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Mechanical, tribological, and electrochemical behavior of Cr <inf>1-x</inf> Al <inf>x</inf> N coatings deposited by r.f. reactive magnetron co-sputtering method

Abstract:

Chromium aluminum nitride (Cr 1-x Al x N) coatings were deposited onto AISI H13 steel and silicon substrates by r.f. reactive magnetron co-sputtering in (Ar/N 2 ) gas mixture from chromium and aluminum targets. Properties of deposited Cr 1-x Al x N coatings such as compositional, structural, morphological, electrochemical, mechanical and tribological, were investigated as functions of aluminum content. X-ray diffraction patterns of Cr 1-x Al x N coatings with different atomic concentrations of aluminum (0.51 < x < 0.69) showed the presence and evolution of (1 1 1), (2 0 0), and (1 0 2) crystallographic orientations associated to the Cr 1-x Al x N cubic and w-AlN phases, respectively. The rate of corrosion of the steel coated with Cr 1-x Al x N varied with the applied power; however, always being clearly lower when compared to the uncoated substrate. The behavior of the protective effect of the Cr 1-x Al x N coatings is based on the substitution of Cr for Al, when the power applied to the aluminum target increases. The mechanical properties were also sensitive to the power applied, leading to a maximum in hardness and a reduced elastic modulus of 30 and 303 GPa at 350 W and a monotonic decrease to 11 and 212 GPa at 450 W, respectively. Finally, the friction coefficient measured by pin-on disk revealed values between 0.45 and 0.70 in humid atmosphere. © 2009 Elsevier B.V. All rights reserved.