Composition, Structure and Properties of the Cr1-xAlxN Hard Films Deposited by Arc Ion Plating

Four groups of Cr1-xAlxN films with different Al contents were deposited on ultrafine cemented carbide substrates by arc ion plating, their morphology, composition, phase structure and mechanical property were investigated via field emission scanning electron microscope, X-ray photo electron spectrometry, grazing incidence X-ray diffraction, nanoindenter and scratch tests. The results revealed that the thickness of the films is 1.28, 1.42, 1.64 and 1.79 mu m and the aluminum concentration x is 0.41, 0.53, 0.64 and 0.73, respectively, increased with incremental current of Al target. There is a close relationship between phase structure and composition. Films performed single centered cubic B1 structure when x is 0.41, however, demostrated mixed structure of c-(Cr,Al)N and hcp-AlN when x >= 0.53. The dimensions of grains obtained a minimum value of 8.9 nm near x=0.64, as Al content increasing, while the variation in hardness followed an increase-decrease pattern, reaching peak values of 35.3 GPa at x=0.64. The films performed pretty adhesion strength and their critical loads were all over 60 N. Based on all test results, the Cr1-xAlxN films exhibited the best combination properties including high hardness of 34.7 GPa, the highest elastic recovery coefficient of 57.4% and the best toughness while x is 0.53.