H. JIN et al.: CORROSION RESISTANCE OF CrAlVN COATINGS DEPOSITED ON PCrNi3Mo STEEL ...
591–597
CORROSION RESISTANCE OF CrAlVN COATINGS DEPOSITED
ON PCrNi3Mo STEEL SURFACES WITH REACTIVE MAGNETRON
SPUTTERING
KOROZIJSKA ODPORNOST CrAlVN PREVLEK, NANE[ENIH NA
POVR[INO JEKLA PCrNi3Mo Z REAKTIVNIM MAGNETRONSKIM
NAPR[EVANJEM
Hao Jin
1,2
, De-Yuan Li
2
, Hai-Jing Sun
3
, Lei Wang
3
, Ce-An Guo
1
, Gang Zhang
4
1
Shenyang Ligong University, School of Equipment Engineering, no. 6 Nanping Central Road, Hunnan New District,
Shenyang City, Liaoning Province, 110159, China
2
Shenyang University of Technology, School of Material Science and Engineering, no. 111 Shenliao West Road,
Economic & Technological Development Zone, Shenyang City, Liaoning Province, 110870, China
3
Shenyang Ligong University, School of Environmental and Chemical Engineering, no. 6 Nanping Central Road,
Hunnan New District, Shenyang City, Liaoning Province, 110159, China
4
Shenyang Ligong University, School of Material Science and Engineering, no. 6 Nanping Central Road, Hunnan New District,
Shenyang City, Liaoning Province, 110159, China
104310@163.com
Prejem rokopisa – received: 2017-12-07; sprejem za objavo – accepted for publication: 2018-04-16
doi:10.17222/mit.2017.210
CrAlN and CrAlVN coatings were deposited on the surfaces of PCrNi3Mo steel substrates using reactive magnetron sputtering.
The surface and cross-sectional morphology, hardness and elastic modulus, and crystalline-phase structure of the coatings were
characterized with scanning electron microscopy, nano-indentation and X-ray diffraction, respectively. Electrochemical testing
was employed for analyzing the corrosion resistance of the uncoated steel substrate and the substrates coated with the two pro-
tective materials. The results show that the average grain size of the CrAlVN coating is greater than that of the CrAlN coating,
and the hardness and elastic modulus of the CrAlVN coating (24.98 GPa and 336.02 GPa, respectively) are significantly greater
than those of the CrAlN coating (23.91 GPa and 316.2 GPa, respectively). The corrosion current densities of the CrAlN and
CrAlVN coated substrates are greater than that of the uncoated PCrNi3Mo steel by factors of about 4 and 100, respectively. The
electrochemical-reaction resistances of the CrAlN and CrAlVN coated substrates are greater than that of the uncoated steel by
factors of about 13 and 25, respectively. While both coatings provided a substantially improved corrosion resistance, the
CrAlVN coating performed better.
Keywords: magnetron sputtering, CrAlN coating, CrAlVN coating, corrosion resistance
Avtorji prispevka so CrAlN in CrAlVN prevleke nana{ali na povr{ino vzorcev iz PCrNi3Mo jekla s pomo~jo reaktivnega mag-
netronskega napr{evanja. Karakterizacijo povr{ine in preseka vzorcev, morfologijo, trdoto, elasti~ni modul in strukturo kristali-
ni~nih faz prevlek so izvedli z vrsti~nim elektronskim mikroskopom, nano-indenterjem (merilnikom trdote z vtiskovanjem trna
nano velikosti) in rentgensko difrakcijo. Elektrokemijske preiskave so izvedli zato, da bi analizirali korozijsko odpornost
vzorcev jekla s prevlekama v primerjavi z neprevle~enim materialom. Rezultati so pokazali, da je povpre~na velikost kristalnih
zrn CrAlVN prevleke ve~ja kot CrAlN prevleke. Trdota in elasti~ni modul CrAlVN prevleke (24,98 GPa oz. 336,02 GPa) sta
precej ve~ja od trdote in elasti~nega modula CrAlN prevleke (23,91 GPa oz. 316,2 GPa). Korozijski gostoti toka vzorcev z
obema prevlekama sta ve~ji kot je pri neprevle~enem PCrNi3Mo jeklu za faktor pribli`no 4 oziroma 100. Elektrokemi~na
reakcijska odpornost vzorcev, prevle~enih s CrAlN in CrAlVN, je v primerjavi z neprevle~enimi vzorci ve~ja za faktorje
pribli`no 13 oziroma 25. Ugotavljajo, da obe prevleki sicer zagotavljata znatno izbolj{anje korozijske obstojnosti jekla, vendar
je CrAlVN prevleka bolj{a.
Klju~ne beseda: magnetronsko napr{evanje, CrAlN prevleka, CrAlVN prevleka, odpornost proti koroziji
1 INTRODUCTION
The cost of artillery barrels is about 30–40 % of the
overall price of artillery tractors. The ablation and wear
of the inner gun barrel is the primary cause of the
gun-barrel failure. Consequently, a number of inner-bar-
rel treatments, such as laser treatment,
1–2
laser quenching
and Cr-composite finishing
3–5
were developed to improve
the service life of gun barrels by controlling their abla-
tion. Moreover, the deposition of anti-ablative coatings
on the inner barrel surface has been a strong focus of re-
search, and has included numerous coatings and meth-
ods, such as electroplated Cr,
6
sputtered Ta
7–9
and laser
Cr-composite processing,
10,11
in addition to the other
coatings applied, e.g., plasma surfacing
12
and chemical
vapor deposition.
13
At present, electroplated Cr is the
most widely adopted anti-ablative coating for improving
the service life of artillery barrels. However, the above
listed methods have so far failed to solve the problem of
gun-barrel ablation effectively. Moreover, the range, fir-
ing frequency and internal projectile speed of artillery
are constantly increasing, and the barrel ablation and
wear are correspondingly increasing as well. Conse-
quently, conventional Cr electroplating cannot meet the
Materiali in tehnologije / Materials and technology 52 (2018) 5, 591–597 591
UDK 67.017:620.193:621.793:669.058.6 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 52(5)591(2018)

present and developing requirements for artillery-barrel
lifetimes.
In addition to the ablation and wear of the inner gun
barrels in the process of combat use, artillery in marine
environments is subjected to corrosion during extended
periods in a non-combat state because sea water is rich in
chloride ions that lead to the local corrosion of metals.
Corrosion of the inner surfaces of gun barrels greatly ac-
celerates ablation during the service, which will corre-
spondingly accelerate the process of barrel failure, re-
sulting in greatly increased military expenses. Clearly,
the efforts to improve the service life of gun barrels by
controlling ablation must involve coatings with good cor-
rosion resistance. In addition to these concerns, the waste
liquid produced in the Cr-electroplating process is a
source of serious pollution problems.
14
In these respects,
CrAlN, which has been applied as a functional material
coating in various industrial fields, is an excellent candi-
date owing to its high hardness, excellent abrasion resis-
tance, excellent toughness, and good corrosion resis-
tance.
15–20
In particular, the good corrosion resistance is
provided by the active Cr element in the film, which
forms a dense Cr
2
O
3
surface-passivation layer.
In this paper, ternary CrAlN coatings were prepared
on the surfaces of the PCrNi3Mo steel using reactive
magnetron sputtering. In addition, quaternary CrAlVN
coatings were also prepared. The effects of doping with
V on the structure and mechanical properties of the
CrAlN coatings are discussed. The corrosion resistances
of the uncoated PCrNi3Mo steel substrate and the
substrates coated with the two protective materials were
evaluated in a 3.5 % of mass fractions of NaCl solution
with polarization-curve testing and electrochemical
impedance spectroscopy (EIS). This paper provides a
good reference for future research regarding the
service-life extension of artillery using CrAlN and
CrAlVN coatings deposited on the inner surface of gun
barrels with reactive magnetron sputtering.
2 EXPERIMENTAL PART
2.1 Experimental materials
The nominal chemical composition of the PCrNi3Mo
steel substrates is given in Table 1. The substrates were
subjected to wire cutting to produce samples with
dimensions of (15 × 15 × 3) mm. The samples were then
machined using a surface grinder and, successively,
polished with 400#, 600#, 800#, 1000#, 1500#, and
2000# SiC abrasive papers. The samples were then
successively polished with W2.5, W1.5 and W0.5
grinding pastes. The samples were subsequently cleaned
with acetone and alcohol for 10 min to remove oil from
the surfaces and then dried for 30 min in the sputtering
chamber. The sample pre-processing was conducted to
increase the adhesion between the coating and the
underlying steel substrate.
21
Table 1: Nominal chemical composition of PCrNi3Mo steel (wt%)
CM nS iC rN iM oVSP
0.4 0.41 0.25 1.28 3.14 0.37 0.20 0.001 0.012
2.2 Experimental methods
In the deposition experiments, Cr, Al and V targets
with a 99.95 % purity were employed in a
QHV-JGP400B II multi-target magnetron-sputtering unit
at a pressure of 6.0 × 10
–5
Pa. The rotational speed of the
substrate was 80 min
–1
, the substrate temperature was
350 °C, and the distance between the targets and sub-
strate was 60 mm. The Cr-target current was 0.2 A, the
V-target current was 0.07 A, and the Al-target power was
150 W. The sputtering time was 1 h for both coatings.
The hardness and elastic modulus of the coatings were
tested with nano-indentation using a G200 nano-in-
denter. The surface, cross-sectional morphology, and
composition of the coatings were investigated with scan-
ning electron microscopy (SEM) and energy dispersive
spectroscopy (EDS) using an SU8010 field emission
scanning electron microscope and an attached spectrom-
eter. The phase compositions of the coatings were deter-
mined with X-ray diffraction (XRD) using a
SHIMADZU XRD-7000 diffractometer with the Cu K
 source having a wavelength of 0.154056 nm, a scanning
diffraction angle in a range of 30–90°, a scanning step of
0.02°/s, and a scanning speed of 3°/min. A CHI660A
electrochemical tester was employed for analyzing the
sample corrosion. Electrochemical testing was conducted
using a three-electrode system where the saturated elec-
trode (SCE) was used as the reference electrode, 3.5 %
NaCl was used as the auxiliary electrode, and the analy-
sis medium and distilled water were used as the experi-
mental medium. The cell temperature was maintained at
25 ± 1°C using a constant-temperature water bath. Prior
to conducting voltammetry experiments, the working
electrode was polarized at –1 V for 2 min to remove any
oxide layer previously formed in air. The scanning speed
was 0.33 mV/s. During the measurements of the constant
potential-constant current (PG) transient response, the
working electrode was polarized at a constant potential
of –0.05 V for 15 min. When the electrode surface-
passivation current density attains a value of I
p
, the cur-
rent is switched to constant current control (i.e., a current
density set to 0.5 I
p
). At the moment of conversion, the
electrode potential is recorded when the current-density
change on the surface of the working electrode is –0.5I
p
.
3 RESULTS AND DISCUSSION
3.1 Microstructures of the CrAlN and CrAlVN coat-
ings
The surface morphologies of the as-deposited CrAlN
and CrAlVN coatings are shown by the SEM micro-
graphs presented in Figures 1a and 1b, respectively. We
note that the CrAlN coating surface exhibits a typical
H. JIN et al.: CORROSION RESISTANCE OF CrAlVN COATINGS DEPOSITED ON PCrNi3Mo STEEL ...
592 Materiali in tehnologije / Materials and technology 52 (2018) 5, 591–597

cauliflower morphology indicative of an aggregation of
fine, typically spherical particles into a collection of
larger particles of varying sizes. The shapes of the large
particles on the surface of the CrAlVN film are irregular
and the particles are tightly bonded. The surface of the
CrAlVN coating is flat and dense. The greater density
may be due to the introduction of V, which changed the
formation of atomic pairs or the nature of the atomic
group. The critical nuclei that form a stable size during
the sputtering changed the surface morphology relative
to that of the CrAlN coating.
Cross-sectional SEM micrographs of the as-deposited
CrAlN and CrAlVN coatings are shown in Figure 2,
which clearly reveals that both coatings are formed of a
typical columnar polycrystalline structure. We note that
the introduction of V increases the columnar crystal
density of the CrAlVN coating as well as the tendency of
the columnar crystals to become short-axis crystals. We
applied Digimizer software to evaluate the average
coating thickness based on five positions marked at the
junction of the fracture surface and the coating base. The
results show that the average thickness of the CrAlN
coating was 1.51 μm and that of the CrAlVN coating was
2.57 μm. Therefore, the deposition rate was increased
from 25.17 nm/min for the CrAlN coating to
42.83 nm/min for the CrAlVN coating, which represents
an increase of 17.68 %.
The XRD patterns of the as-deposited CrAlN and
CrAlVN coatings reveal that both CrAlN and CrAlVN
coatings have a single-phase cubic structure (NaCl type)
(Figure 3). No AlN can be observed in the hcp wurtzite
structure after the deposition. V tends to form a solid
solution in the CrAlN-based lattice rather than forming
an individual VN phase. Further, it can also be seen that
the addition of V significantly increases the (200)/(111)
diffraction-peak intensity ratio, which is indicative of the
preferred growth orientation related to the surface energy
and strain energy in the grain-growth process.
22–24
Coat-
ings with a face-centered cubic (fcc) structure tend to
grow in the direction of low strain energy to minimize
H. JIN et al.: CORROSION RESISTANCE OF CrAlVN COATINGS DEPOSITED ON PCrNi3Mo STEEL ...
Materiali in tehnologije / Materials and technology 52 (2018) 5, 591–597 593
Figure 3: XRD patterns of the two as-deposited coatings
Figure 2: SEM micrographs representing the cross-sectional morpho-
logies of: a) CrAlN and b) CrAlVN coatings
Figure 1: SEM micrographs representing the surface morphologies
of: a) CrAlN and b) CrAlVN coatings

the increase in the stress and strain during the growth.
The XRD results show that the growth of the coating
along the (111) direction is suppressed by the addition of
V. This indicates that the stress and strain in the interior
of the coating are not determined in the preferred
direction. Thus, the CrAlVN coating preferentially
grows along the (200) direction, which has the lowest
surface energy, and forms a fine-grain structure.
3.2 Hardness and elastic moduli of the CrAlN and
CrAlVN coatings
The hardness and elastic modulus of the uncoated
PCrNi3Mo steel substrate obtained with nano-indenta-
tion were 5.57 GPa and 258 GPa, respectively. The
hardness of the CrAlN coating in the as-deposited state
was 23.91 GPa. As a consequence of the solid-solution
strengthening, the as-deposited CrAlVN coating
obtained a higher hardness of 24.98 GPa. On the other
hand, the introduction of the stronger V–N bond as well
as the obstructed dislocation movement from the solid
solution, reveal a higher elastic modulus of 336 GPa for
CrAlVN compared to 316.2 GPa for CrAlN.
3.3 Corrosion resistance of the CrAlN and CrAlVN
coatings
The polarization curves of the uncoated PCrNi3Mo
steel substrate and the ubstrates coated with CrAlN and
CrAlVN films are shown in Figure 4. It can be seen from
the figure that the open-circuit potentials of the uncoated
steel substrate and CrAlN and CrAlVN coated substrates
(relative to the SCE) are –0.585 V, –0.382 V and
–0.211 V, respectively. The coatings obviously provide
different degrees of improvement in the corrosion
potential of the steel. From a thermodynamic point of
view, an increasing corrosion potential decreases the
likelihood of an electrochemical reaction. These results
indicate that both CrAlN and CrAlVN coatings increase
the corrosion resistance of the steel substrate, but only
the CrAlVN coating provides superior corrosion
resistance.
We note that the PCrNi3Mo steel exhibited active
dissolution in the 3.5 % NaCl solution. The anodic-pola-
rization current density of the steel increased very
rapidly with an increasing polarization potential, while
the anodic-polarization current density of the CrAlN
coated substrate increased more slowly, indicating an
increased corrosion resistance. In contrast, the polariza-
tion current density of the CrAlVN coated substrate
increased very slowly with the increasing polarization
potential, and exhibited little change after the transient
anodic dissolution of the anodic-polarized region above
the corrosion potential. These characteristics are
representative of passivation. The passivation current
density was about 1 μA/cm
2
. In addition, the cathodic-
polarization current densities of the CrAlN and CrAlVN
coated substrates were lower than that of the uncoated
steel substrate, indicating that the coatings suppressed
the cathode reaction of the material. Clearly, the
inhibition of the CrAlVN coating is more significant. In
a neutral solution, the cathode reaction of the uncoated
steel substrate is mainly the reduction of the oxygen
dissolved in water, which can be expressed as
2H
2
O+2O
2
+4e
–
= 4OH
–
(1)
The data obtained by fitting the polarization curves of
the three samples using CorrView are listed in Table 2.
Here, E
corr
is the corrosion potential, i
corr
is the corrosion
current density, b
c
is the cathode tangent slope, and b
a
is
the anode tangent slope. Generally, the self-corrosion
potential of a material is more negative, and the material
tends to be more aggressive. However, once the material
enters the corroded state, i
corr
becomes an important
index for the evaluation of the corrosion resistance of the
material where, with the increasing i
corr
, the corrosion
rate decreases, and, correspondingly, the corrosion
resistance increases. As can be seen from the table, the
value of i
corr
for the uncoated PCrNi3Mo steel substrate
in the 3.5 % NaCl solution was reduced from 6.55
μA/cm
2
to 1.66 μA/cm
2
and 0.066 μA/cm
2
for the CrAlN
and CrAlVN coated substrates, respectively. These
values represent the reductions in i
corr
by factors of about
4 and 100, respectively. These results further indicate
that the coatings improve the corrosion resistance of the
steel substrate, and that the corrosion resistance of the
CrAlVN coated substrate is superior.
Table 2: Results of fitting to the potentiodynamic curves from Figure 4
E
corr
(V vs.
SCE)
i
corr
(μA/cm
2
)
b c
(mV/
decade)
b
a
(mV/
decade)
Steel substrate -0.585 6.55 3.48 18.18
CrAlN coating -0.382 1.66 3.29 16.81
CrAlVN coating -0.211 0.066 6.14 4.04
As demonstrated with the results of electrochemical
testing, the PCrNi3Mo steel substrates with CrAlN and
H. JIN et al.: CORROSION RESISTANCE OF CrAlVN COATINGS DEPOSITED ON PCrNi3Mo STEEL ...
594 Materiali in tehnologije / Materials and technology 52 (2018) 5, 591–597
Figure 4: Potentiodynamic polarization curves of the PCrNi3Mo steel
substrate and the CrAlN and CrAlVN coated substrates in a 3.5 %
NaCl solution

CrAlVN coatings have good corrosion resistance in the
3.5 % NaCl solution. In addition, as discussed in
Subsections 3.1–3.3, the introduction of V provided for a
refined microstructure of the coating, leading to finer,
more uniform and dense-grain clusters than those of the
CrAlN coating, also enhancing its corrosion resistance.
25
The electrochemical impedance spectra for the
uncoated PCrNi3Mo steel substrate and CrAlN and
CrAlVN coated substrates are shown in Figures 5a to
5c, which represent the Nyquist plots, the Bode plots and
the phase angles versus frequency, respectively. The
radius of the impedance arc shown in the Nyquist plot
(Figure 5a) is representative of the corrosion resistance
of the material where the corrosion resistance increases
with the increasing radius. These results therefore verify
the results derived from the polarization curves, indi-
cating that the corrosion resistance of the steel substrate
in the 3.5 % NaCl solution is poor, while that of the
CrAlN coated substrate is considerably better, and that of
the CrAlVN coated substrate is even better. It can be
seen from the Bode plots (Figure 5b) that low-frequency
impedances (i.e., the absolute value of the impedance
|Z|) have the same order of magnitude, which again
demonstrates that the CrAlN coating and, particularly,
the CrAlVN coating improve the corrosion resistance of
the PCrNi3Mo steel in the 3.5 % NaCl solution.
The electrochemical impedance spectra for the three
samples were analyzed using the equivalent circuit
illustrated in Figure 6. Here, R
s
is the resistor that repre-
sents the solution resistance between the reference
electrode and the sample to be measured; R
po
is the
resistor that represents the layer resistance associated
with the barrier effect of the coating, and also the
protective effect of the corrosion product on the uncoated
steel substrate; CPE
po
is the capacitor that represents the
non-ideal capacitance associated with the coating; CPE
dl
is the capacitor that represents the non-ideal double-layer
capacitance associated with the metal-substrate reaction
under the coating; and R
ct
is the resistor that represents
the metal-coating interface reaction impedance. Using
pure capacitance, it is difficult to evaluate the actual
electrochemical process, particularly for solid-electrode
materials. Therefore, the phase angle of the original is
commonly used to replace the non-ideal capacitor. In
addition, CPE is used to represent the deviation of the
actual capacitance, which can be given as follows:
Z
Yj
n CPE
=
1
0
()  (2)
Here, Y
0
is the specific admittance (s
n
/ ·cm
2
);  is
the angular frequency (rad/s); and n is the dispersion
index, which indicates the degree of deviation from the
pure capacitance where n = 1 represents the ideal capaci-
tance, and n = 0 represents the pure resistance. The value
of n is generally close to 1, and represents the non-ideal
capacitance characteristics of the metal-coating interface.
The AC impedance data for the uncoated PCrNi3Mo
steel substrate and CrAlN and CrAlVN coated substrates
were fitted using the ZView software according to the
equivalent circuit shown in Figure 6, and the results are
listed in Table 3. The analysis of the fitted results reveals
details regarding the mechanism of the corrosion
resistance. The R
po
values obtained for the three mate-
rials are shown in Figure 7. Because the PCrNi3Mo steel
substrate has a much lower Cr content (1.28 % of mass
fractions) than the coating materials, a weak Cr
2
O
3
passivation layer is formed on its surface. Therefore, the
reported active-dissolution reaction mechanism
occurring in a salt solution containing corrosive Cl ions
26
may be similar to that of the general carbon steel in an
environment rich in Cl ions.
27
This forms loose corrosion
products on the surface that lack a reasonable protective
effect in the corrosive Cl-ion environment, which is
reflected by a very low value of 38.91  /cm
2
obtained
for R
po
. In contrast, the value of R
po
increased to 1333
H. JIN et al.: CORROSION RESISTANCE OF CrAlVN COATINGS DEPOSITED ON PCrNi3Mo STEEL ...
Materiali in tehnologije / Materials and technology 52 (2018) 5, 591–597 595
Figure 6: Equivalent electrical-circuit model
Figure 5: Electrochemical-impedance-spectroscopy results for the uncoated PCrNi3Mo steel substrate and CrAlN and CrAlVN coated sub-
strates: a) Nyquist plots, b) Bode plots, c) phase angle versus frequency

 /cm
2
after the steel substrate was coated with the
CrAlN film, and further increased to 4532  /cm
2
after
the coating with the CrAlVN film. This shows that both
coatings provided a good barrier effect, while the
CrAlVN coating was superior.
The R
ct
values obtained for the three materials are
shown in Figure 8. Based on the definition of R
ct
, larger
values of R
ct
represent a greater resistance to electro-
chemical reactions, making them less likely. As can be
seen from Table 3, the value of R
ct
increased from
14308  /cm
2
for the uncoated PCrNi3Mo substrate
material to 191,150  cm
-2
after the coating with a layer
of CrAlN, and further increased to 353850  /cm
2
after
the coating with a layer of CrAlVN. These figures repre-
sent increases in the value of R
ct
for the uncoated
substrate by factors of 13 and 25, respectively. The
characterization results and discussion clearly
demonstrate that the improved protective effect of the
CrAlVN coating is related to its more uniform and dense
microstructure.
4 CONCLUSIONS
This research investigated the preparation of CrAlN
and CrAlVN coatings on the surfaces of PCrNi3Mo steel
using reactive magnetron sputtering. The effects of
doping with V on the structure and mechanical proper-
ties of the CrAlN coatings were discussed. The corrosion
resistance of the uncoated PCrNi3Mo steel substrate and
the substrates coated with the two protective materials
was evaluated in a 3.5 % of mass fractions of NaCl
solution using polarization-curve testing and EIS. Based
on the results, the following conclusions can be drawn:
1) The hardness and elastic modulus of the CrAlN
coated steel substrates increased from 23.91 GPa and
316.2 GPa to 24.98 GPa and 336 GPa, respectively,
owing to the introduction of V into the CrAlN coat-
ing.
2) The PCrNi3Mo steel was dissolved in the 3.5 %
NaCl solution, and the corrosion products on its sur-
face demonstrated no protective effect.
3) The corrosion resistance of the PCrNi3Mo steel sub-
strates was enhanced by coating them with CrAlN
and CrAlVN films. The CrAlVN coating demon-
strated a superior protective effect, and a more ad-
vanced passivation phenomenon. The cathodic reac-
tion of the PCrNi3Mo steel substrate was suppressed
with the CrAlN and CrAlVN coatings.
4) The excellent corrosion protection of the CrAlVN
coating results from its uniform and dense micro-
structure.
Acknowledgment
This work was supported by the Shenyang Ligong
University Open Fund of Key Laboratory, Liaoning
Province, China (4771004kfs42).
5 REFERENCES
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H. JIN et al.: CORROSION RESISTANCE OF CrAlVN COATINGS DEPOSITED ON PCrNi3Mo STEEL ...
596 Materiali in tehnologije / Materials and technology 52 (2018) 5, 591–597
Table 3: Results of fitting the AC impedance data for the uncoated PCrNi3Mo steel substrate and CrAlN and CrAlVN coated substrates to the
equivalent electrical-circuit model from Figure 6
Sample
R s
( /cm
2
)
R po
( /cm
2
)
CPE po
R
ct
( /cm
2
)
CPE
dl
Y
0
(s
n
/ ·cm
2
)nY
0
(s
n
 ·cm
2
) n
Steel substrate 6.064 38.91 4.577×10
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0.84345 14308 5.272×10
-5
0.89505
CrAlN 4.294 1333 1.144×10
-6
0.91892 191150 1.185×10
-5
0.59965
CrAlVN 11.32 4532 5.788×10
-9
0.976 353850 2.666×10
-7
0.83379
Figure 8: Values of R
ct
for the uncoated PCrNi3Mo steel substrate and
CrAlN and CrAlVN coated substrates
Figure 7: Values of R
po
for the uncoated PCrNi3Mo steel substrate
and CrAlN and CrAlVN coated substrates

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H. JIN et al.: CORROSION RESISTANCE OF CrAlVN COATINGS DEPOSITED ON PCrNi3Mo STEEL ...
Materiali in tehnologije / Materials and technology 52 (2018) 5, 591–597 597