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Influence of Al content on microstructure, mechanical and tribological properties of Ti-W-Al-N composite films
Accepted Manuscript Influence of Al content on microstructure, mechanical and tribological properties of TiW-Al-N composite films Lihua Yu, Jian Chen, Hongbo Ju, Hongzhi Dong, Hongjian Zhao PII:
S0042-207X(16)30810-7
DOI:
10.1016/j.vacuum.2016.11.004
Reference:
VAC 7186
To appear in:
Vacuum
Received Date: 11 March 2016 Revised Date:
2 November 2016
Accepted Date: 4 November 2016
Please cite this article as: Yu L, Chen J, Ju H, Dong H, Zhao H, Influence of Al content on microstructure, mechanical and tribological properties of Ti-W-Al-N composite films, Vacuum (2017), doi: 10.1016/j.vacuum.2016.11.004. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Influence of Al content on microstructure, mechanical and tribological properties of Ti-W-Al-N composite films Lihua Yu*, Jian Chen, Hongbo Ju, Hongzhi Dong, Hongjian Zhao
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School of Materials Science and Engineering, Jiangsu University of Science and Technology, Mengxi Road 2, Zhenjiang, Jiangsu Province, 212003, China
Abstract: Ti-W-Al-N films with various Al content (0 at.% ~ 12.4 at.%) were deposited by
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reactive magnetron sputtering. The composition, microstructure, mechanical and tribological properties of Ti-W-Al-N films were investigated by EDS, XRD, HRTEM, SEM,
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Nano-indentation, Ball-on-disk tribometer. It is found that Ti-W-Al-N films consist of Ti-W-Al-N phase, Ti2N phase and W2N phase below 2.9 at.% Al. Ti2N phase disappears at 5.6 at.% Al and h-AlN phase forms at 12.4 at.% Al respectively. The hardness firstly increases and then decreases with increasing Al content and the highest hardness is 35.7 GPa at 8.7 at.% Al. At room temperature, the friction coefficient continuously increases,
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whereas the wear rate firstly decreases and then increases with increasing Al content. The lowest wear rate of 1.79×10-8 mm3N-1mm-1 is obtained at 8.7 at.% Al. As the temperature increases from room temperature to 700
, the friction coefficient firstly increases and then
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decreases, while the wear rate gradually increases. The tribological properties of the film depended on the testing temperatures significantly because the testing temperatures
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influenced the hardness, the tribo-films and wear mechanism of the film. Keywords: reactive magnetron sputtering; microstructure; mechanical property; tribological property
1. Introduction
Over the past decade, the development of nanostructured composite films has resulted in considerable improvement in comparison to single hard films (TiN, ZrN, CrN, etc) in terms of their outstanding performance[1-3]. Recently, TiWN films have been widely 1
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applied to resistance transmitters and cutting tools because of their high hardness, excellent corrosion resistance, good adhesion[4-6]. We have previously reported that TiWN composite films revealed a high hardness of 30.7 GPa and had the ability to adapt self
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lubrication due to forming Magnéli phase oxide WO3, which could obviously reduce the friction coefficient and effectively improve tribological properties[7]. However, relative high wear rate and poor oxidation resistance limited performance of TiWN films at high
SC
temperature[8-10]. Studies[11-14] on Ti-Al-N system showed that Al added to the films can effectively improve the oxidation resistance due to the density Al2O3 oxide layer forming on
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the surface of the films. Although the high Al content films showed excellent oxidation resistance, the hardness decreased in terms of h-AlN phase (the hardness value ≤26GPa) forming in the films[15-16].
In this study, Ti-W-Al-N composite films with various Al content were prepared by a reactive magnetron sputtering system to obtain excellent tribological properties and
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oxidation resistance. Previous study showed that Ti-W-Al-N films have better corrosion behavior[17]. However, the tribological performance of Ti-W-Al-N films is seldom studied in detail. The microstructure, mechanical and tribological performance at room/high
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temperature of Ti-W-Al-N films were investigated. In addition, the wear mechanism at high temperature were discussed.
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2. Material and methods In this study, Ti-W-Al-N films with a thickness of about 2 µm were deposited on both
single crystal silicon (100) wafers and polished 304 stainless steel coupons (15 mm×15 mm×2.5 mm) substrates using JGP-450 type reactive magnetron sputtering system. Ti target (99.9 %), W target (99.9 %) and Al target (99.9 %) with a diameter of 75 mm were sputtered by three radio frequency powers. Silicon wafers and polished stainless steel substrates were ultrasonically cleaned in acetone and alcohol for 10 min, respectively. The substrates were 2
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mounted on a substrate holder and installed at a distance of 78 mm from the target. A base pressure of less than 6.0×10-4 Pa was reached prior to all film depositions. The substrates were RF sputter-etched by Ar plasma bombardment at a target power of 40 W to remove the
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surface contaminants. Prior to the Ti-W-Al-N films deposition, a thin Ti adhesion layer, with a thickness of 100 nm, was first deposited by sputtering from Ti target using target power of 150 W. Subsequently, Ti-W-Al-N films were deposited in Ar and N2 mixtures with the gas
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flow of 10 sccm and 2 sccm. During film depositions, Ti and W target power of 250 W and 90 W was fixed and Al target power was fixed for 0, 25, 50, 75 and 100W, respectively. The
bias was used for all depositions.
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working pressure was maintained constant at 0.3 Pa. Neither substrate heating nor substrate
The chemical composition of Ti-W-Al-N films with various Al power targets was investigated by a field emission electron probe microanalyzer (FM-EPMA, JXA-8500F, JEOL, Japan). The microstructure of the films was characterized using Island Ferry X-ray
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6000 X-ray diffraction with monochromatic Cu Kα radiation at a grazing angle of 4° and high resolution transmission electron microscopy (HRTEM) operated at 200 kV. The average grain size of Ti-W-Al-N films was calculated by Scherrer formula (Eq.(1)) using the
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data of the diffraction peaks of TiN (111) and (200), which are belong to the face-centered
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cubic (fcc) TiN pahse.
D = Kγ / Bcosθ
(1)
where K is Scherrer constant (K=0.89), γ is the wavelength of X-ray (γ=0.154056 nm), B is the FWHM of XRD diffraction peak, θ is the diffraction angle. The lattice constant of the films was also calculated using the data of the diffraction peaks of TiN (111) and (200). Scanning electron microscope (SEM, JMS-6480) was used to observe worn surface morphologies of the films after wear tests at high temperature. The thickness was calculated by the cross-sectional SEM image. The hardness of the films were determined using nano 3
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indentation tester system (nano-indenter CPX + NHT + MST), which were equipped with a diamond Berkovich indenter tip (3-side pyramid). The hardness measurements were performed with the maximum applied load of 5 mN to meet the indentation depth less than
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10 % to reduce the effect of Si substrate on the values. 9 repeated indentations were made for each sample. The oxidation resistance of the film was measured using thermogravimetric analysis system (STD-2960,TA Instrument). Due to the inability of the film to be stripped
heated from 150
to 700
at a heating rate of 15
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from the substrate, the film and the silicon substrate were tested together. The sample was /min and 60 ml/min of air to maintain
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an oxidative atmosphere. Ball-on-disk wear tests were carried out to measure the tribological behavior of the films using UMT–2 tribometer with alumina ball counterpart (9.38 mm in diameter). The test counterpart was sliding in a circular path with a radius of 4 mm at a relative velocity of 50 r/min. Each sample was tested for 30 min. The wear rates of the films were measured using Dektak surface profilometer by taking average measurements
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along the wear track. The wear rate (Ws) of the films was calculated by Eq.(2). Ws = C × S /( F × L)
(2)
where Ws is wear rate; S is wear track area; C is perimeter of wear crack; F is the normal
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load; L is sliding length. The residual stresses were calculated by Stoney’s equation (Eq(3))
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using Dektak surface profilometer. σ = Es t s2 (1 / R − 1 / R0 ) /[6(1 − υ s )t f ]
(3)
Where Es is the elastic modulus of the substrate (Es=170 GPa), υs is the Poisson’s ratio of the substrate (υs=0.3), ts is the thickness of the substrate, tf is the thickness of film, R is the curvature of film, R0 is the curvature of Si substrate.
3. Results and discussion 3.1 Chemical composite and microstructure
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The chemical compositions of the Ti-W-Al-N films are summarized in Table1. As the Al target power increases from 0 to 100W, the Al content increases linearly from 0 to 12.4 at.%. With the increase of Al content, the lattice constant of TiN phase and grain size of TiN
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phase gradually decrease. This suggests that Ti and W atoms are replaced gradually by the Al atoms forming the substitutional solid solution. The decrease in the grain size suggests that the incorporation of Al could result in the re-nucleate.
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Fig.1(a) shows the XRD patterns of Ti-W-Al-N films with different Al content. It can be seen that fcc-TiN phase, Ti2N phase and W2N phase coexist in the Ti-W-Al-N films when
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the Al content is in the range of 0 at.%-2.9 at.%. When the Al content at 5.6 at.%, Ti2N phase disappeared and the films consisted of fcc-TiN phase and W2N phase. With a further increase in the Al content, h-AlN phase appeared and the films consisted of fcc-TiN phase, h-AlN phase and W2N phase as shown in Fig.1(b)[17]. Further details of the microstructure of Ti-W-Al-N film with 12.4 at.% Al are revealed by HRTEM image as shown in Fig.2.
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Three sets of lattice fringes with a lattice spacing of about 0.235 nm, 0.210 nm and 0.144 nm are observed, which are corresponding to the h-AlN (101), c-TiN (200) and c-W2N (220) respectively.
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The lattice constant and grain size (calculated by Eq(1)) of Ti-W-Al-N films with various Al content are listed in Table 1. The lattice constant and grain size of TiWN film are
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about 0.423 nm and 28.7 nm, respectively. As the increase of Al content, the lattice constant and grain size of Ti-W-Al-N films gradually decrease. When the Al content is less than 8.7 at.%, the lattice constant contracts with the substitution of Ti and W atoms by the smaller size Al atoms in the solid solution. Excessive Al atoms react with nitrogen atoms forming h-AlN phase as the Al content increases to 12.4 at.%. Consistent with the decreasing tendency of the lattice constant, the grain size decreases from 24.8 nm at 2.9 at.% to 11.7 nm at 12.4 at.%. 5
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3.2 Mechanical properties Fig.3 shows the hardness and residual stress of Ti-W-Al-N films with different Al content. It is found that the hardness of Ti-W-Al-N films increases from 30.7 GPa to 35.7
as the Al content further increases to 12.4 at.%.
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GPa as the Al content increases from 0 at.% to 8.7 at.%. The hardness decreases to 32.4 GPa
Many factors influence the hardness of the films. According to the reported studies, the
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hardness enhancement are mainly attributed to solid solution strengthening[18] and grain size refinement[19-20]. Besides, it is also imputed to the compress residual stress[21] in the
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films. In the Ti-W-Al-N films, Ti atoms and W atoms are replaced by Al atoms forming substitutional solid solution. As increase of the Al content, the grain size refines and there exhibits compress residual stress in the films. So the hardness enhancement of the films is mainly associated with solid solution strengthening, grain size refinement and the compress residual stress. As the Al content increases to 12.4 at.%, the hardness decreases due to the
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saturation of Al content weakening solid solubility strengthening and causing the compress stress relaxation. In addition, the appearance of the AlN phase in the film also leads to the decrease of the hardness of the film when the Al content is 12.4 at.% because the hardness
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of the binary AlN film deposited under the same condition is about 21 GPa.
3.3 Tribological properties
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Fig.4 shows the friction curves, the average friction coefficient and wear rate of the
Ti-W-Al-N films with different Al content at room temperature. It can be seen from Fig.4(a) that the friction slightly increases before 200 s, and then decreases and gradually stabilizes. With the increase of Al content, the friction coefficient of the films gradually increases, whereas the wear rate decreases first and then increases. The lowest wear rate of 1.79×10-8 mm3N-1mm-1 is obtained at 8.7 at.%, as shown in Fig.4(b). The tribo-film plays an important role in the tribological properties of the films and the 6
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phenomenon of tribo-oxidation can be observed in wear test at room temperature. Fig.5 shows the XRD patterns of the Ti-W-Al-N films with different Al content after wear test at room temperature. As the Al content is less than 10.39 at.%, WO3 is detected and the
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diffraction peaks of WO3 gradually weakens along with the increase of Al content. When the Al content is higher than 8.7 at.% , no WO3 is detected in the films.
In order to study the tribological properties of Ti-W-Al-N films at high temperature, the ball-on-disk wear test of the film with 8.7 at.% Al has been done at 200
, 500
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and 700
, 400
,and the average friction coefficient and wear rate at different temperatures are
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showed in Fig.6(a). In order to study the influence of the Al element on the tribological properties of Ti-W-Al-N film at elevated temperatures, the friction coefficient and wear rate of Ti-W-N film at elevated temperatures are also shown in Fig. 6(b). For Ti-W-Al-N film, the friction coefficient increases first and then decreases, and reaches a maximum value of . As the temperature sequentially increases to 500
0.68 at 400
, the friction coefficient
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sharply decreases to 0.46. With the temperature further increase to 700
, the friction
coefficient decreases to 0.39. However, the wear rate gradually increases as the temperature increases, and reaches a maximum value of 3.24×10-7 mm3N-1mm-1 at 700
. The
temperatures.
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combination of Al into Ti-W-N film could improve the tribological properties at elevated
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Fig.7 shows the XRD patterns of the Ti-W-Al-N film (8.7 at.% Al)after wear test at
200
,400
,500
and 700
. It is found that no oxide appears at 200
and 400
the oxide of TiO2, Al2O3 and WO3 appear as the temperature increases to 500
,while
, indicating
that the film starts to oxide. With a further increase of the temperature, the diffraction peaks of the oxide phase become stronger and more, indicating a further oxidation of the film. In order to further verify the oxidation resistance of the Ti-W-Al-N films, the thermogravimetric analysis of the Ti-W-Al-N film (8.7 at.% Al) has been done and the TG 7
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curve is presented in Fig.8. The previous study[22] indicates that Al atoms oxidize forming amorphous Al2O3 at lower temperature (below 500
). With increase of the temperature, the
crystalline Al2O3 forms. As shown in the Fig.8, the weight of the film slowly increases as , which indicates that the
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the temperature increases when the temperature below 430
amorphous Al2O3 forming in the film as a dense protective layer to inhibit the deeper oxidation in the film [22]. When the temperature increases to 430
, the weight of the
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Ti-W-Al-N film dramatically increases due to the formation of the crystalline Al2O3. Then oxygen can easily diffuse inward the films through the grain boundary of the crystalline
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Al2O3 accelerating the film oxidation accompanied with a further formation of TiO2, WO3 and Al2O3, causing the rapid increase of the weight [22].
The hardness of the Ti-W-Al-N film (8.7 at.% Al) as a function of the annealed temperature is shown in Fig.9. With increasing annealing temperature to 400
, a slight
decrease of the hardness can be observed. Since neither variation of the microstructure nor
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oxidation is observed as shown in Fig.7, the decrease of the hardness could be attributed to the compressive stress relaxation, which is induced by the heat [23]. As the temperature is above 500
, the hardness decreases. This is due to that Ti-W-Al-N film obviously oxidizes
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and forms a large number of lower hardness oxides, TiO2, Al2O3, and WO3, which leads to the obvious decrease of the hardness.
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According to the previous studies, WO3 can reduce the friction coefficient in terms of
its layered structure [10]. The decrease of WO3 as the increase of the Al content can be observed in Fig.7, which is mainly attributed to amorphous Al2O3 formed on the surface of the films as a protective layer to inhabit oxygen diffusing inward the films. Then, the self-lubricating performance is weakened due to the decrease of WO3, which leads to a gradual increase of the friction coefficient. The wear rate is closely related to the hardness and the phase structure as reported in many studies[6,24]. High hardness materials are 8
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difficult to be worn. On the contrary, the layered structure materials could be worn easily because of their low shear strength. In this study, the wear rate gradually decreases as increase of the Al content when Al content is low than 8.7 at.%, which is attributed to the
hardness sharply decreases, the wear rate of the film increases.
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increase of the hardness and the decrease of WO3. With a further increase of Al content, the
The friction coefficient of the Ti-W-Al-N film (8.7 at.% Al) gradually increases as the . This may be due to the decreases of
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temperature increases from room temperature to 400
moisture[25] and the decrease of the self-lubrication oxide WO3. As the temperature , the crystalline Al2O3 forms in the film as shown in Fig.7, which
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increase to 500
accelerates the oxidation of the film resulting in the increase of the WO3[8]. Therefore, the friction coefficient widely decreases. The wear rate slightly increases as the temperature , which is the enhancement in oxidation
increases from room temperature to 400
resistance due to the formation of amorphous Al2O3 and the slightly decrease of the hardness
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in this temperature range. When the temperature increases to 500
and 700
, the
crystalline Al2O3 forms and accelerates the oxidation of the film leading to the sharp decrease of the hardness as shown in Fig.9, therefore, the wear rate rapidly increases.
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Fig.10 shows the wear track morphology of the TiWN film and the Ti-W-Al-N film (8.7 at.% Al) at 400
, 500
and 700
. It can be found that the wear track of the
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Ti-W-Al-N film is shallower in depth and lower in roughness than TiWN film’s at 400
as
shown in Fig.10(a) and Fig.10(b). This wear mechanism is slight adhesion and moderate abrasion. As the temperature increases to 500
, the TiWN and Ti-W-Al-N films exhibit
deeper wear track and worn spalling phenomena occurred on the surface of the films as shown in Fig.10(c)and Fig.(d), which is mainly due to the film oxidation and the formation of the susceptibly worn oxides. Some oxides are attached with the counterpart and transfer with the grinding ball causing the peeling off. The wear mechanism is a mixture of heavy 9
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adhesion and tribo-oxidation. Compared with 400
and 500
, as the temperature is 700
,
the wear tracks of the TiWN and Ti-W-Al-N films obviously become wider, and deeper. Serious crack appeared on the surface of the wear tracks and the films have been almost
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worn away as shown in Fig.10(e) and Fig.10(f).The wear mechanism is tribo-oxidation at this temperature.
4. Conclusion
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The Ti-W-Al-N films with different Al content were deposited by reactive magnetron
sputtering and the effects of Al content on the microstructure, mechanical properties and
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tribological properties of Ti-W-Al-N films were studied. The main results could be concluded as follows:
1) Ti-W-Al-N films consist of TiN phase, Ti2N phase and W2N phase below 2.9 at.% Al. Ti2N phase disappears at 10.4 at.% Al and h-AlN phase forms at 12.4 at.% Al respectively.
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2) The Ti-W-Al-N film containing 8.7 at.% Al has the highest hardness of 35.7GPa. The hardness enhancement of the films is mainly associated with solid solution strengthening, grain size refinement and the compress residual stress.
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3) At room temperature, the wear rate decreases first and then increases, whereas the friction coefficient gradually increases with increasing Al content at room temperature. The
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lowest wear rate of 1.79×10-8 mm3N-1mm-1 is obtained at 8.7 at.% Al. 4) For the Ti-W-Al-N film with 8.7 at.% Al, high temperature wear tests show that as
the temperature increases from room temperature to 700
, the friction coefficient firstly
increases and then decreases, while the wear rate gradually increases. The tribological properties of the film depended on the testing temperatures significantly because the testing temperatures influenced the hardness, the tribo-films and wear mechanism of the film.
Acknowledgments 10
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Supported by the National Natural Science Foundation of China (51374115, 51574131) and combined study of Industry University Research of Jiangsu Province (BY2013066-11).
References
produced by magnetron sputtering, Thin Solid Films 317 (1998) 351-355.
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[1] L. Cunha, M. Andritschky, L. Robouta, et al., Corrosion of TiN, (Ti,Al)N and CrN hard coatings
[2] Hongbo Ju, Junhua Xu, Microstructure, oxidation resistance, mechanical and tribological properties
SC
of Ti-Y-N films by reactive magnetron sputtering, Surface and Coatings Technology 283 (2015) 311-317. [3] J.H. Hsieh, T.H. Yeh, C. Li, et al., Antibacterial properties of TaN-(Ag,Cu) nanocomposite thin films, Vacuum 87 (2013) 160-163.
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[4] S. Zhou, W. Liu, H. Liu, et al., Structural and electrical properties of Ti-WN thin films deposited by reactive RF sputtering, Physics Procedia 18 (2011) 66-72.
[5] J.C. Caicedo, L. Yate, J. Montes, Improving the physicochemical surface properties on AISI D3 steel coated with TiWN, Surface and Coatings Technology 205 (2011) 2947-2953. [6] B. Tian, W. Yue, Z. Fu, et al., Microstructure and tribological properties of W-implanted PVD TiN
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coatings on 316L stainless steel, Vacuum 99 (2014) 68-75.
[7] Lihua Yu, Hongzhi Dong, Junhua Xu, Effect of W content on microstructure, mechanical and tribological properties of Ti1−xWxN composite films, Materials Science and Engineering of Powder Metallurgy 19 (2014) 812-817.
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[8] G. Gassner, P.H. Mayrhofer, K. Kutschej, et al., Magnéli phase formation of PVD Mo–N and W–N coatings, Surface and Coatings Technology 201 (2006) 3335-3341.
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[9] G.S. Fox-Rabinovich, K. Yamamoto, S.C. Veldhuis, et al., Self-adaptive wear behavior of nano-multilayered TiAlCrN/WN coatings under severe machining conditions, Surface and Coatings Technology 201 (2006) 1852-1860. [10] T. Aizawa, A. Mitsuo, S. Yamamoto, et al., Self-lubrication mechanism via the in situ formed lubricious oxide tribofilm, Wear 259 (2005) 708-718. [11] D. McIntyre, J.E. Greene, G. Hakansson, et al., Oxidation of metastable single-phase polycrystalline Ti0.5Al0.5N films: Kinetics and mechanisms, Journal of Applied Physics 67 (1990) 1542-1553. [12] K. Chakrabarti, J.J. Jeong, S.K. Hwang, et al., Effects of nitrogen flow rates on the growth 11
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morphology of TiAlN films prepared by an rf-reactive sputtering technique, Thin Solid Films 406 (2002) 159-163. [13] K. Kutschej, P.H. Mayrhofer, M. Kathrein, et al., Structure, mechanical and tribological properties of
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sputtered Ti1–x AlxN coatings with 0.5≤x≤0.75, Surface and Coatings Technology 200 (2005) 2358-2365.
[14] Chunyan Yu, Shebin Wang, Xiaoding Yin, et al., Study on high-temperature oxidation resistance of CrAlN coatings, Rare Metal Materials and Engineering 38 (2009) 1015-1018.
SC
[15] M. Brizuela, A. Garcia-Luis, I. Braceras, et al., Magnetron sputtering of Cr(Al)N coatings: Mechanical and tribological study, Surface and Coatings Technology 200 (2005) 192-197.
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[16] Yunke Ge, Xiaobo Gu, Lihua Yu, et al., Investigation of Phase Structure and Properties of (Zr, Al)N Coatings, Development and Application of Materials 23 (2008) 21-25.
[17] Christopher M.A. Brett, Albano Cavaleiro, A comparison of the electrochemical behavior of W-M-N (M=Ni, Ti, Al) thin film coatings on high speed steel, Thin Solid Films 322 (1998) 263-273. [18] E. Ertuerk, O. Knotek, W. Burgmer, et al., Ti(C, N) coatings using the arc process, Surface and
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Coatings Technology 46 (1991) 39-46.
[19] T. Yamamoto, M. Kawate, H. Hasegawa, et al., Effects of nitrogen concentration on microstructures of WNx films synthesized by cathodic arc method, Surface and Coatings Technology 193 (2005) 372-374.
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[20] W.Y. Wu, C.H. Wu, B.H. Xiao, et al., Microstructure, mechanical and tribological properties of CrWN films deposited by DC magnetron sputtering, Vacuum 87 (2013) 209-212.
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[21] L. Zhang, H. Yang, X. Pang, et al., Microstructure, residual stress and fracture of sputtered TiN films, Surface and Coatings Technology 224 (2013) 120-125. [22] J. Lin, B. Mishra, J.J. Moore, et al., A study of the oxidation behavior of CrN and CrAlN thin films in air using DSC and TGA analyses, Surface and Coatings Technology 202 (2008) 3272-3283. [23] T. Polcar, A. Cavaleiro, Structure, mechanical properties and tribology of W–N and W–O coatings, International Journal of Refractory Metals and Hard Materials 28 (2010) 15-22. [24] X. Chen, Z. Wang, S. Ma, et al., Microstructure, mechanical and tribological properties of Ti–B–C–N films prepared by reactive magnetron sputtering, Diamond and Related Materials 19 (2010)
12
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1336-1340. [25] G. Cheng, D. Han, C. Liang, et al., Influence of residual stress on mechanical properties of TiAlN
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SC
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thin films, Surface and Coatings Technology 228 (2013) S328-S330.
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Figure captions Fig.1 XRD patterns of TiWAlN films with different Al content Fig.2 HRTEM image of TiWAlN film with 12.4 at.% Al
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Fig.3 Hardness and residual stress of TiWAlN films with different Al content
Fig.4 The friction curves (a) and friction coefficient and wear rates (b) of TiWAlN films at room temperature
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Fig.5 XRD patterns of TiWAlN films after wear test at room temperature
Fig.6 Friction coefficient and wear rate of TiWAlN film at different temperatures(a)
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TiWAlN film at 8.7 at.% Al; (b) TiWAlN film at 0 at.% Al
Fig.7 XRD patterns of TiWAlN films after wear test at different temperatures Fig.8 TG curve of TiWAlN film with 8.7 at.% Al
Fig.9 Hardness of TiWAlN films (8.7 at.% Al ) as a function of annealed temperature Fig.10 Wear tracks morphology of TiWN films and TiWAlN films at high temperature (a), 500
(c) and 700
(e); wear tracks
morphology of TiWAlN composite films at 400
(b), 500
(d) and 700
(f))
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(wear tracks morphology of TiWN films at 400
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Fig.1
Fig.2
1
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Fig.4
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Fig.3
Fig.5
2
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Fig.6
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Fig.7
3
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Fig.9
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Fig.8
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Fig.10
4
(b)
(c)
(d)
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(a)
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(f)
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(e)
5
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1. TiWAlN films exhibit various microstructures depending on different Al content. 2. The film with 15.9 at.% Al has the highest hardness and the lowest wear rate at
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25℃.
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3. The TiWAlN films with Al have higher oxidation resistance temperature.
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Table caption Table 1 Chemical composition, lattice constant and average grain size of Ti-W-Al-N films Table 1 Chemical composition (at.% )
Al target (W)
Ti
W
Al
N
O
Lattice
Average
constant
grain
(nm)
Size
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Power of
37.7
20.5
0
39.4
2.4
0.4230
28.7
25
32.5
18.5
2.9
43.2
2.9
0.4218
24.8
50
30.8
17.3
5.6
43.8
2.5
0.4214
19.2
75
26.4
15.5
100
23.9
11.9
SC
0
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（nm）
46.7
2.7
0.4200
12.3
12.4
48.1
3.7
0.4199
11.7
AC C
EP
TE D
8.7
1
S0042-207X(16)30810-7
DOI:
10.1016/j.vacuum.2016.11.004
Reference:
VAC 7186
To appear in:
Vacuum
Received Date: 11 March 2016 Revised Date:
2 November 2016
Accepted Date: 4 November 2016
Please cite this article as: Yu L, Chen J, Ju H, Dong H, Zhao H, Influence of Al content on microstructure, mechanical and tribological properties of Ti-W-Al-N composite films, Vacuum (2017), doi: 10.1016/j.vacuum.2016.11.004. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Influence of Al content on microstructure, mechanical and tribological properties of Ti-W-Al-N composite films Lihua Yu*, Jian Chen, Hongbo Ju, Hongzhi Dong, Hongjian Zhao
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School of Materials Science and Engineering, Jiangsu University of Science and Technology, Mengxi Road 2, Zhenjiang, Jiangsu Province, 212003, China
Abstract: Ti-W-Al-N films with various Al content (0 at.% ~ 12.4 at.%) were deposited by
SC
reactive magnetron sputtering. The composition, microstructure, mechanical and tribological properties of Ti-W-Al-N films were investigated by EDS, XRD, HRTEM, SEM,
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Nano-indentation, Ball-on-disk tribometer. It is found that Ti-W-Al-N films consist of Ti-W-Al-N phase, Ti2N phase and W2N phase below 2.9 at.% Al. Ti2N phase disappears at 5.6 at.% Al and h-AlN phase forms at 12.4 at.% Al respectively. The hardness firstly increases and then decreases with increasing Al content and the highest hardness is 35.7 GPa at 8.7 at.% Al. At room temperature, the friction coefficient continuously increases,
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whereas the wear rate firstly decreases and then increases with increasing Al content. The lowest wear rate of 1.79×10-8 mm3N-1mm-1 is obtained at 8.7 at.% Al. As the temperature increases from room temperature to 700
, the friction coefficient firstly increases and then
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decreases, while the wear rate gradually increases. The tribological properties of the film depended on the testing temperatures significantly because the testing temperatures
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influenced the hardness, the tribo-films and wear mechanism of the film. Keywords: reactive magnetron sputtering; microstructure; mechanical property; tribological property
1. Introduction
Over the past decade, the development of nanostructured composite films has resulted in considerable improvement in comparison to single hard films (TiN, ZrN, CrN, etc) in terms of their outstanding performance[1-3]. Recently, TiWN films have been widely 1
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applied to resistance transmitters and cutting tools because of their high hardness, excellent corrosion resistance, good adhesion[4-6]. We have previously reported that TiWN composite films revealed a high hardness of 30.7 GPa and had the ability to adapt self
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lubrication due to forming Magnéli phase oxide WO3, which could obviously reduce the friction coefficient and effectively improve tribological properties[7]. However, relative high wear rate and poor oxidation resistance limited performance of TiWN films at high
SC
temperature[8-10]. Studies[11-14] on Ti-Al-N system showed that Al added to the films can effectively improve the oxidation resistance due to the density Al2O3 oxide layer forming on
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the surface of the films. Although the high Al content films showed excellent oxidation resistance, the hardness decreased in terms of h-AlN phase (the hardness value ≤26GPa) forming in the films[15-16].
In this study, Ti-W-Al-N composite films with various Al content were prepared by a reactive magnetron sputtering system to obtain excellent tribological properties and
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oxidation resistance. Previous study showed that Ti-W-Al-N films have better corrosion behavior[17]. However, the tribological performance of Ti-W-Al-N films is seldom studied in detail. The microstructure, mechanical and tribological performance at room/high
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temperature of Ti-W-Al-N films were investigated. In addition, the wear mechanism at high temperature were discussed.
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2. Material and methods In this study, Ti-W-Al-N films with a thickness of about 2 µm were deposited on both
single crystal silicon (100) wafers and polished 304 stainless steel coupons (15 mm×15 mm×2.5 mm) substrates using JGP-450 type reactive magnetron sputtering system. Ti target (99.9 %), W target (99.9 %) and Al target (99.9 %) with a diameter of 75 mm were sputtered by three radio frequency powers. Silicon wafers and polished stainless steel substrates were ultrasonically cleaned in acetone and alcohol for 10 min, respectively. The substrates were 2
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mounted on a substrate holder and installed at a distance of 78 mm from the target. A base pressure of less than 6.0×10-4 Pa was reached prior to all film depositions. The substrates were RF sputter-etched by Ar plasma bombardment at a target power of 40 W to remove the
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surface contaminants. Prior to the Ti-W-Al-N films deposition, a thin Ti adhesion layer, with a thickness of 100 nm, was first deposited by sputtering from Ti target using target power of 150 W. Subsequently, Ti-W-Al-N films were deposited in Ar and N2 mixtures with the gas
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flow of 10 sccm and 2 sccm. During film depositions, Ti and W target power of 250 W and 90 W was fixed and Al target power was fixed for 0, 25, 50, 75 and 100W, respectively. The
bias was used for all depositions.
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working pressure was maintained constant at 0.3 Pa. Neither substrate heating nor substrate
The chemical composition of Ti-W-Al-N films with various Al power targets was investigated by a field emission electron probe microanalyzer (FM-EPMA, JXA-8500F, JEOL, Japan). The microstructure of the films was characterized using Island Ferry X-ray
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6000 X-ray diffraction with monochromatic Cu Kα radiation at a grazing angle of 4° and high resolution transmission electron microscopy (HRTEM) operated at 200 kV. The average grain size of Ti-W-Al-N films was calculated by Scherrer formula (Eq.(1)) using the
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data of the diffraction peaks of TiN (111) and (200), which are belong to the face-centered
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cubic (fcc) TiN pahse.
D = Kγ / Bcosθ
(1)
where K is Scherrer constant (K=0.89), γ is the wavelength of X-ray (γ=0.154056 nm), B is the FWHM of XRD diffraction peak, θ is the diffraction angle. The lattice constant of the films was also calculated using the data of the diffraction peaks of TiN (111) and (200). Scanning electron microscope (SEM, JMS-6480) was used to observe worn surface morphologies of the films after wear tests at high temperature. The thickness was calculated by the cross-sectional SEM image. The hardness of the films were determined using nano 3
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indentation tester system (nano-indenter CPX + NHT + MST), which were equipped with a diamond Berkovich indenter tip (3-side pyramid). The hardness measurements were performed with the maximum applied load of 5 mN to meet the indentation depth less than
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10 % to reduce the effect of Si substrate on the values. 9 repeated indentations were made for each sample. The oxidation resistance of the film was measured using thermogravimetric analysis system (STD-2960,TA Instrument). Due to the inability of the film to be stripped
heated from 150
to 700
at a heating rate of 15
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from the substrate, the film and the silicon substrate were tested together. The sample was /min and 60 ml/min of air to maintain
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an oxidative atmosphere. Ball-on-disk wear tests were carried out to measure the tribological behavior of the films using UMT–2 tribometer with alumina ball counterpart (9.38 mm in diameter). The test counterpart was sliding in a circular path with a radius of 4 mm at a relative velocity of 50 r/min. Each sample was tested for 30 min. The wear rates of the films were measured using Dektak surface profilometer by taking average measurements
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along the wear track. The wear rate (Ws) of the films was calculated by Eq.(2). Ws = C × S /( F × L)
(2)
where Ws is wear rate; S is wear track area; C is perimeter of wear crack; F is the normal
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load; L is sliding length. The residual stresses were calculated by Stoney’s equation (Eq(3))
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using Dektak surface profilometer. σ = Es t s2 (1 / R − 1 / R0 ) /[6(1 − υ s )t f ]
(3)
Where Es is the elastic modulus of the substrate (Es=170 GPa), υs is the Poisson’s ratio of the substrate (υs=0.3), ts is the thickness of the substrate, tf is the thickness of film, R is the curvature of film, R0 is the curvature of Si substrate.
3. Results and discussion 3.1 Chemical composite and microstructure
4
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The chemical compositions of the Ti-W-Al-N films are summarized in Table1. As the Al target power increases from 0 to 100W, the Al content increases linearly from 0 to 12.4 at.%. With the increase of Al content, the lattice constant of TiN phase and grain size of TiN
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phase gradually decrease. This suggests that Ti and W atoms are replaced gradually by the Al atoms forming the substitutional solid solution. The decrease in the grain size suggests that the incorporation of Al could result in the re-nucleate.
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Fig.1(a) shows the XRD patterns of Ti-W-Al-N films with different Al content. It can be seen that fcc-TiN phase, Ti2N phase and W2N phase coexist in the Ti-W-Al-N films when
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the Al content is in the range of 0 at.%-2.9 at.%. When the Al content at 5.6 at.%, Ti2N phase disappeared and the films consisted of fcc-TiN phase and W2N phase. With a further increase in the Al content, h-AlN phase appeared and the films consisted of fcc-TiN phase, h-AlN phase and W2N phase as shown in Fig.1(b)[17]. Further details of the microstructure of Ti-W-Al-N film with 12.4 at.% Al are revealed by HRTEM image as shown in Fig.2.
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Three sets of lattice fringes with a lattice spacing of about 0.235 nm, 0.210 nm and 0.144 nm are observed, which are corresponding to the h-AlN (101), c-TiN (200) and c-W2N (220) respectively.
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The lattice constant and grain size (calculated by Eq(1)) of Ti-W-Al-N films with various Al content are listed in Table 1. The lattice constant and grain size of TiWN film are
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about 0.423 nm and 28.7 nm, respectively. As the increase of Al content, the lattice constant and grain size of Ti-W-Al-N films gradually decrease. When the Al content is less than 8.7 at.%, the lattice constant contracts with the substitution of Ti and W atoms by the smaller size Al atoms in the solid solution. Excessive Al atoms react with nitrogen atoms forming h-AlN phase as the Al content increases to 12.4 at.%. Consistent with the decreasing tendency of the lattice constant, the grain size decreases from 24.8 nm at 2.9 at.% to 11.7 nm at 12.4 at.%. 5
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3.2 Mechanical properties Fig.3 shows the hardness and residual stress of Ti-W-Al-N films with different Al content. It is found that the hardness of Ti-W-Al-N films increases from 30.7 GPa to 35.7
as the Al content further increases to 12.4 at.%.
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GPa as the Al content increases from 0 at.% to 8.7 at.%. The hardness decreases to 32.4 GPa
Many factors influence the hardness of the films. According to the reported studies, the
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hardness enhancement are mainly attributed to solid solution strengthening[18] and grain size refinement[19-20]. Besides, it is also imputed to the compress residual stress[21] in the
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films. In the Ti-W-Al-N films, Ti atoms and W atoms are replaced by Al atoms forming substitutional solid solution. As increase of the Al content, the grain size refines and there exhibits compress residual stress in the films. So the hardness enhancement of the films is mainly associated with solid solution strengthening, grain size refinement and the compress residual stress. As the Al content increases to 12.4 at.%, the hardness decreases due to the
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saturation of Al content weakening solid solubility strengthening and causing the compress stress relaxation. In addition, the appearance of the AlN phase in the film also leads to the decrease of the hardness of the film when the Al content is 12.4 at.% because the hardness
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of the binary AlN film deposited under the same condition is about 21 GPa.
3.3 Tribological properties
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Fig.4 shows the friction curves, the average friction coefficient and wear rate of the
Ti-W-Al-N films with different Al content at room temperature. It can be seen from Fig.4(a) that the friction slightly increases before 200 s, and then decreases and gradually stabilizes. With the increase of Al content, the friction coefficient of the films gradually increases, whereas the wear rate decreases first and then increases. The lowest wear rate of 1.79×10-8 mm3N-1mm-1 is obtained at 8.7 at.%, as shown in Fig.4(b). The tribo-film plays an important role in the tribological properties of the films and the 6
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phenomenon of tribo-oxidation can be observed in wear test at room temperature. Fig.5 shows the XRD patterns of the Ti-W-Al-N films with different Al content after wear test at room temperature. As the Al content is less than 10.39 at.%, WO3 is detected and the
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diffraction peaks of WO3 gradually weakens along with the increase of Al content. When the Al content is higher than 8.7 at.% , no WO3 is detected in the films.
In order to study the tribological properties of Ti-W-Al-N films at high temperature, the ball-on-disk wear test of the film with 8.7 at.% Al has been done at 200
, 500
SC
and 700
, 400
,and the average friction coefficient and wear rate at different temperatures are
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showed in Fig.6(a). In order to study the influence of the Al element on the tribological properties of Ti-W-Al-N film at elevated temperatures, the friction coefficient and wear rate of Ti-W-N film at elevated temperatures are also shown in Fig. 6(b). For Ti-W-Al-N film, the friction coefficient increases first and then decreases, and reaches a maximum value of . As the temperature sequentially increases to 500
0.68 at 400
, the friction coefficient
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sharply decreases to 0.46. With the temperature further increase to 700
, the friction
coefficient decreases to 0.39. However, the wear rate gradually increases as the temperature increases, and reaches a maximum value of 3.24×10-7 mm3N-1mm-1 at 700
. The
temperatures.
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combination of Al into Ti-W-N film could improve the tribological properties at elevated
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Fig.7 shows the XRD patterns of the Ti-W-Al-N film (8.7 at.% Al)after wear test at
200
,400
,500
and 700
. It is found that no oxide appears at 200
and 400
the oxide of TiO2, Al2O3 and WO3 appear as the temperature increases to 500
,while
, indicating
that the film starts to oxide. With a further increase of the temperature, the diffraction peaks of the oxide phase become stronger and more, indicating a further oxidation of the film. In order to further verify the oxidation resistance of the Ti-W-Al-N films, the thermogravimetric analysis of the Ti-W-Al-N film (8.7 at.% Al) has been done and the TG 7
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curve is presented in Fig.8. The previous study[22] indicates that Al atoms oxidize forming amorphous Al2O3 at lower temperature (below 500
). With increase of the temperature, the
crystalline Al2O3 forms. As shown in the Fig.8, the weight of the film slowly increases as , which indicates that the
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the temperature increases when the temperature below 430
amorphous Al2O3 forming in the film as a dense protective layer to inhibit the deeper oxidation in the film [22]. When the temperature increases to 430
, the weight of the
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Ti-W-Al-N film dramatically increases due to the formation of the crystalline Al2O3. Then oxygen can easily diffuse inward the films through the grain boundary of the crystalline
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Al2O3 accelerating the film oxidation accompanied with a further formation of TiO2, WO3 and Al2O3, causing the rapid increase of the weight [22].
The hardness of the Ti-W-Al-N film (8.7 at.% Al) as a function of the annealed temperature is shown in Fig.9. With increasing annealing temperature to 400
, a slight
decrease of the hardness can be observed. Since neither variation of the microstructure nor
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oxidation is observed as shown in Fig.7, the decrease of the hardness could be attributed to the compressive stress relaxation, which is induced by the heat [23]. As the temperature is above 500
, the hardness decreases. This is due to that Ti-W-Al-N film obviously oxidizes
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and forms a large number of lower hardness oxides, TiO2, Al2O3, and WO3, which leads to the obvious decrease of the hardness.
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According to the previous studies, WO3 can reduce the friction coefficient in terms of
its layered structure [10]. The decrease of WO3 as the increase of the Al content can be observed in Fig.7, which is mainly attributed to amorphous Al2O3 formed on the surface of the films as a protective layer to inhabit oxygen diffusing inward the films. Then, the self-lubricating performance is weakened due to the decrease of WO3, which leads to a gradual increase of the friction coefficient. The wear rate is closely related to the hardness and the phase structure as reported in many studies[6,24]. High hardness materials are 8
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difficult to be worn. On the contrary, the layered structure materials could be worn easily because of their low shear strength. In this study, the wear rate gradually decreases as increase of the Al content when Al content is low than 8.7 at.%, which is attributed to the
hardness sharply decreases, the wear rate of the film increases.
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increase of the hardness and the decrease of WO3. With a further increase of Al content, the
The friction coefficient of the Ti-W-Al-N film (8.7 at.% Al) gradually increases as the . This may be due to the decreases of
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temperature increases from room temperature to 400
moisture[25] and the decrease of the self-lubrication oxide WO3. As the temperature , the crystalline Al2O3 forms in the film as shown in Fig.7, which
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increase to 500
accelerates the oxidation of the film resulting in the increase of the WO3[8]. Therefore, the friction coefficient widely decreases. The wear rate slightly increases as the temperature , which is the enhancement in oxidation
increases from room temperature to 400
resistance due to the formation of amorphous Al2O3 and the slightly decrease of the hardness
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in this temperature range. When the temperature increases to 500
and 700
, the
crystalline Al2O3 forms and accelerates the oxidation of the film leading to the sharp decrease of the hardness as shown in Fig.9, therefore, the wear rate rapidly increases.
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Fig.10 shows the wear track morphology of the TiWN film and the Ti-W-Al-N film (8.7 at.% Al) at 400
, 500
and 700
. It can be found that the wear track of the
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Ti-W-Al-N film is shallower in depth and lower in roughness than TiWN film’s at 400
as
shown in Fig.10(a) and Fig.10(b). This wear mechanism is slight adhesion and moderate abrasion. As the temperature increases to 500
, the TiWN and Ti-W-Al-N films exhibit
deeper wear track and worn spalling phenomena occurred on the surface of the films as shown in Fig.10(c)and Fig.(d), which is mainly due to the film oxidation and the formation of the susceptibly worn oxides. Some oxides are attached with the counterpart and transfer with the grinding ball causing the peeling off. The wear mechanism is a mixture of heavy 9
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adhesion and tribo-oxidation. Compared with 400
and 500
, as the temperature is 700
,
the wear tracks of the TiWN and Ti-W-Al-N films obviously become wider, and deeper. Serious crack appeared on the surface of the wear tracks and the films have been almost
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worn away as shown in Fig.10(e) and Fig.10(f).The wear mechanism is tribo-oxidation at this temperature.
4. Conclusion
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The Ti-W-Al-N films with different Al content were deposited by reactive magnetron
sputtering and the effects of Al content on the microstructure, mechanical properties and
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tribological properties of Ti-W-Al-N films were studied. The main results could be concluded as follows:
1) Ti-W-Al-N films consist of TiN phase, Ti2N phase and W2N phase below 2.9 at.% Al. Ti2N phase disappears at 10.4 at.% Al and h-AlN phase forms at 12.4 at.% Al respectively.
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2) The Ti-W-Al-N film containing 8.7 at.% Al has the highest hardness of 35.7GPa. The hardness enhancement of the films is mainly associated with solid solution strengthening, grain size refinement and the compress residual stress.
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3) At room temperature, the wear rate decreases first and then increases, whereas the friction coefficient gradually increases with increasing Al content at room temperature. The
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lowest wear rate of 1.79×10-8 mm3N-1mm-1 is obtained at 8.7 at.% Al. 4) For the Ti-W-Al-N film with 8.7 at.% Al, high temperature wear tests show that as
the temperature increases from room temperature to 700
, the friction coefficient firstly
increases and then decreases, while the wear rate gradually increases. The tribological properties of the film depended on the testing temperatures significantly because the testing temperatures influenced the hardness, the tribo-films and wear mechanism of the film.
Acknowledgments 10
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Supported by the National Natural Science Foundation of China (51374115, 51574131) and combined study of Industry University Research of Jiangsu Province (BY2013066-11).
References
produced by magnetron sputtering, Thin Solid Films 317 (1998) 351-355.
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[1] L. Cunha, M. Andritschky, L. Robouta, et al., Corrosion of TiN, (Ti,Al)N and CrN hard coatings
[2] Hongbo Ju, Junhua Xu, Microstructure, oxidation resistance, mechanical and tribological properties
SC
of Ti-Y-N films by reactive magnetron sputtering, Surface and Coatings Technology 283 (2015) 311-317. [3] J.H. Hsieh, T.H. Yeh, C. Li, et al., Antibacterial properties of TaN-(Ag,Cu) nanocomposite thin films, Vacuum 87 (2013) 160-163.
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[4] S. Zhou, W. Liu, H. Liu, et al., Structural and electrical properties of Ti-WN thin films deposited by reactive RF sputtering, Physics Procedia 18 (2011) 66-72.
[5] J.C. Caicedo, L. Yate, J. Montes, Improving the physicochemical surface properties on AISI D3 steel coated with TiWN, Surface and Coatings Technology 205 (2011) 2947-2953. [6] B. Tian, W. Yue, Z. Fu, et al., Microstructure and tribological properties of W-implanted PVD TiN
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coatings on 316L stainless steel, Vacuum 99 (2014) 68-75.
[7] Lihua Yu, Hongzhi Dong, Junhua Xu, Effect of W content on microstructure, mechanical and tribological properties of Ti1−xWxN composite films, Materials Science and Engineering of Powder Metallurgy 19 (2014) 812-817.
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[8] G. Gassner, P.H. Mayrhofer, K. Kutschej, et al., Magnéli phase formation of PVD Mo–N and W–N coatings, Surface and Coatings Technology 201 (2006) 3335-3341.
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[9] G.S. Fox-Rabinovich, K. Yamamoto, S.C. Veldhuis, et al., Self-adaptive wear behavior of nano-multilayered TiAlCrN/WN coatings under severe machining conditions, Surface and Coatings Technology 201 (2006) 1852-1860. [10] T. Aizawa, A. Mitsuo, S. Yamamoto, et al., Self-lubrication mechanism via the in situ formed lubricious oxide tribofilm, Wear 259 (2005) 708-718. [11] D. McIntyre, J.E. Greene, G. Hakansson, et al., Oxidation of metastable single-phase polycrystalline Ti0.5Al0.5N films: Kinetics and mechanisms, Journal of Applied Physics 67 (1990) 1542-1553. [12] K. Chakrabarti, J.J. Jeong, S.K. Hwang, et al., Effects of nitrogen flow rates on the growth 11
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morphology of TiAlN films prepared by an rf-reactive sputtering technique, Thin Solid Films 406 (2002) 159-163. [13] K. Kutschej, P.H. Mayrhofer, M. Kathrein, et al., Structure, mechanical and tribological properties of
RI PT
sputtered Ti1–x AlxN coatings with 0.5≤x≤0.75, Surface and Coatings Technology 200 (2005) 2358-2365.
[14] Chunyan Yu, Shebin Wang, Xiaoding Yin, et al., Study on high-temperature oxidation resistance of CrAlN coatings, Rare Metal Materials and Engineering 38 (2009) 1015-1018.
SC
[15] M. Brizuela, A. Garcia-Luis, I. Braceras, et al., Magnetron sputtering of Cr(Al)N coatings: Mechanical and tribological study, Surface and Coatings Technology 200 (2005) 192-197.
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[16] Yunke Ge, Xiaobo Gu, Lihua Yu, et al., Investigation of Phase Structure and Properties of (Zr, Al)N Coatings, Development and Application of Materials 23 (2008) 21-25.
[17] Christopher M.A. Brett, Albano Cavaleiro, A comparison of the electrochemical behavior of W-M-N (M=Ni, Ti, Al) thin film coatings on high speed steel, Thin Solid Films 322 (1998) 263-273. [18] E. Ertuerk, O. Knotek, W. Burgmer, et al., Ti(C, N) coatings using the arc process, Surface and
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Coatings Technology 46 (1991) 39-46.
[19] T. Yamamoto, M. Kawate, H. Hasegawa, et al., Effects of nitrogen concentration on microstructures of WNx films synthesized by cathodic arc method, Surface and Coatings Technology 193 (2005) 372-374.
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[20] W.Y. Wu, C.H. Wu, B.H. Xiao, et al., Microstructure, mechanical and tribological properties of CrWN films deposited by DC magnetron sputtering, Vacuum 87 (2013) 209-212.
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[21] L. Zhang, H. Yang, X. Pang, et al., Microstructure, residual stress and fracture of sputtered TiN films, Surface and Coatings Technology 224 (2013) 120-125. [22] J. Lin, B. Mishra, J.J. Moore, et al., A study of the oxidation behavior of CrN and CrAlN thin films in air using DSC and TGA analyses, Surface and Coatings Technology 202 (2008) 3272-3283. [23] T. Polcar, A. Cavaleiro, Structure, mechanical properties and tribology of W–N and W–O coatings, International Journal of Refractory Metals and Hard Materials 28 (2010) 15-22. [24] X. Chen, Z. Wang, S. Ma, et al., Microstructure, mechanical and tribological properties of Ti–B–C–N films prepared by reactive magnetron sputtering, Diamond and Related Materials 19 (2010)
12
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1336-1340. [25] G. Cheng, D. Han, C. Liang, et al., Influence of residual stress on mechanical properties of TiAlN
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EP
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SC
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thin films, Surface and Coatings Technology 228 (2013) S328-S330.
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Figure captions Fig.1 XRD patterns of TiWAlN films with different Al content Fig.2 HRTEM image of TiWAlN film with 12.4 at.% Al
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Fig.3 Hardness and residual stress of TiWAlN films with different Al content
Fig.4 The friction curves (a) and friction coefficient and wear rates (b) of TiWAlN films at room temperature
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Fig.5 XRD patterns of TiWAlN films after wear test at room temperature
Fig.6 Friction coefficient and wear rate of TiWAlN film at different temperatures(a)
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TiWAlN film at 8.7 at.% Al; (b) TiWAlN film at 0 at.% Al
Fig.7 XRD patterns of TiWAlN films after wear test at different temperatures Fig.8 TG curve of TiWAlN film with 8.7 at.% Al
Fig.9 Hardness of TiWAlN films (8.7 at.% Al ) as a function of annealed temperature Fig.10 Wear tracks morphology of TiWN films and TiWAlN films at high temperature (a), 500
(c) and 700
(e); wear tracks
morphology of TiWAlN composite films at 400
(b), 500
(d) and 700
(f))
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(wear tracks morphology of TiWN films at 400
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EP
Fig.1
Fig.2
1
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Fig.4
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EP
TE D
Fig.3
Fig.5
2
AC C
EP
TE D
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SC
Fig.6
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Fig.7
3
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SC
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Fig.9
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Fig.8
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EP
TE D
Fig.10
4
(b)
(c)
(d)
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(a)
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(f)
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EP
TE D
(e)
5
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1. TiWAlN films exhibit various microstructures depending on different Al content. 2. The film with 15.9 at.% Al has the highest hardness and the lowest wear rate at
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25℃.
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TE D
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3. The TiWAlN films with Al have higher oxidation resistance temperature.
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Table caption Table 1 Chemical composition, lattice constant and average grain size of Ti-W-Al-N films Table 1 Chemical composition (at.% )
Al target (W)
Ti
W
Al
N
O
Lattice
Average
constant
grain
(nm)
Size
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Power of
37.7
20.5
0
39.4
2.4
0.4230
28.7
25
32.5
18.5
2.9
43.2
2.9
0.4218
24.8
50
30.8
17.3
5.6
43.8
2.5
0.4214
19.2
75
26.4
15.5
100
23.9
11.9
SC
0
M AN U
（nm）
46.7
2.7
0.4200
12.3
12.4
48.1
3.7
0.4199
11.7
AC C
EP
TE D
8.7
1