Hardness and elastic modulus of titanium nitride coatings prepared by PIRAC method

Abstract

In the present work, hardness and elastic modulus of a titanium nitride coatings prepared on Ti6Al4V by powder immersion reaction-assisted coating (PIRAC) are tested and comparatively studied with a physical vapor deposition (PVD) TiN coating. Surface hardness of the PIRAC coatings is about 11GPa, much lower than that of PVD coating of 22GPa. The hardness distribution profile from surface to substrate of the PVD coatings is steeply decreased from ∼22GPa to ∼4.5GPa of the Ti6Al4V substrate. The PIRAC coatings show a gradually decreasing hardness distribution profile. Elastic modulus of the PVD coating is about 426GPa. The PIRAC coatings show adjustable elastic modulus. Elastic modulus of the PIRAC coatings prepared at 750∘C for 24h and that at 800∘C for 8h is about 234 and 293GPa, respectively.对采用粉末埋入反应辅助涂层（PIRAC）在Ti6Al4V表面制备的氮化钛涂层的硬度和弹性模量进行了测试，并与物理气相沉积（PVD）TiN涂层进行了对比研究。其中涂层的模量采用弯曲法测试计算得到。分别采用对抛光后断面进行腐蚀后再观测和直接抛光断面元素的能谱（EDS）分析进行涂层厚度测量。PIRAC涂层从表面到基体的氮分布逐渐减少，分别对应TiN、Ti2N和Ti（N）固溶体相。PIRAC涂层的表面硬度约为11GPa，远低于PVD涂层的22 GPa。PVD涂层表面到基体的硬度分布从Ti6Al4V基体的约22 GPa急剧下降到约4.5 GPa。PIRAC涂层的硬度分布曲线则是由表及内逐渐减小。PVD涂层的弹性模量约为426GPa。PIRAC涂层的弹性模量可调。750ºC 处理 24 h 和 800ºC 处理8 h制备的PIRAC涂层的弹性模量分别约为234GPa和293GPa。进一步分析探讨了2种涂层硬度、模量差异的原因及其影响。

Full text

HARDNESS AND ELASTIC MODULUS OF TITANIUM
NITRIDE COATINGS PREPARED BY PIRAC METHOD
SIYUAN WU
*
, SHOUJUN WU
*
,
§
, GUOYUN ZHANG
†
and WEIGUO ZHANG
‡
*
College of Water Resources and Architectural Engineering,
Northwest A&F University,
Yangling Shaanxi 712100, P. R. China
†
State Key Laboratory of Crop Stress Biology for Arid Areas,
Northwest A&F University,
Yangling Shaanxi 712100, P. R. China
‡
College of Mechanical and Electronic Engineering,
Northwest A&F University,
Yangling Shaanxi 712100, P. R. China
§
shoujun_wu@163.com
Received 13 December 2016
Revised 6 May 2017
Accepted 19 May 2017
Published
In the present work, hardness and elastic modulus of a titanium nitride coatings prepared on
Ti6Al4V by powder immersion reaction-assisted coating (PIRAC) are tested and comparatively
studied with a physical vapor deposition (PVD) TiN coating. Surface hardness of the PIRAC
coatings is about 11 GPa, much lower than that of PVD coating of 22 GPa. The hardness distri-
bution pro¯le from surface to substrate of the PVD coatings is steeply decreased from 22 GPa to
4.5 GPa of the Ti6Al4V substrate. The PIRAC coatings show a gradually decreasing hardness
distribution pro¯le. Elastic modulus of the PVD coating is about 426 GPa. The PIRAC coatings
show adjustable elastic modulus. Elastic modulus of the PIRAC coatings prepared at 750C for 24 h
and that at 800C for 8 h is about 234 and 293 GPa, respectively.
Keywords: Titanium nitride; coating; PIRAC method; elastic modulus; hardness.
1. Introduction
Ti alloys, e.g. Ti6A14V, o®er the best combination of
properties and biocompatibility of all structural im-
plant metals.
1
Unfortunately, Ti- alloys have low wear
resistance and cannot be used in articulating compo-
nents of total joint replacements (TJR), demanding
surface improvement on its mechanical and tribologi-
cal properties. Given high hardness (Hv 25 GPa) and
excellent biocompatibility, titanium nitride has lat-
terly received considerable attention as wear resis-
tance coating for orthopedic endoprostheses.
2–4
The abrasion behavior (and thus abrasion rate) of
ceramic materials is dependent upon the relative
hardness of the abrasive and the material being
worn.
5,6
The elastic modulus (Young's modulus) of
materials is a measure of the interatomic bonding
forces. The elastic modulus is necessary for evaluation
§
Corresponding author.
Surface Review and Letters, Vol. 25, No. 4 (2018) 1850040 (8 pages)
°
cWorld Scienti¯c Publishing Company
DOI: 10.1142/S0218625X18500403
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1850040-1

of residual stress,
7
fracture toughness
8,9
as well as
adhesion of coating to substrate.
10–12
Therefore,
hardness and elastic modulus are extremely impor-
tant parameters for wear-resistant coatings, espe-
cially for wear resistance and durability.
Powder Immersion Reaction-Assisted Coating
(PIRAC) method is a solid state pack cementation
method with advantageous to coat complex-shape
components.
13–15
Three-point bend testing and in hip
simulation tests against ultrahigh molecular weight
(UHMW) polyethylene have demonstrated that
PIRAC method can provide good interfacial adhesion
and a low residual stress.
16,17
However, there are no
studies reported on hardness and elastic modulus of
titanium nitride coatings prepared by PIRAC.
In the present paper, hardness and elastic modulus
of titanium nitride coatings prepared by PIRAC are
tested and comparatively studied with a PVD TiN
coating. The aim of the current contribution is to gain
primary knowledge of the hardness and elastic mod-
ulus of the PIRAC titanium nitride coatings.
2. Experimental Procedure
Bulk Ti6Al4V with a thickness of 1 mm is used as
substrate and the surface for coatings is ¯nally
polished with a 0.24 m diamond suspension. After
ultrasonic cleaning in ethanol and drying, PIRAC
method is applied to prepare titanium nitride coating.
Firstly, the polished and dried substrates were
transferred into a glove box under the protection of
high purity nitrogen gas. Then the substrates were
immersed in Cr
2
N powder and sealed in containers
made of a 26 wt.% Cr stainless steel container. The
pre-sealed container is following sealed into an addi-
tional stainless steel container with small amounts of
titanium and chromium powder acting as getters for
N
2
and O
2
, respectively. Thus, very low partial
pressures not exceeding 105Pa of N
2
and O
2
were
maintained in the inner container during annealing.
12
Then some of the sealed substrates were treated at
750C for 24 h, some were treated at 800 Cfor8h,
respectively. The details of PIRAC are described
elsewhere.
16
For comparison, multilayered TiN coat-
ings are prepared by electron beam plasma-assisted
physical vapor deposition (EBPA-PVD). The multi-
layered EBPA-PVD TiN coatings are produced at
two di®erent thicknesses (6 m and 12 m), by
varying the number of coating cycles from 2 cycles to
4 cycles, respectively. Each TiN layer cycle had a 0.1–
0.2 m titanium interlayer and a total coating
thickness of approximately 3 m. For all coating
cycles, bulk temperature of the substrates is moni-
tored using a thermocouple; the coating temperature
did not exceed 500C.
Two approaches are employed to determine
thickness of the PIRAC nitride layers. The ¯rst one is
using nitrogen pro¯les determined by energy disper-
sive spectrometry (EDS) to estimate the thickness of
the nitride layer. The EDS is points line scan in which
the distance and number of points can be de¯ned,
rather than quantifying pixel-by-pixel. For every
prepared coating, three samples are tested and at
least two points line scan are conducted for each
sample. Average value is adopted. In the second ap-
proach, the thickness of nitride layer is measured by
scanning electron microscopy (SEM). The polished
cross-section of the coated samples is ¯rstly etched in
a diluted nitrohydrochloric acid (with 100 volumes of
deionized water, 3 volumes of 40% HF and 5 volumes
of 65% HNO
3
) for 5 min. Then samples are cleaned
and observed with SEM. Average of the measured
thickness by the two approaches is used as the coat-
ings thickness.
Phase composition and microstructure of the
coating are characterized using X-ray di®raction
(XRD, X'Pert Pro, Philips, Netherlands) and scan-
ning electron microscopy (SEM, S-3400N) equipped
with EDS. XRD analysis is operated at 40 KV
and 40 mA. Step scans are taken in the range of
2¼30–75with a 0.02step, 0.01/s scan speed and
a 2 s exposure.
Three-point bend tests are performed to assess the
elastic modulus of the coatings. The three-point
bending tests are performed on SANS CMT4304
universal testing machine (made by Shenzhen SANS
testing Machine Co. Ltd., Shenzhen Guang Dong,
China). The span is 16 mm and loading rate is
0.05 mmmin1. The elastic modulus of the coatings is
calculated according to
18
EsIsþXEcIc¼EI ¼PS 3
48d;ð1Þ
where Iis inertia moment, Pand dis the load and
corresponding displacement in the elastic scope dur-
ing the bending test. Sis the span, Eis the elastic
modulus. The subscript cand srepresent the coating
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1850040-2

and the substrate, respectively. Inertia moment of the
substrate and the coating can be calculated by
Is¼bh3
12 ;
Ic¼b
24 ½h3ðh2tÞ3;
where his the height of the coated sample, tis the
thickness of the coating, bis the width of the sample.
The elastic property of Ti6Al4V used in the calcula-
tions is Es¼113:8 GPa.
19
Microhardness test is conducted employing
Huaying testing machine (HV1000) under load 25 g
with Vickers and Knoop diamond indenter for planar
coated surface and cross-sections, respectively. Three
samples are tested for each coating treatment. A total
of nine indentation points are collected for each
sample.
3. Results and Discussion
Figure 1 shows XRD patterns of the coated samples.
It can be con¯rmed that PIRAC produced titanium
nitride is TiN and Ti
2
N, in which Ti
2
N is the main
phase. Phase composition of those samples coated by
PVD di®ers from those of PIRAC. The TiN with a
preferred orientation of (111) is the main phase for
the PVD coating, accompanied by a spot of Ti
2
N.
Figure 2 shows typical atomic concentration pro-
¯les across the nitriding di®usion zone of the polished
cross-section of the coated samples obtained using
EDS by points line scan. From Fig. 2, it can be seen
that atomic percent of nitrogen of PIRAC coatings
gradually decreases with the distance increasing. This
result indicated that the gained nitride layer has
multi-components, i.e. TiN, Ti
2
N and Ti(N) solid
solutions as detected by XRD and the thickness of the
TiN is very thin. The results are similar to that of Ti
alloys PIRAC treated at 900C in which the formed
nitriding layer was checked by XRD and quantitative
electron probe X-ray microanalysis (EPMA). Similar
results are also observed in high temperature nitrid-
ing of titanium by nitrogen,
20,21
ion implantation
method
22
and other methods.
23
While that of PVD
TiN coatings show a stable nitrogen zone with atomic
ratio of N to Ti of 1:1 corresponding to TiN, then
nitrogen content steeply decreased at the interface of
PVD TiN/Ti6Al4V substrate. Moreover, it can be
concluded that the thickness of the nitride layer of
samples after PIRAC treated at 750C for 24 h and
that at 800C for 8 h is about 3.7 m and 4.3 m,
respectively. While the thickness of nitride layer of
the 6 m PVD TiN coating is about 6.2 m. From the
EDS results, it also can be seen that the distance/
depth at which Al signal starts to increase is not the
same as the depth where Nsignal drops to 0.
The PIRAC is a di®usion controlled process and
the growth rate of hard TiN-based coatings on Ti
alloys is hampered by low rate of di®usion of nitrogen
in TiN compared to di®usion of nitrogen in Ti
alloys.
24,25
Therefore, it is hypothesized that di®usion
of nitrogen through Ti
2
N limits the growth of Ti
2
N
and Ti di®uses more readily to the initially formed
TiN/Ti interface and reacts further with TiN to form
TiN1x(such as Ti
2
N) and a similar reason leads to
the formation of Ti(N) solid solution. On the other
hand, the di®usion coe±cient of N in the titanium
nitride is orders of magnitude smaller than that in the
Ti(N) solid solution,
26,27
the thickness of Ti(N) solid
solution is thicker. While the di®usion coe±cient of
Al in the titanium nitride is orders of magni-
tude smaller than that of N,
28
suggesting the outward
di®usion of Al is smaller than the inward di®usion of
N. Therefore, the distance/depth at which Al signal
starts to increase is not the same as the depth where
N signal drops to 0.
Figure 3 shows cross-section image of the 12 m
PVD TiN coating and the etched cross-section back
scanning electron (BSE) image of samples after
PIRAC treatments. It can be seen that the thickness
of the PVD TiN is about 12.3 m, while the average
thickness measured from the etched sample of the
Fig. 1. Several surface XRD patterns of the coated
samples.
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1850040-3

coating prepared by PIRAC treated at 750C for 24 h
and that at 800C for 8 h is about 3.4 and 4.5 m,
respectively. Both the PVD and PIRAC titanium
nitride layers are homogeneous in thickness. Howev-
er, it can be found that there are small °uctuations in
the thickness of Ti(N) solid solution layer. The
thickness of both Ti(N) solid solution and titanium
nitride layers of samples after PIRAC treated at
800C for 8 h is thicker. Compared with the thickness
obtained from the nitrogen pro¯le shown in Fig. 2,
the measured thickness is very close.
Results of microhardness with Vickers indenta-
tions of the coated surface are presented in Fig. 4. It
can be seen that the surface hardness of the samples
of PVD coating is about 22 GPa close to that of
reported.
29
While the surface hardness of PIRAC
coating is about 10.98 GPa when treated at 750 C for
24 h and 11.32 GPa when treated at 800C for 8 h. It
should be noted that the deviation of surface hardness
for PIRAC coating (2.07 to 1.02 GPa when treated
at 750C for 24 h and 2.50 GPa to 1.21 GPa when
treated at 800C for 8 h) is larger than that for PVD
coating (1.27 GPa to 1.19 GPa for 6 m PVD TiN
and 0.83 GPa to 0.75 GPa for 12 m PVD TiN).
Under the indentation load of 25 g, the calculated
corresponding indent depth is about 0.91 0.06 m
for PIRAC coating. This indent depth is much less
than the thickness of the whole nitride coating while
close to the total thickness of the TiN and Ti
2
N lay-
ers. Therefore, deformation of the substrate can be
ignored. As mentioned above, the PIRAC titanium
nitride coatings have a gradually decreasing nitrogen
pro¯les corresponding to TiN, Ti
2
N, Ti(N) solid so-
lution. The TiN and Ti
2
N layers are very thin com-
pared to the Ti(N) solid solution layer. Moreover,
thickness of each layer and the whole coating varies
with PIRAC treatment as shown in Fig. 2. For mul-
tilayer coatings, the tested hardness should be the
composite layers' hardness and depends on hardness
and thickness of each layers. The hardness of Ti(N)
solid solution is about 10 GPa,
20,29
while hardness of
the TiN and Ti
2
N is much higher. According to the
rule of mixture, hardness of composite, Hccan be
described as
30–32
Hc¼HhfhþHsfs;ð2Þ
where Hc,Hhand Hsare the hardness values of the
composite, hard and soft phases, respectively. fh,fs
Fig. 2. Typical concentration pro¯les across the nitriding di®usion zone of the polished coated samples obtained using EDS
by points line scan.
Note: Distance of the start point to surface is about 0.5 m.
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1850040-4

are the volume fractions of hard and soft phases,
respectively. Moreover, as mentioned above, a total of
nine indentation points are collected for each sample
and three samples are tested for each coating treat-
ment. There are di®erences in every tested point
location and sample, and therefore there is variability
in Npro¯le. As a result, the surface hardness of
PIRAC coating should be much lower than hardness
of TiN while slightly higher than that of Ti(N) solid
solution and it showed large °uctuations as shown in
Fig. 4. For PVD coating, the calculated correspond-
ing indent depth is about 0.64 0.03 m, which is
much less than the thickness of the whole nitride
coating. Therefore, the tested hardness re°ects that of
the TiN layer. High temperature corresponds to high
di®usion and high reaction rate. The formed nitriding
layer for the 800C 8 h PIRAC-treated samples is
thicker than that for the 750C 24 h PIRAC-treated
samples, while the treatment time is shorter for the
former. Therefore, the Ti pro¯le is more variable for
800C 8 h PIRAC-treated samples when compared to
750C 24 h PIRAC-treated samples as it has thicker
titanium nitride layer and higher nitrogen content.
Moreover, the thickness of Ti(N) solid solution layer
is varies for 800C 8 h PIRAC-treated samples as
shown in Figs. 3(b) and 3(c). As a result, surface
hardness of PIRAC coating for those treated at
800C for 8 h is slightly higher, the same for vari-
ability in hardness. On the other hand, it has been
revealed that the hardness of titanium nitriding layer
signi¯cantly increases with N content increasing
when N content is below 30 at.%. While it is almost a
constant hardness value of approximately 20 GPa
within the range of 45 and 55 at.% N including stoi-
chiometric TiN.
29
In addition, the TiN and Ti
2
N
(a)
(b)
(c)
Fig. 3. Cross-section image of (a) the 12 m PVD TiN
coating and the etched cross-section back scanning electron
(BSE) image of samples (b) after PIRAC treated at 750 C
for 24 h; (c) the etched cross-section BSE image of after
PIRAC treated at 800C for 8 h.
Fig. 4. Surface microhardness of the coated samples.
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layers are thin for the PIRAC coating. Therefore, the
deviation of surface hardness for PIRAC coating is
larger than that for PVD coating.
Figure 5 shows Knoop microhardness pro¯les
measured across the cross-section of the coated sam-
ples. It can be seen that the PVD-coated samples
have a steep decreased hardness distribution pro¯le
from 22 GPa of the PVD TiN coating to 4.5 GPa
of Ti6Al4V substrate. While PIRAC-coated sample
showed a gradually decreasing hardness pro¯le from
surface to substrate, which corresponded with atomic
concentration pro¯les across the nitriding di®usion
zone of the coated samples. It is considered that this
decreased hardness pro¯le from surface to substrate is
bene¯cial to fracture toughness and adhesion of the
coating.
33–35
Figure 6 shows the results of calculated elastic
modulus of the coatings according to Eq. (1). The
results show that the elastic modulus of the PVD
coating is about 426 GPa, close to that reported by
others
36
and independent on coating thickness. The
elastic modulus of the PIRAC coating prepared at
750C for 24 h and at 800C for 8 h is about 234 and
293 GPa, respectively. Moreover, similar to surface
hardness, the deviation of elastic modulus for PIRAC
coating (15.53 GPa to 9.69 GPa for treated at 750C
for 24 h and 6.25 GPa to 4.22 GPa for treated at
800C for 8 h) is larger than that for PVD coating
(3.81 GPa to 4.76 GPa for 6 m PVD TiN and
3.75 GPa to 3.32 GPa for 12 m PVD TiN) indi-
cating that the coating composition has in°uence on
elastic modulus. It has been pointed out that smaller
elastic modulus mismatch is favorable to reduce
residual thermal stress, but improves toughness and
interface adhesion of coatings.
37
From this result, it
can be concluded that the elastic modulus of the
PIRAC coatings can be adjusted by changing of the
preparing parameters (i.e. temperature and treatment
times) and thus improve the coatings properties.
The in-plane elastic modulus of laminates Eeff can
be described by the rule of mixture:
Eeff ¼XEiVi;ð3Þ
where E;Vare the Young's modulus and the volume
fractions, respectively. The subscripts cand srepre-
sent the coating and the substrate, respectively. The
relationship of elastic modulus and hardness of tita-
nium nitride to nitrogen content is similar.
29
The
elastic modulus of titanium nitriding layer signi¯-
cantly increases with increasing N content when N
content is below 20 at.%; while it is almost a constant
elastic modulus value of approximately 400 GPa
within the range of 20–30 at.% N, and approximately
400 GPa within the range of 30–30 at.% N. In addi-
tion, the TiN and Ti
2
N layers are very thin for the
PIRAC coating. Therefore, the deviation of surface
hardness for PIRAC coating is larger than that for
PVD coating. Therefore, elastic modulus of Ti
2
Nis
the highest, while that of Ti(N) solid solution is the
lowest. As a result, elastic modulus of the PIRAC
coating is smaller than that of the PVD coating.
Moreover, thickness of each layer and the whole
coating varies with PIRAC treatment which leads to
the deviation of elastic value for PIRAC coating
being larger than that for PVD coating.
Based on the above results and discussion, it can
be summarized that nitrogen di®usion hardening of
Fig. 6. Elastic modulus of the coatings.
Fig. 5. Knoop microhardness of the coated samples as a
function of the distance from the surface.
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the substrate beneath the TiN PIRAC layer can de-
crease interfacial discontinuities in hardness and thus
provide superior load-bearing capacity and coating/
substrate adhesion. PIRAC nitriding produced coat-
ing showed low level of residual stresses, improved
fracture toughness, adjustable properties. However,
the PIRAC is a limited di®usion controlled process
and very long processing time is needed for growing a
thick layer. PVD and other methods, such as chemi-
cal vapor deposition (CVD), laser cladding have
advantages to prepare uniform and thicker coating.
However, because of abrupt mismatch in composition
and properties between the coating and substrate,
coatings prepared by such PVD and CVD methods
carry a potential of adhesive failure. Preliminary
work con¯rmed that the combination of PIRAC
and PVD can enhance advantages and minimize
disadvantages.
38
4. Conclusions
PIRAC coatings show gradually decreased nitrogen
pro¯les from surface to substrate corresponding to
TiN, Ti
2
N and Ti(N) solid solution.
Surface hardness of the PIRAC coatings is about
11 GPa, much lower than that of PVD coating of
22 GPa. The hardness distribution pro¯le from surface
to substrate of the PVD coatings is steeply decreased
from 22 GPa to 4.5 GPa of Ti6Al4V substrate
while that of the PIRAC coatings is gradual decreased.
Elastic modulus of the PVD coating is about
426 GPa, while that of the PIRAC coatings is
adjustable. Elastic modulus of the PIRAC coating
prepared at 750C for 24 h and at 800 C for 8 h is
about 234 and 293 GPa, respectively.
Acknowledgments
The authors gratefully acknowledge the ¯nancial
support from the fund of the State Key Laboratory of
Solidi¯cation Processing in NWPU (SKLSP201304)
and the fund of the Creative Research Foundation of
Science and Technology on Thermostructural Com-
posite Materials Laboratory (6142911020105).
References
1. M. Geetha, A. K. Singh, R. Asokamani and A. K.
Gogia, Prog. Mater. Sci. 54 (2009) 397.
2. I. M. Pohrelyuk, V. M. Fedirko, O. V. Tkachuk and
R. V. Proskurnyak, Corros. Sci. 66 (2013) 392.
3. V. H. Pham, S. H. Jun, H. E. Kim and Y. H. Koh,
Appl. Surf. Sci. 258 (2012) 2864.
4. Ł.Łapaj, J. Wendland, J. Markuszewski, A. Mróz and
T. Wiśniewski, J. Mech. Behav. Biomed. Mater. 55
(2016) 127.
5. M. Olsson, L. Kahlman and B. Nyberg, Am. Ceram.
Soc. Bull. 74 (1995) 48.
6. R. M
ascia, F. F. Ramos Neto, T. F. Barbosa Neto and
S. D. Franco, Wear 303 (2013) 412.
7. X. C. Zhang, M. Watanabe and S. J. Kuroda, Engin.
Fract. Mech. 110 (2013) 314.
8. J. J. Chen, Phys. D: Appl. Phys. 45 (2012) 1.
9. W. G. Mao, J. Wan, C. Y. Dai, J. Ding, Y. Zhang, Y. C.
Zhou and C. Lu, Surf. Coat. Technol. 206 (2012) 4455.
10. K. S. Lee, J. Mech. Sci. Technol. 17 (2003) 1928.
11. T. G. Wang, Y. M. Liu, Q. M. Wang, J. Gong, C. Sun
and K. H. Kim, Curr. Appl. Phys. 12 (2012) S59.
12. O. P. Oladijo, A. M. Venter and L. A. Cornish, Int. J.
Refract. Met. Hard Mater. 44 (2014) 68.
13. L. Vandenbulcke, G. Leprince and B. Nciri, Mater. Sci.
Eng. A. 120 (1989) 379.
14. R. P. van Hove, I. N. Sierevelt, B. J. van Royen and
P. A. Nolte, BioMed. Res. Inter. 2015 (2015) 485975.
15. I. Gotman and E. Y. Gutmanas, Adv. Biomater.
Device in Med. 1(2014) 53.
16. A. Shenhar, I. Gotman, E. Y. Gutmanas and
P. Ducheyne, Mater. Sci. Eng. A 268 (1999) 40.
17. A. Shenhar, I. Gotman, S. Radin, P. Ducheyne and
E. Y. Gutmanas, Surf. Coat. Technol. 126 (2000) 210.
18. N. Fawcett, Meas. Sci. Technol. 9(1998) 2023.
19. Z. Anjum, F. Qayyum, S. Khushnood, S. Ahmed and
M. Shah, Mater. Des. 87 (2015) 750.
20. J.-P. Bars, D. David, E. Etchessahar and J. Debuigne.
Metall. Trans. 14 (1983) 1537.
21. K. N. Stratford and J. M. Towell, Oxid. Metal. 10
(1976) 41.
22. K. Volz, W. Ensinger, B. Stritzker and B. Rauschen-
bach, Surf. Coat. Technol. 103–104 (1998) 257.
23. T. Hayashi, A. Matsumuro, M. Muramatsu, Y. Taka-
hashi and K. Yamaguchi, Thin Solid Films 349 (1999)
199.
24. F. Abautret and P. Eveno, Revue phys. Appl. 25
(1990) 1113.
25. A. D. LeClaire ed. H. Mehrer SpringerMaterials —The
Landolt-B€
ornstein Database, P. 486, http://www.
springermaterials.com. doi: 10.1007/10390457 90.
26. V. Fouquet, L. Pichon, A. Straboni and M. Drouet,
Surf. Coat. Technol. 186 (2004) 34.
27. E. Metin and O. T. Inal, Metall. Trans. A 20 (1989)
1819.
28. G. I. Grigorov, K. G. Grigorov, M. Stoyanova, J. L.
Vignes, J. P. Langeron and P. Denjean, Appl. Phys. A
57 (1993) 195.
29. F. Vaz, J. Ferreira, E. Ribeiro, L. Rebouta, S. Lanceros-
M
endez, J. A. Mendes, E. Alves, Ph. Goudeau,
Hardness and Elastic Modulus of Titanium Nitride Coatings
June 9, 2017 7:24:23am WSPC/149-SRL 1850040 ISSN: 0218-625X
P
age
P
roo
f
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
1850040-7

J. P. Rivière, F. Ribeiro, I. Moutinho, K. Pischow and J.
de Rijk, Surf. Coat. Technol. 191 (2005) 317.
30. S. Chatterjee, T. S. Udarshan and S. Chandrashekhar,
J. Mater. Sci. 28 (1992) 1989.
31. H. S. Kim, Mater. Sci. Eng. A. 289 (2000) 30.
32. A. E. Santana, A. Karimi, V. H. Der°inger and
A. Schützeb, Surf. Coat. Technol. 177–178 (2004) 334.
33. W. Lengauer and K. Dreyer, Int. J. Refract. Met. Hard
Mater. 24 (2006) 155.
34. S. Takago, H. Yasui, A. Uemura, T. Inoue and
K. Sakurai, Jpn. J. Appl. Phys. 53 (2014) 05FH08.
35. Z. Y. Zeng, H. Q. Xiao, X. H. Jie and Y. M. Zhang,
Trans. Nonferrous Met. Soc. China 25 (2015) 3716.
36. A. S. Maxwell, S. Owen-Jones and N. M. Jennett, Rev.
Sci. Instrum. 75 (2004) 970.
37. T. W. Clyne and S. C. Gill, J. Therm. Spray. Technol.
5(1996) 401.
38. J. C. Avelar-Batista Wilson, S. J. Wu, I. Gotman,
J. Housden and E. Y. Gutmanas, Mater. Lett. 157
(2015) 45.
S. Wu et al.
June 9, 2017 7:24:23am WSPC/149-SRL 1850040 ISSN: 0218-625X
P
age
P
roo
f
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29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
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47
48
49
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