis are performed. The melting point of the alloy is determined by DSC (differential scanning calorimetry) and is 570 °C. The results of the research of hardening nitride coatings obtained by vacuum arc deposition in a nitrogen atmosphere are presented. The developed alloy of the Al–Cr–Nb–Si system of eutectic composition, namely (68Al8Cr4Nb20Si) at.% is used as a cathode. The dependence of the microhardness of the coatings on the pressure of nitrogen is determined. The microhardness of the coatings obtained at nitrogen pressure of 7 · 10–2 Pa reached 30 GPa. The phase composition of the coatings is investigated. All samples contain AlN, NbN, Si3N4 phases. The coefficient of friction of these coatings is 0.75–0.8. Cast cathode (68Al8Cr4Nb20Si) at.% can be an alternative to replace the currently used powder and composite cathodes.