Thick CrN/AlN superlattice coatings deposited by the hybrid modulated pulsed power and pulsed dc magnetron sputtering

Thick and dense CrN/AlN superlattice coatings (up to 10 mu m) have been deposited by a hybrid magnetron sputtering process from metallic Cr and Al targets, which were powered by modulated pulsed power (MPP) magnetron sputtering and middle frequency pulsed dc magnetron sputtering (PMS) techniques, respectively. The bilayer period (Lambda) of the coatings was changed from 10 to 2.5 nm by varying the ratio of the N-2 flow rate to the total gas flow rate. The microstructure and properties of the CrN/AlN coatings were characterized using electron probe microanalysis, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, scratch test, nanoindentation, and ball-on-disk wear test. The oxidation behavior of the thick CrN/AlN coating (Lambda = 2.8 nm) after annealing at 900 and 1000 degrees C in an ambient air has been investigated. Thick CrN/AlN coatings showed good adhesion. Superhardness values of 40-45 GPa and low wear rates in the low end of the 10(-8) mm(3) N-1 m(-1) range have been achieved in the coatings with A in a small range of 2.5 to 3.2 nm. No oxides were identified in the coatings after annealing at 1000 degrees C. The coating maintained cubic structure after annealing at 1000 degrees C. Published by Elsevier B.V.