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Novel performance in physical and corrosion resistance HfN/VN coating system

Abstract:

4140 steel substrates were coated with hafnium nitride/vanadium nitride multilayered with the objective of improving their corrosion resistance. The multilayered coatings were grown via a reactive r.f. magnetron sputtering technique by systematically varying the bilayer period (Λ) and the bilayer number (n) while maintaining constant the total coating thickness (~1.2μm). The coatings were characterized by X-ray diffraction (XRD), electron and transmission microscopy. The electrochemical properties were studied by Electrochemical Impedance Spectroscopy and Tafel curves. XRD results showed preferential growth in the face-centered cubic (111) crystal structure for [HfN/VN]n multilayered coatings. The best enhancement of the mechanical behavior was obtained when the bilayer period (Λ) 15nm (n=80) which yielded the highest hardness (37GPa) and elastic modulus (351GPa). The values for the hardness and elastic modulus are: 1.48 and 1.32 times greater than the coating with n=1, respectively. The maximum corrosion resistance was obtained for coatings with (Λ) equal to 15nm, corresponding to bilayer n=80. Polarization resistance and corrosion rate was around 112.19kΩcm2 and 0.094*10-3mmy respectively, these values were 172.6 and 0.007 times better than those shown by the uncoated 4140 steel substrate (0.65kΩcm2 and 0.014mmy, respectively). © 2013 Elsevier B.V.