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Corrosion resistance of a carbon-steel surface modified by three-dimensional ion implantation and electric arc

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The hybrid method of three-dimensional ion implantation and electric arc is presented as a novel plasma-ion technique that allows by means of high voltage pulsed and electric arc discharges, the bombardment of non-metallic and metallic ions then implanting upon the surface of a solid surface, especially out of metallic nature. In this study AISI/SAE 4140 samples, a tool type steel broadly used in the industry due to its acceptable physicochemical properties, were metallographically prepared then surface modified by implanting titanium and simultaneously titanium and nitrogen particles during 5 min and 10 min. The effect of the ion implantation technique over the substrate surface was analysed by characterization and electrochemical techniques. From the results, the formation of Ti micro-droplets upon the surface after the implantation treatment were observed by micrographs obtained by scanning electron microscopy. The presence of doping particles on the implanted substrates were detected by elemental analysis. The linear polarization resistance, potentiodynamic polarization and total porosity analysis demonstrated that the samples whose implantation treatment with Ti ions for 10 min, offer a better protection against the corrosion compared with non-implanted substrates and implanted at the different conditions in this study.
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Advances in Materials Research, Vol. 9, No. 1 (2020) 1-14
DOI: https://doi.org/10.12989/amr.2020.9.1.001
Copyright © 2020 Techno-Press, Ltd.
http://www.techno-press.org/?journal=amr&subpage=5 ISSN: 2234-0912 (Print), 2234-179X (Online)
Corrosion resistance of a carbon-steel surface modified by
three-dimensional ion implantation and electric arc.
E.D. Valbuena-Niño1, L. Gil 2, L. Hernández 2 and F. Sanabria 1
1 Foundation of Researchers in Science and Technology of Materials, Colombia
2 Universidad Nacional Experimental Politécnica, Puerto Ordaz, Venezuela
(Received December 13, 2019, Revised February 12, 2020, Accepted February 28, 2020)
Abstract. The hybrid method of three-dimensional ion implantation and electric arc is presented as a novel
plasma-ion technique that allows by means of high voltage pulsed and electric arc discharges, the bombardment of
non-metallic and metallic ions then implanting upon the surface of a solid surface, especially out of metallic nature. In
this study AISI/SAE 4140 samples, a tool type steel broadly used in the industry due to its acceptable
physicochemical properties, were metallographically prepared then surface modified by implanting titanium and
simultaneously titanium and nitrogen particles during 5 min and 10 min. The effect of the ion implantation technique
over the substrate surface was analysed by characterization and electrochemical techniques. From the results, the
formation of Ti micro-droplets upon the surface after the implantation treatment were observed by micrographs
obtained by scanning electron microscopy. The presence of doping particles on the implanted substrates were
detected by elemental analysis. The linear polarization resistance, potentiodynamic polarization and total porosity
analysis demonstrated that the samples whose implantation treatment with Ti ions for 10 min, offer a better protection
against the corrosion compared with non-implanted substrates and implanted at the different conditions in this study.
Keywords: carbon steel; corrosion; physicochemical properties; plasma technology; polarization
resistance; surface treatment
1. Introduction
AISI/SAE 4140 low content carbon steel also contains chromium, molybdenum, and
manganese as the main alloying elements. Such an atomic distribution allows it to achieve a
relatively high resistance to fatigue, abrasion, impact and torsion, and with an appropriate heat
treatment; can reach a high hardness. Additionally, the chromium content provides good
penetration resistance, and molybdenum offers high hardness and uniform wear resistance.
Because of the previously mentioned properties, AISI/SAE 4140 steel is broadly used in the
manufacture of components for automotive, construction, energy, among others industrial sectors
(Valbuena-Niño et al. 2016, Agüero 2007 and Soares et al. 2017).
It is well known that the most common problems that cause the damage of tools and industrial
parts, affecting operations, safety, maintenance and therefore costs; are corrosion and wear. For this
reason, finding alternatives that increase the performance of surfaces expose to physical and
Corresponding author, Ph.D., E-mail: deydannv@gmail.com
1
E.D. Valbuena-Niño, L. Gil, L. Hernández and F. Sanabria
chemical attack has been a developing subject of interest within the surface science and
engineering for materials protection. Enhancing corrosion resistance and wear by modification of
the microstructure and surface composition by mechanical, physical or chemical methods; can
imply a significant contribution that drives to energy saving by achieving higher efficiency and
yield of industrial processes (Winnicki et al. 2016, Jothi and Palanivelu 2016).
The surface modification generated by an hybrid of a high voltage pulsed and an electric arc
discharges at low pressures, consists in accelerating a flow of metallic and/or non-metallic ions
onto the surface of a solid material, where depending on the applied voltage magnitude, the ions
are deposited or embedded in the crystalline lattice causing a series of physical interactions that
affect the physical and chemical properties of the surface (Mussada and Patowari 2015, 2017,
Valbuena-Niño 2012).
This research proposes an evaluation of implanted AISI SAE 4140 steel substrates with
metallic (titanium) and non-metallic (nitrogen) species, against the corrosion by electrochemical
techniques. Polarization resistance and potentiodynamic polarization allows contrasting the effect
of treatment time on the corrosion resistance in implanted samples. Additionally, the changes
occurred on the surface structure and composition of the implanted substrates, are identified by
scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) characterisation
techniques. Experiments with a non-implanted reference substrates were also performed for
comparison purposes.
2. Experimental methods
The experimental methodology in this work was sequentially developed as follows: Substrates
preparation, definition of study conditions, ion implantation treatment and physicochemical and
electrochemical characterization.
2.1 Substrates preparation
Disk shape AISI/SAE 4140 steel coupons whose dimensions, 18mm in diameter and 3mm thick,
were implemented. Prior the implantation treatment, the surfaces to be expose were ground with
silicon carbide abrasive paper from 60 to 600 grit according with ASTM E3-11 Standard (2017),
then polished with alumina suspension of 1 μm, 0.3 μm, and 0.05 μm, and subsequently were
cleaned in an ultrasonic bath immerse in an ethanol solution for 30min as described by ASTM G1-
03 Standard (2017).
2.2 Surface treatment
The surface modification of AISI/SAE 4140 steel samples was carried out in the JUPITER
(Joint Universal Plasma and Ion TEchnologies Reactor), by exposing the coupons to Ti and Ti+N
atmospheres and activating a hybrid high voltage pulsed (HVP) and an electric arc discharges at
low pressure (Khvesyuk and Tsygankov 1997, Dulce-Moreno 2015, Dugar-Zhabon et al. 2012).
The ion implantation treatment on the substrates were carried out during 5 and 10 min. The
discharge parameters such as energy applied, pulse duration and frequency were established at 10
keV, 0.25 ms and 30 Hz respectively. The pulverization of the titanium cathode was performed
with an arc current of 140 A at a polarization potential of 19 V. The pressure during the Ti and
Ti+N treatment process were maintained at approximately 0.25 Pa and 1.00 Pa respectively. The
2
Corrosion resistance of a carbon-steel surface modified by
Fig. 1 Scheme of the substrates distributed in JUPITER
substrates, before the implantation treatment, were subjected to a sputtering process (generated
with a 5 keV pulsed electric discharge) in an argon atmosphere (Ar) for 15 minutes. Fig. 1 shows
the distribution of the arc electric system, whose cathode of Ti (at. 99.96%) was implemented; a
piezoelectric valve where the working gas (Nitrogen 99.99% purity) is fed into the chamber and
the location of the coupons (upon the HVP discharge cathode) inside JUPITER reactor. It is
noteworthy that the walls of the chamber will act as an anode during the ion implantation process.
(Dugar-Zhabon et al. 2002).
2.3 Surface topography
Characterization of the surface morphology of the implanted and non-implanted AISI/SAE
4140 specimens, were analysed by scanning electron microscopy (SEM). The surface topography
analysis was carried out by the scanning electron microscope FEI, model QUANTA FEG 650
environmental (ESEM). Likewise, to obtain the chemical composition and also verify the presence
of doping particles on the substrate surfaces, an x-ray energy dispersive spectroscopy (EDS) test
was performed together with optical emission spectroscopy technique by using a Bruker reference
spectrometer Q4 TASMAN.
2.4 Corrosion resistance
The corrosion resistance tests were performed with a Gamry Interface 1000
potentiostat/galvanostat, a standard cell composed of pH and temperature sensors, a nitrogen
bubbler and three electrodes. A calomel electrode as a reference, a graphite counter electrode
(auxiliary) and implanted and non-implanted AISI/SAE 4140 steel substrates as a working
electrode were prepared. A 3% NaCl solution was used as the electrolyte, and the open circuit
corrosion potential (Ecorr) was adjusted for one hour (1h) (ASTM G3 Standard 2014). The
corrosion rate (Vcorr) was obtained by the polarization resistance technique (Rp), with the
scanning of a ±20 mV potential at a scan rate of 0.1mV/s, around the corrosion potential (Ecorr).
3
E.D. Valbuena-Niño, L. Gil, L. Hernández and F. Sanabria
The anodic and cathodic slopes were acquired from potentiodynamic polarization with potential
sweep speed of 0.1 mV/s and potential range from -0.250 V to 1.6 V with subsequent Tafel
extrapolation at ±250 mV around corrosion potential (ASTM G5 Standard 014)
3. Results and discussions
The results obtained from the characterizations and electrochemistry test were carried out with
the purpose of evaluating the effect of ion implantation on ferrous alloys, identify changes on the
AISI/SAE 4140 steel surface and its performance against the corrosion.
3.1 Microstructure and composition of the material
Micrographs of an AISI/SAE 4140 steel surface were obtained from optical microscopy and
shown in Fig. 2. The metallographic analysis identified the formation of needle-type martensite
(grey phase) and ferrite (white phase) on the surface structure. The presence of such phases are
evidence of a quenching and tempering heat treatment during the manufacturing process of the
material.
The elemental atomic absorption analysis by arc spark allowed to obtain a percentage
composition of the constituent elements of the non-implanted and implanted substrates with Ti and
N ions. The results obtained in the Table 1 indicate that the samples correspond to alloy steel
whose chemical composition is similar to the values reported by ASTM A322 (2013). It is evident
that the implanted surfaces present an increase in the concentration of titanium and nitrogen
compared with the reference sample. Additionally, a direct correlation between the time of
treatment, the type of species or treatment and the composition of doping particles was identified.
3.2 Surface modification.
The superficial modification of AISI/SAE 4140 steel substrates were performing with Ti, and N
ions, where the surface modified with Ti exhibits a silver-coloured metallic shine, characteristic of
titanium while that treated with Ti+N ions present a golden metallic shine, indicating the
precipitation of titanium nitrides into the surface (see Fig. 3).
(a) Magnification to 500X
(b) Magnification to 1000X
Fig. 2 Surface of a AISISAE 4140 steel revealed with 2% nital
4
Corrosion resistance of a carbon-steel surface modified by
Table 1 Elemental chemical composition of implanted and non-implanted substrates
Element
Ti (5 min)
Ti (10 min)
Ti+N (5 min)
Ti+N (10 min)
C
0.451
0.435
0.456
0.442
Cr
0.935
0.889
0.922
0.909
Mo
0.196
0.199
0.201
0.213
Mn
0.667
0.639
0.650
0.605
Si
0.319
0.542
0.317
0.928
Cu
0.079
0.077
0.076
0.067
Bi
0.056
0.070
0.051
0.073
Ta
0.058
0.031
0.044
0.030
V
0.019
0.055
0.019
0.100
W
0.014
0.010
0.010
0.012
S
0.150
0.150
0.150
0.150
P
0.017
0.017
0.016
0.016
N
0.040
0.156
0.482
0.981
Ti
0.832
2.120
1.004
1.035
Fe
96.06
94.50
95.95
95.23
(a) Ti ions
(b) Ti + N ions
Fig. 3 Ion implantation: Post-treatment substrates
3.3 Surface analysis
The photomicrographs and spectra obtained by SEM and EDS illustrate the substrates surface
modified with Ti and N ions. The comparison between a non-implanted sample and Ti and Ti+N
implanted coupons are presented in Figs. 4, 5 and 6 respectively.
Fig. 4(a) shows the surface of the reference substrate (non-modified), where some irregularities
and small pitting are observed due to the surface sensitivity achieved by the decrease of the surface
area generated in the metallographic preparation. From the composition spectrum acquired by EDS,
the presence of the elements on the untreated surface, are shown in Fig. 4(b). As expected, a high
content (atomic percentage) of iron (88.77%) and the concentration values of other alloy elements
5
E.D. Valbuena-Niño, L. Gil, L. Hernández and F. Sanabria
(a) Surface micrograph of reference sample
(b) Composition spectrum
Fig. 4 Photomicrograph and spectrum of AISI SAE 4140 surface obtained by EDS
(a) Ti (5 min)
(b) Spectrum
(c) Ti (10 min)
(d) Spectrum
Fig. 5 SEM images and EDS Spectrums upon the implanted substrates
such as C (5.21%), Cr (1.41%), Mn (1.24%), Si (1.62%), S (0.93%) and P (0.82%) are in
agreement with those present in an AISI/SAE 4140 steel.
6
Corrosion resistance of a carbon-steel surface modified by
(a) Ti+N (5 mins) surface
(b) Spectrum Ti+N(5mins)
(c) Ti+N (10 mins)
(d) Spectrum Ti+N (10 mins)
Fig. 6 SEM images and EDS Spectrums upon the implanted substrates
From the photomicrographs of the surface of AISI/SAE 4140 steel modified with Ti (5 min)
and Ti (10 min) (Figs. 5(a) and 5(c) respectively) can be seen deformations (multiple micro-drops)
that appears due to the solidification of the evaporated material and the non-ionized Ti species
(clusters formed during the evaporation of the Ti cathode). This physical process could be
attributed to the operation conditions of the cathodic arc system implemented in the JUPITER
reactor for the evaporation of metals. The production of micro-droplets may be attributed to the
electric arc discharge does not ignite all over the surface of the cathode, which causes instability of
some spots called bright spot or cathodic spot which can be controlled from experimental
parameters such as the electric current. (Valbuena-Niño et al. 2011).
Elemental spectra obtained by EDS on the surface of the specimens treated with Ti (5 min) and
Ti (10 min) detected a titanium atomic percentage of 49.32% and 75.89% respectively, in addition
to the typical alloy elements presents in this type of carbon steel (see Figs. 5(b) and 5(d)). Such a
direct increase in the Ti concentration may be attributed to a longer exposition (for dose depends
on implantation time among other parameters) hence enabling more time to longer Ti ionized
particles to penetrate and then incorporate into the bulk, which profoundly disturbs the original
lattice (Sanabria et al. 2019).
The photomicrographs of the substrate surface of AISI/SAE 4140 steel surface modified with
Ti+N (5 min) and T+N (10 min) ions respectively, are presented in Figs. 6(a) and 6(c). The laminar
7
E.D. Valbuena-Niño, L. Gil, L. Hernández and F. Sanabria
shape that is appreciated in the structure, depends on the surface state obtained in the
metallographic preparation of the substrates. Additionally, a decrease of micro-droplets is shown in
comparison with that presented in Fig. 5 (surface modified with Ti ions). The decrease of
microdroplets present on the surface is due to the hybrid treatment involves the interaction of both
titanium and nitrogen particles by an electric arc discharge and a high voltage pulsed discharge
respectively with the substrate. The activation of these discharges with nitrogen ionized particles,
reduces the formation of Ti clusters produced by the electric arc discharge (Tsygankov et al. 2016).
As for the EDS results, the elemental composition spectra obtained on the modified specimen
surfaces with Ti+N for 5 min and 10 min are illustrated in the Figs. 6(b) and 6(d) respectively.
From the treatment with Ti+N (5 min), titanium composition were identified with 29.36% and
Nitrogen with 39.60% (in atomic percentage); while the treated substrates with Ti+N (10 min), the
atomic percentage of Ti and N detected was 30.43% and 30.73% respectively, results that are in
agreement with those reported in other works (Correa et al. 2008, Vladescu et al. 2004 and
Manory 1987).
3.4 Electrochemical tests
Table 2 presents the results obtained from the electrochemical tests of potentiodynamic
polarization and polarization resistance (Rp).
3.4.1 Potentiodynamic polarization
The potentiodynamic polarization is a very versatile technique, which gives information about
the active-passive behaviour of the system under study and also allows obtaining the Tafel (βa, βc)
slopes. Fig. 7 shows the curves of the anode and cathode branches of the non-implanted and
implanted substrates with Ti and Ti+N ions. It is important to emphasize that the corrosion
potential (Ecorr) provides the thermodynamic tendency of the system to corrode and that the more
positive the value, the lower the thermodynamic tendency to corrosion. In the potentiodynamic
polarization curves of the surface modified substrates only with Ti during 5 min and 10 min, the
Ecorr is found to be more positive than the corrosion potential of the non-treated and treated
samples with hybrid (Ti+N) treatment. On the order hand, the corrosion current density (icorr)
gives information about the kinetics of the corrosive process; the same can be related to the rate of
corrosion through Faradays law, the higher the icorr system, the higher the corrosion rate. In this
work, it was found that the icorr of systems surface modified with Ti (10 min) and Ti (5 min) is
smaller per an order of magnitude than the icorr of the non-modified substrate and the system
modified superficially with Ti+N (Table 2), indicating that the surfaces modified with titanium are
the most resistant to corrosion. Remarkably, the modified surfaces with Ti (10 min) are the most
resistant to corrosion followed by Ti (5 min), Ti+N (5 min), Ti+N (10 min) and those used as
Table 2 Potentiodynamic polarization and polarization resistance results
Treatment type
icorr (µA/cm2)
Ecorr (mV)
Rp ()
βa (mV/decade)
βc (mV/decade)
Vcorr (mpy)
Ti+N (10min)
3.7E+02
7.1E+02
5.4E+01
8.4E+01
1.5E+02
1.6E+02
Ti+N (5min)
3.0E+02
6.9E+02
5.7E+01
4.2E+01
1.5E+02
1.3E+02
Ti (10min)
3.4E+01
6.3E+02
1.2E+03
1.5E+02
7.2E+02
1.8E+01
Ti (5min)
1.3E+02
6.7E+02
1.7E+02
5.6E+01
1.3E+02
5.9E+01
No treatment
2.2E+03
6.4E+02
9.7
6.4E+01
1.0E+02
9.6E+02
8
Corrosion resistance of a carbon-steel surface modified by
Fig. 7 Curves of potentiodynamic polarization
a reference (see Table 2 and Fig. 7). A reason for this result is that Ti and the hybrid system Ti+N,
act as a diffusion barrier to prevent the transference of oxygen (among other oxidising agents)
during the oxidation process. Turning to the best corrosion resistance achieved in the Ti (10 min)
system by this electrochemical technique, it is interested to mention a correlation found between
the implantation time and the corrosion resistance where, as previously discussed, higher doses of
dopant particles reached in longer times will offer a better protection upon the surface of the
material as long as such a dose remain within the admissible range for this type of surface
treatment.
The anodic branch of the potentiodynamic polarization curve of the system surface modified
with Ti+N behaves similarly to the anodic branch obtained on the non-modified surface substrate,
which means that the treated surface with Ti+N was permeated by the corrosive medium with
greater ease compared to that modified with Ti. In Fig. 7, it is evidenced that the anodic curves of
all the evaluated surfaces did not present passive behaviours
3.4.2 Linear polarization resistance (LPR)
It is noteworthy that the larger the value of Rp, the lower the corrosion rate of the evaluated
surface. Considering that by increasing the total resistance of the system, is not easy to determinate
which of the contribution increases, but either the coating resistance generated by the layer of ions
implanted or by the charge transference, it is rising its anticorrosion protection. The obtained
results in Fig. 8(a) show that the surfaces implanted with Ti (10 min) seem to have the best
polarization resistance (Rp) with two orders of magnitude higher than the non-treated substrate,
and an order of magnitude greater than the surface modified system with Ti+N and Ti (5 min)
species. As for Fig. 8(b), it shows the Ecorr obtained by means of th Rp test, from which the
thermodynamic trend of the evaluated systems can be derived qualitatively. The results agree with
those obtained by the potentiodynamic polarization technique, i.e., the surface modified system
with Ti (10 min) has less tendency to corrode compared to the other evaluated surfaces.
The corrosion current density was calculated using Eq. (1) of Stern-Geary (Stern and Geary
1957).
9
E.D. Valbuena-Niño, L. Gil, L. Hernández and F. Sanabria
(a) Polarization resistance
(b) Corrosion potential
Fig. 8 Polarization electrochemical
   

(1)
From Eq. (1) βa and βc are the Tafel slopes obtained from potentiodynamic polarization tests.
The icorr presents the same behaviour as that found by the potentiodynamic polarization technique.
The implanted surface with Ti (10 min) demonstrated the best corrosion resistance. The corrosion
current density of the surfaces with Ti (10 min) is two orders of magnitude smaller than the icorr
of the non-treated substrate, and an order of magnitude smaller than the icorr of the surface
modified with Ti+N and Ti (5 min) (see Fig. 10(a)). In conclusion, all AISI/SAE 4140 steel
samples surface modified by ion implantation with metallic and non-metallic species, have higher
corrosion resistance compared to the non-treated reference substrate, revealing the beneficial effect
of the plasma-ion implantation technique in question.
The corrosion rate was calculated with the following Eq. (2).
    

(2)
From the Fig. 10(b), it can be seen how the corrosion rate of the non-implanted AISI/SAE 4140
steel substrate exceeds the corrosion rate of the other surface modified substrates with Ti and Ti+N
species, where the lowest corrosion rate was obtained by the surfaces modified with Ti (10 min).
Therefore, we can state that the surface modification performed by pulsed hybrid voltages of high
voltage and electric arc at low pressures in a Ti and Ti+N atmosphere is a technique capable of
improving the corrosion resistance of AISI/SAE 4140.
Titanium only surfaces have a better corrosion resistance compared to Ti+N treated specimens,
which is attributed, in the former, to the protective double layer (deposition and implantation) that
is formed on the surface of the substrate during the surface modification process, where much of
the titanium material evaporated by the cathodic arc discharge was deposited in the controlled
atmosphere during the ignition of the high voltage electric discharge. In the case of the Ti+N
modified system, it is possible that titanium nitride precipitation acts as a cathode and the steel
matrix as an anode, promoting micro galvanic corrosion, and as a consequence, the surface of the
10
Corrosion resistance of a carbon-steel surface modified by
(a) Current density
(b) Corrosion rate
Fig. 9 Corrosion parameters
substrate will preferentially corrode (Chang et al. 2016, Vasilescu et al. 2015). Additionally,
despite of offering a better protection than pristine samples, it has been reported that the effect of
nitrogen with titanium promotes the oxidation process by the presence of unbonded nitrogen.
These unbonded nitrogen atoms may accumulate at defect sites to form bubbles which are prone to
burst and therefore expose the surface to the chemical attack. (Karimi et al. 2002).
3.4.3 Total porosity
The porosity of a surface or coating is an important parameter studied in the corrosive
processes. The evaluation of the porosity by electrochemical methods is based on the ratio of the
current densities through the pores of the surface or layer under study (Liu et al. 2003). In the
present investigation, the total porosity (P) is obtained with Eq. (3), in agreement with the study by
Escobar et al. (2013) in layers of VN and HfN modified on AISI/SAE 4140 steel.
  

(3)
Where RpSubstrate is the polarization resistance of the substrate without surface modification, and
RpLayer is the polarization resistance of the modified layer-substrate. Table 3 shows the total
porosity coefficient in each of the evaluated surfaces.
When the value of the porosity is equal to the unit 1, it means that there is no type of barrier
between the corrosive medium and the substrate. When the porosity value is equal to zero 0, it
means that the modified layer acts as an effective barrier, with no porosity or defects. Table 3
shows that the value of the total porosity of the surface modified system with Ti (10 min) is in the
order of 10-3, that is, an order of magnitude lower than in the system modified Ti (5 min) and two
orders of magnitude below the porosity found on surfaces modified with Ti+N ions, which
Table 3 Porosity of the evaluated surfaces
Reference
Ti (10 min)
Ti (5 min)
Ti+N (10 min)
Ti+N (5 min)
1,0
8.3E-3
5.8E-2
1.8E-1
1.7E-1
11
E.D. Valbuena-Niño, L. Gil, L. Hernández and F. Sanabria
Table 4 The efficiency of evaluated surfaces in function of icorr and Rp.
Reference
Ti (10 min)
Ti (5 min)
Ti+N (10 min)
Ti+N (5 min)
icorr
0.0
98.5
93.9
83.1
Rp
0.0
99.2
94.2
81.8
means that the behaviour of the porosity is consistent with that obtained in the corrosion tests on
the evaluated surfaces. The less porous system presented better corrosion behaviour due to the
barrier effect that prevents the penetration of the corrosive electrolyte towards the substrate
structure.
3.4.4 Surface modification efficiency
The efficiency of the modified surface corresponds to the superficial and electrochemical
differences that exist between the treated and non-treated surfaces. Eqs. (4)-(5) calculated the
efficiency of the modified surfaces concerning the non-modified as a function of the icorr and the
Rp, in agreement with Escobar et al. (2013).
  
  


(4)
  
  


(4)
Table 4 shows the values of efficiency percentage of the evaluated surfaces as a function of
icorr and Rp. The surface modified substrates with Ti ions, present better efficiency than those
surface modified with Ti+N. The results indicate that surface modification with Ti and Ti+N ions
provide corrosion protection efficiency greater than 81%.
The efficiency values reported in Table 4, although maintaining the same trend, show that those
calculated as a function of Rp are slightly greater than those obtained from icorr. Therefore, the
difference presented between the two methods is due to possible alterations which are manifested
in the substrate of the modified systems when being polarized.
4. Conclusions
The treatments with Ti and N species by a hybrid high voltage pulsed and electric arc
discharges at low pressures, offered a surface protection against corrosion on AISI/SAE
4140 steel substrate with an efficiency between 81% and 99%. Therefore, surface
modification with Ti ions provides higher corrosion resistance in comparison with the
surface modified samples with Ti+N ions and the reference substrate without any treatment.
The lower porosity (P = 8.3 × 10-3) was obtained in the implanted samples with Ti ions for
10 mins, which was two orders of magnitude inferior to the porosity achieved by the hybrid
surface treatment with Ti+N ions.
The linear polarization resistance and potentiodynamic polarization results indicated that the
AISI/SAE 4140 steel surface modified with Ti ions during 10 min is the most effective
corrosion resistant treatment compared with the other treatments in this study.
12
Corrosion resistance of a carbon-steel surface modified by
The surface characterization by SEM showed that the existence of microdroplets on the
surface of AISI/SAE 4140 steel modified Ti ions, is more appreciable compared to those
treated with Ti+N ions. Elemental composition spectra obtained from EDS analysis,
detected the presence of Ti and N particles on the surface of AISI/SAE 4140 steel samples,
validating the effect of the metallic and non-metallic ions implantation on the microstructure
of ferrous alloys surfaces by the plasma-ion technique used in this study.
Acknowledgments
The authors acknowledge the sica y Tencnología del Plasma y Corrosión research group,
Laboratorio de Espectroscopía from Universidad Industrial de Santander and DIM-ETSI
Industriales from Universidad Politécnica de Madrid for the generous collaboration in the
acquisition of data and results.
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... Los métodos de fabricación de recubrimientos y de películas delgadas son importantes para adquirir diferentes desempeños de las estructuras dependiendo del objetivo funcional [1][2][3][4][5][6]. La tecnología de implantación iónica consiste en modificar las capas subsuperficiales de los materiales, mediante la influencia de iones de alta energía en la superficie, sin alterar las dimensiones geométricas ni las propiedades internas [7][8][9][10][11][12][13]. Las técnicas de deposición física en fase vapor (en inglés, physical vapor deposition-PVD), deposición química en fase a vapor (en inglés, chemical vapor deposition-CVD), entre otras, permiten la modificación de la superficie mediante la generación de sistemas de recubrimientos, monocapa, bicapa o multicapa, con características enfocadas a la optimización del desempeño funcional de la superficie [1][2][3][4][5][6]; por lo que, en la deposición por descarga de arco eléctrico en vacío un factor importante es la reducción del tamaño de las microgotas formadas en la superficie por las altas densidades de corriente que se presentan en el cátodo (spots) [3,4,7,[14][15][16]. ...
... Los métodos de fabricación de recubrimientos y de películas delgadas son importantes para adquirir diferentes desempeños de las estructuras dependiendo del objetivo funcional [1][2][3][4][5][6]. La tecnología de implantación iónica consiste en modificar las capas subsuperficiales de los materiales, mediante la influencia de iones de alta energía en la superficie, sin alterar las dimensiones geométricas ni las propiedades internas [7][8][9][10][11][12][13]. Las técnicas de deposición física en fase vapor (en inglés, physical vapor deposition-PVD), deposición química en fase a vapor (en inglés, chemical vapor deposition-CVD), entre otras, permiten la modificación de la superficie mediante la generación de sistemas de recubrimientos, monocapa, bicapa o multicapa, con características enfocadas a la optimización del desempeño funcional de la superficie [1][2][3][4][5][6]; por lo que, en la deposición por descarga de arco eléctrico en vacío un factor importante es la reducción del tamaño de las microgotas formadas en la superficie por las altas densidades de corriente que se presentan en el cátodo (spots) [3,4,7,[14][15][16]. ...
... Los recubrimientos fabricados mediante la descarga híbrida se obtienen en cuatro etapas fundamentales: (i) se produce el vapor de las especies metálicas neutras, átomos excitados, e iones multi-cargados, con la descarga arco eléctrico; (ii) se realiza la transferencia de flujos de vapor a la superficie del sustrato en condiciones de bajas presiones; en los procesos de deposición a baja presión se reducen las impurezas, se reducen las dispersiones y las colisiones por gas residual; (iii) se condensa el vapor en la superficie del sustrato, crecimiento atómico; (iv) se asiste el flujo de especies metálicas y no metálicas mediante la descarga de alto voltaje (10 kV), interacción de las microgotas con los iones energéticos por influencia de la descarga de alto voltaje (implantación iónica) [7][8][9][10][11][12]; la implantación iónica se puede utilizar como un proceso de activación de la superficie o para crear un sistema de capas subsuperficiales y superficiales que podría mejorar la interfaz superficie-capa y reducir el problema de adhesión del recubrimiento con la superficie del sustrato [7][8][9][10][11][12][18][19][20][21]. Las regularidades en la formación de microgotas son por causa del efecto de la inducción del campo magnético sobre la velocidad con la que se mueven los spots catódicos; lo que significa que cada uno de estos puntos debe ser considerado como una fuente de calor. ...
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... These interactions with such an aggressive media naturally Several studies have achieved interesting results in the implantation process and its applications in ferrous alloys, demonstrating that it is possible to modify the structural and chemical composition of materials in order to improve its performance in typical aggressive media in engineering applications [12][13][14][15][16][17][18][19][20]. ...
... Despite offering better protection than non-implanted samples, it has been reported that the effect of nitrogen with titanium implanted upon ferrous alloys, promotes anodic reactions owing to the presence of unbonded nitrogen. That is, unbonded nitrogen atoms may accumulate at defect sites to form bubbles that are prone to burst and therefore expose the surface to the chemical attack, reducing the protective properties against corrosion[19,39]. ...
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