CrNx and Cr1-xAlxN as template films for the growth of α-alumina using ac reactive magnetron sputtering

Crystalline alumina thin films were deposited on WC-Co substrates using a reactive inverted cylindrical ac magnetron sputtering technique with a chromium oxide prelayer. The interfacial prelayer of chromium oxide was prepared by controlled oxidation of CrNx and Cr1-xAlxN films deposited previously using the same ac reactive magnetron configured with one Cr and Al target. The oxidation was carried out by annealing CrNx and Cr1-xAlxN films in air at 973 and 1373 K, respectively. Scanning electron microscopy and energy dispersive x-ray microanalysis were carried out to investigate the thin film surface morphology and composition. The alumina coatings obtained on oxidized CrNx films (templates) were smooth and consisted primarily of κ and α phases. The diffraction peaks from the γ phase were not observed in any of the alumina coatings. The morphology and phase composition of the alumina coatings on the oxidized Cr1-xAlxN films (templates) were strongly dependent on the aluminum content in the films