Structural and mechanical properties of corundum and cubic (Al Cr1−)2+O3− coatings grown by reactive cathodic arc evaporation in as-deposited and annealed states

Abstract Coatings of (Al x Cr 1− x ) 2+ y O 3− y with 0.51 ⩽ x ⩽ 0.84 and 0.1 ⩽ y ⩽ 0.5 were deposited on hard cemented carbide substrates in an industrial cathodic arc evaporation system from powder-metallurgy-prepared Cr/Al targets in pure O 2 and O 2 + N 2 atmospheres. The substrate temperature and bias in all the deposition runs were 575 °C and −120 V, respectively. The composition of the coatings measured by energy dispersive X-ray spectroscopy and elastic recoil detection analysis differed from that of the facing targets by up to 11%. Microstructure analyses performed by symmetrical X-ray diffraction and transmission electron microscopy showed that corundum, cubic or mixed-phase coatings formed, depending on the Cr/Al ratio of the coatings and O 2 flow per active target during deposition. The corundum phase was promoted by high Cr content and high O 2 flow per target, while the cubic phase was observed mostly for high Al content and low O 2 flow per active target. In-situ annealing of the cubic coatings resulted in phase transformation from cubic to corundum, completed in the temperature range of 900–1100 °C, while corundum coatings retained their structure in the same range of annealing temperatures. Nanoindentation hardness of the coatings with Cr/Al ratio