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Improvement of the electrochemical behavior of AISI 4140 steel substrate using [TICN/TINBCN]N multilayers system

Abstract:

The aim of this work is the improvement of the electrochemical behavior of 4140 steel substrate using TiCN/TiNbCN multilayered system as a protective coating. We have grown [TiCN/TiNbCN]n multilayered via reactive r.f. magnetron sputtering technique in which was varied systematically the bilayer period (Λ), and the bilayer number (n), maintaining constant the total thickness of the coatings. The coatings were characterized by (XRD), optical microscopy, electron microscopy (SEM) and transmission electron microscopy assisted with SAED-TEM. The electrochemical properties were studied by electrochemical impedance spectroscopy (EIS) and Tafel curves. XRD results showed a preferential growth in the FCC (111) crystal structure for [TiCN/TiNbCN]n multilayered coatings [1]. In this work was obtained the maximum corrosion resistance for the coating with (Λ) equal to 15 nm, corresponding to n = 200 bilayers. The polarization resistance and corrosion rate were around 8.6 kOhm·cm2 and 7.59·10-4 mmy, these values were 8.6 and 0.001 times higher, respectively, than that uncoated 4140 steel substrate (1.0 KOhm and 0.57 mmy). The improvement of the electrochemical behavior of the 4140 covered with this TiCN/TiNbCN multilayered system can be attributed to the presence of several interfaces that offers resistance of Cl- ions diffusion from the electrolyte toward the steel surface. © 2010 Nova Science Publishers, Inc. All rights reserved.