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Aperador-Chaparro W.,University Militar Nueva Granada | Amaya C.,University of Valle | Amaya C.,Laboratorio Of Recubrimientos Duros | Bautista-Ruiz J.H.,University Francisco de Paula Santander
Revista Tecnica de la Facultad de Ingenieria Universidad del Zulia | Year: 2013

This paper presents the results variation of potential bias (0, -40, -60 and -100 V dc) of Al2O3 deposited on AISI 4140 steel substrates by magnetron sputtering method using a target DC reactive aluminum (99.9%) in an atmosphere composed of Ar/O2 to a substrate constant temperature of 300°C. The coatings were evaluated compared to corrosion, erosion and erosion-corrosion an impact angle of 90° and a solution of 0.5 M NaCl and silica, analyzing the effect of potential bias (0, -40, -60 and -100 V dc) Al2O3 coatings. The electrochemical characterization was performed using the technique of electrochemical impedance spectroscopy (EIS), optical microscopy (OM) was used to determine the morphology after the electrochemical evaluation. Nyquist diagrams for dynamic corrosion and erosion corrosion show a capacitive behavior with a high impedance module and two time constants. By decreasing the potential bias was generated an increased resistance to polarization, both for mechanisms dynamic corrosion and corrosion erosion. Source


Caicedo J.C.,University of Valle | Amaya C.,University of Valle | Amaya C.,Laboratorio Of Recubrimientos Duros | Cabrera G.,University of Valle | And 4 more authors.
Thin Solid Films | Year: 2011

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 (∼ 3 μm). The coatings were characterized by X-ray diffraction (XRD), optical microscopy, electron microscopy and transmission electron microscopy assisted with selected area electron diffraction. The electrochemical properties were studied by Electrochemical Impedance Spectroscopy and Tafel curves. XRD results showed a preferential growth in the face-centered cubic (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 bilayered. The polarization resistance and corrosion rate were around 8.6 kOhm cm2 and 7.59 • 10- 4 mm/year, these values were 8.6 and 0.001 times better than those showed by the uncoated 4140 steel substrate (1.0 kOhm and 0.57 mm/year), respectively. The improvement of the electrochemical behavior of the 4140 coated with this TiCN/TiNbCN multilayered system can be attributed to the presence of several interfaces that act as obstacles for the inward and outward diffusions of Cl- ion species, generating an increment in the energy or potential required for translating the corrosive ions across the coating/substrate interface. Moreover, the interface systems affect the means free path on the ions toward the metallic substrate, due to the decreasing of the defects presented in the multilayered coatings. © 2011 Elsevier B.V. All rights reserved. Source


Moreno H.,Laboratorio Of Recubrimientos Duros | Caicedo J.C.,University of Valle | Amaya C.,University of Valle | Munoz-Saldana J.,CINVESTAV | And 3 more authors.
Applied Surface Science | Year: 2010

The aim of this work is to improve the mechanical properties of AISI 4140 steel substrates by using a TiN[BCN/BN]n/c-BN multilayer system as a protective coating. TiN[BCN/BN]n/c-BN multilayered coatings via reactive r.f. magnetron sputtering technique were grown, systematically varying the length period (Λ) and the number of bilayers (n) because one bilayer (n = 1) represents two different layers (tBCN + tBN), thus the total thickness of the coating and all other growth parameters were maintained constant. The coatings were characterized by Fourier transform infrared spectroscopy showing bands associated with h-BN bonds and c-BN stretching vibrations centered at 1400 cm-1 and 1100 cm-1, respectively. Coating composition and multilayer modulation were studied via secondary ion mass spectroscopy. Atomic force microscopy analysis revealed a reduction in grain size and roughness when the bilayer number (n) increased and the bilayer period decreased. Finally, enhancement of mechanical properties was determined via nanoindentation measurements. The best behavior was obtained when the bilayer period (Λ) was 80 nm (n = 25), yielding the relative highest hardness (∼30 GPa) and elastic modulus (230 GPa). The values for the hardness and elastic modulus are 1.5 and 1.7 times greater than the coating with n = 1, respectively. The enhancement effects in multilayered coatings could be attributed to different mechanisms for layer formation with nanometric thickness due to the Hall-Petch effect; because this effect, originally used to explain increased hardness with decreasing grain size in bulk polycrystalline metals, has also been used to explain hardness enhancements in multilayered coatings taking into account the thickness reduction at individual single layers that make up the multilayered system. The Hall-Petch model based on dislocation motion within layered and across layer interfaces has been successfully applied to multilayered coatings to explain this hardness enhancement. © 2010 Elsevier B.V. All rights reserved. Source


Nieto J.,Laboratorio Of Recubrimientos Duros | Caicedo J.,University of Valle | Amaya C.,Laboratorio Of Recubrimientos Duros | Amaya C.,University of Valle | And 4 more authors.
DYNA (Colombia) | Year: 2010

Niobium Nitride (NbN) and Aluminum Niobium Nitride (AlNbN) thin films were deposited on silicon (100) and steel AISI 4140 substrates through a multitarget r.f. (13.56 MHz) magnetron sputtering system. The target where made using 4N purity Nb and Al and the growth was performed under a gas mixture of Ar/N2, for different substrate polarization voltages, in order to study the effect of polarization voltage on the crystalline structure and electrochemical properties. Steel 4140 is widely used for fabrication of machines components with hardness between 28 and 38 Rockwell C, however life time of this steel is limited by its low wear and corrosion resistance. The XRD pattern of the sample showed predominantly Bragg peaks for the planes (200) corresponding to FCC phase of the AlNbN, hexagonalδ' NbN phase and hexagonal AlN phase. The FTIR analysis showed vibrational modes associated with NbN, AlN and AlNbN bounds. The steel AISI 4140 with and without AlNbN coating were characterized through electrochemical impedance spectroscopy (EIS) and Tafel polarization curves. As a result of this work it was found a voltage polarization dependence on speed corrosion for NbN and Al-Nb-N films. Source


Moreno H.,Laboratorio Of Recubrimientos Duros | Caicedo J.C.,University of Valle | Amaya C.,Laboratorio Of Recubrimientos Duros | Amaya C.,University of Valle | And 4 more authors.
Diamond and Related Materials | Year: 2011

The aim of this work is to improve the electrochemical behavior of AISI 4140 steel substrates by using a TiN[BCN/BN]n/c-BN multilayer system as a protective coating. We grew TiN[BCN/BN]n/c-BN multilayers via reactive r.f. magnetron sputtering technique, systematically varying the length period (Λ) and the bilayer number (n), maintaining constant the total thickness of the coating and all other growth parameters. The coatings were characterized by FTIR spectroscopy that showed bands associated to h-BN bonds, and c-BN stretching vibrations centered at 1385 cm- 1 and 1005 cm- 1, respectively. Film composition was studied via X-ray photoelectron spectroscopy where typical signals for C1s, N1s and B1s are shown. The electrochemical properties were studied by electrochemical impedance spectroscopy and Tafel curves. In this work, the maximum corrosion resistance for the coating with (Λ) equal to 80 nm was obtained, corresponding to n = 25 bilayers. The polarization resistance and corrosion rate were around 10.1 kOhm cm2 and 0.22 mm/year; these values were 83 and 15 times higher, respectively, than uncoated AISI 4140 steel substrate (0.66 kOhm cm2 and 18.51 mm/year). Optical microscopy was used for surface analysis after corrosive attack. The improvement of the electrochemical behavior of the AISI 4140 coated with this TiN[BCN/BN]n/c-BN multilayer system can be attributed to the presence of several interfaces that offer resistance to diffusion of Cl- of the electrolyte toward the steel surface. © 2010 Elsevier B.V. Source

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