- Email: [email protected]
TiSiN coatings synthesized by cathodic arc evaporation
Accepted Manuscript Tribological and mechanical properties of multilayered TiVN/ TiSiN coatings synthesized by cathodic arc evaporation
Yin-Yu Chang, Hung Chang, Liang-Jhan Jhao, Chih-Cheng Chuang PII: DOI: Reference:
S0257-8972(18)30158-0 doi:10.1016/j.surfcoat.2018.02.040 SCT 23111
To appear in:
Surface & Coatings Technology
Received date: Revised date: Accepted date:
6 November 2017 17 January 2018 12 February 2018
Please cite this article as: Yin-Yu Chang, Hung Chang, Liang-Jhan Jhao, Chih-Cheng Chuang , Tribological and mechanical properties of multilayered TiVN/TiSiN coatings synthesized by cathodic arc evaporation. The address for the corresponding author was captured as affiliation for all authors. Please check if appropriate. Sct(2017), doi:10.1016/ j.surfcoat.2018.02.040
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.
ACCEPTED MANUSCRIPT Tribological and mechanical properties of multilayered TiVN/TiSiN coatings synthesized by cathodic arc evaporation Yin-Yu Chang1*, Hung Chang1, Liang-Jhan Jhao1, Chih-Cheng Chuang1 1
Department of Mechanical and Computer-Aided Engineering, National Formosa University, Taiwan
Abstract
PT
The flexibility of the physical vapor deposition (PVD) method in obtaining
RI
coatings with a delicate control at a nanometric level provides superior properties.
SC
Among these coatings, transition metal nitride coatings based on Ti, Si, Al and V,
NU
such as TiAlN, TiSiN and TiVN, have been attracting great interest for industrial applications as protective coating materials due to their high hardness, wear resistance
MA
and tribological performance. In this study, TiVN, TiSiN and multilayered TiVN/TiSiN coatings were deposited onto tungsten carbide tools using cathodic-arc
PT E
D
evaporation (CAE) system. During the coating process of TiVN/TiSiN, TiN was deposited as an interlayer to enhance adhesion strength between the coatings and
CE
substrates. The main objective of the present work is to investigate the effect of TiVN on the microstructure, mechanical properties and tribological performance of the
AC
deposited TiVN/TiSiN coatings by regulating the bias voltage during the coating process. The multilayered TiVN/TiSiN coatings exhibited higher hardness of 35~37 GPa, indicating higher resistance against plastic deformation compared to TiVN and TiSiN. The result of ball-on-disc wear tests and end milling tests of 7000 series Al alloys showed that the lowest wear rate and the longest tool life were obtained for the multilayered TiVN/TiSiN coating deposited at high bias voltage of 180 V, which was 1
ACCEPTED MANUSCRIPT
significantly better than that of the monolayered TiSiN.
AC
CE
PT E
D
MA
NU
SC
RI
PT
Keywords: hard coating; TiVN; TiSiN; mechanical; multilayer; tribological
2
ACCEPTED MANUSCRIPT
1. Introduction The superior tribological properties of materials are mainly governed by high hardness, improved resistance to plastic deformation and surface inertness. Hard coatings reduce the tool temperature by reducing the friction between chip and rake
PT
face of a tool. Additionally, low chemical reactivity of coatings with workpiece
RI
materials protects against welding and thus reduces the adhesive wear. The result of
SC
all these effects shows that coated tools can operate at higher cutting speed and higher
NU
feed rate. Thus hard coating expands the safe zone of cutting tools by minimizing the built-up edge (BUE) formation and crater wear. In this aspect, micro- and
MA
nano-structured hard coatings have been widely used as protective tool coatings and considered to be crucial in the production of mechanical parts and tools, owing to
PT E
D
their high hardness, thermal stability and wear resistance properties [1-6]. In early researches, TiSiN and TiAlN have gained much attention as substitutes for traditional
CE
binary nitride coatings with regard to industrial applications involving wear protection, cutting tools and machinery components. Properties of simple TiN can be greatly
AC
enhanced by addition of other elements, such as Al or Si. Incorporation of Al in fcc-TiN structure leads to formation of TiAlN coatings characterized by high hardness (around 32 GPa) and high oxidation resistance (up to 800 °C). This enables TiAlN coatings synthesized by physical vapor deposition (PVD) to be a material with a broad
range
of
applications,
especially
as
cutting
tools
for
machining
difficult-to-machine materials under harsh environments [7-9]. Moreover, the addition 3
ACCEPTED MANUSCRIPT
of Si and Al into TiN to form TiSiN and TiAlSiN results in coatings with superior properties compared to TiN and TiAlN with regard to thermal stability and mechanical performance [10-18]. These multicomponent nitride coatings have been reported to have superior wear resistance because of the formation of stable oxide
PT
layers on the worn surfaces. However, the oxides formed at the tribo-contact area are
RI
not always effective in reducing friction and wear of materials, which depends on
SC
morphology and chemistry of oxides. The addition of vanadium into TiN and TiAlN
NU
to form TiVN and TiAlVN provided improved tribological performance in the increasingly severe working conditions, such as the high working temperatures
MA
through the possible formation of lubricious surface oxides [19-22]. The improvement of tribological performance of protective coatings can be
PT E
D
achieved by increasing hardness and fracture toughness. A possible approach involves the replacement of monolayered coatings by multilayers to meet the above
CE
requirement. Multilayered architecture acts as a crack inhibitor and thereby improves the fracture resistance [23]. Multilayered coatings composed of different layers show
AC
superior mechanical strength, such as hardness and wear resistance, as compared to monolayered coatings due to their specific interfaces. Especially, TiN and TiVN based multilayered coatings such as TiN/VN, TiN/TiAlN and CrAlSiN/TiVN systems have been widely studied, and they exhibit superior mechanical and tribological properties than in the form of a single layer. Such properties in multilayered structure depend mostly on the microstructure of each layer, interfacial adhesion and thickness of each 4
ACCEPTED MANUSCRIPT
layer [2, 24-27]. The nanoscale-multilayered coatings showed that nanoscale strain optimization by multilayers with different periodic bilayer thicknesses, is an effective way to make coating materials possessing good mechanical and tribological properties superior to those of the constituents in the multilayers [28, 29]. In this study, cathodic
PT
arc evaporation (CAE) ion plating system with TiV and TiSi alloy targets was used for
RI
the deposition of TiVN, TiSiN and TiVN/TiSiN multilayered coatings. The
SC
tribological properties and cutting performance of TiVN, TiSiN and TiVN/TiSiN
NU
multilayered coatings were analyzed.
MA
2. Experimental details
TiVN, TiSiN and multilayered TiVN/TiSiN coatings were deposited using a
PT E
D
CAE system (YG-7850, Surfwell Co., Taiwan) on polished tungsten carbide samples (WC-Co, HV ~ 1600) and standard tungsten carbide end mills (diameter= 6 mm, 2
CE
flutes) at temperature of 280-320 °C. Pure Ti, TiV (40 at.% of Ti and 60 at.% of V) and TiSi (80 at.% of Ti and 20 at.% of Si) alloy targets with diameter of 100.5 mm
AC
were used for the deposition. TiV and TiSi alloy targets were arranged on opposite sides of the chamber. This configuration prevented significant intermixing of the metal vapor arriving at the cathodes. The samples were placed on a movable sample holder, which was fixed perpendicular to the target kept at a distance of 170 mm, and the rotation speed was 4 rpm. Before deposition, a combination of rotary and turbomolecular pumps were used to achieve a base pressure of ∼1 × 10−3 Pa in the 5
ACCEPTED MANUSCRIPT
vacuum chamber. Substrates were cleaned again by Ar ion bombardment using a bias voltage of -800 V for 20 min. The cathode current of the targets was 70~80 A to control the composition of the coatings. For the TiVN and TiSiN coatings, Ti and TiN was deposited as interlayers. The total N2 pressure was maintained at 3.2 Pa, and
PT
applied bias voltage was -120 V. For the deposition of multilayered TiVN/TiSiN
RI
coatings, TiN and TiVN were used as the bottom interlayers to improve the adhesion
SC
strength between the coating and substrate interfaces, and then TiVN/TiSiN
NU
multilayers were deposited. The utilization of substrate bias voltage to accelerate the sputtered ions in sputtering plasmas is an effective way to control the properties of
MA
coating. Two kinds of TiVN/TiSiN coatings were prepared using a low bias voltage of -30 V (denoted as TiVN/TiSiN-LB) and a high bias voltage of -180 V (denoted as
PT E
D
TiVN/TiSiN-HB). The deposition time was 50 minutes. The crystallography of TiVN, TiSiN and multilayered TiVN/TiSiN coatings was
CE
characterized by X-ray diffraction (D8 Discover, Bruker Inc.) using Cu Kα radiation (λ = 0.154 nm). The diffractometer was operated at 40 kV and 1 mA and a step size of
AC
0.02° was maintained. It was performed at a low glancing incidence angle of 2o allowing identifying the coating structure. The x-ray beam incidence angle on the thin film sample was fixed while the detector was moved along the goniometer circle in the 2θ range between 30° and 80° to obtain the diffraction profile of reflecting (hkl) lattice planes. The coating morphology and microstructure were investigated by using a JEOL JSM-6700F field emission scanning electron microscope (FESEM) and a 6
ACCEPTED MANUSCRIPT
JEM-ARM200FTH field emission transmission electron microscope (FETEM). Focused ion beam (FIB, SMI3050, Seiko Instruments Inc.) was performed for TEM sample milling. The obtained cross-section thin specimens were finally attached to a copper grid suitable for TEM observation.
PT
The adhesion strength of the coated samples was evaluated using the Rockwell
RI
C indentation (HR-200, Mitutoyo Taiwan Co.) test with an applied load of 150 kg
SC
according to the ISO 26443 standard. The Rockwell indenter was equipped with a
NU
spheroconical diamond tip with a radius of 200 μm and an angle of 120°. The indents were inspected with an optical microscope (100 × magnification). Hardness of the
MA
films were obtained using XP-MTS nano-indentation with a Berkovich indenter, under load-unloading condition, and measured as a function of indenter displacement
PT E
D
using continuous stiffness measurement method. In order to minimize the influence of substrate on the measurement of mechanical properties of the coatings, the maximum
CE
indentation depth was approximately 10% of the coating thickness. A constant Poisson's ratio of ν = 0.25 was assumed for the deposited coatings. On the basis of
AC
these measurements, the force-displacement curve was obtained. From the load-displacement data, hardness can be determined. Five indents were conducted to obtain the average hardness values. The tribological behavior of the coatings was evaluated using a tribometer in ball-on-disc mode (CSM Instruments, Switzerland). A tungsten carbide ball with a diameter of 6.35 mm was used as the sliding counter body. For each measurement, the applied load and sliding speed were kept constant at 5 N 7
ACCEPTED MANUSCRIPT
and 30 mm/s, respectively. In order to meet the harsh environment in tribological sliding, these experiments were carried out in an ambient atmospheric condition without lubricant. The wear track morphology and wear volumes were analyzed and determined using a confocal laser-scanning microscope ((VK-X100, Keyence Inc.).
PT
For the machining experiment, the workpiece material AA7003 Al alloy (tensile
RI
strength= 380 MPa) was machined by the coated end mills (∅8 mm, 2 flutes). The
SC
cutting tests were carried out by dry milling using a 3-axis CNC milling machine (B8,
NU
Takumi Machinery Co., Ltd.). The cutting speed (Vc) was 400 m/min, depth of cut (ap) was 0.5 mm, and feed rate (fz) was 0.013 mm/tooth. Compressed air was
MA
supplied during the cutting experiment. Tool wear was measured using a microscope after a specific machining time period. The wear morphologies of the cutting edge
PT E
D
were also examined with a 3D laser scanning microscope (VK-X100, Keyence Inc.).
3. Results and discussion
CE
3.1 Microstructure characterization
AC
The crystal structures of the TiVN, TiSiN and multilayered TiVN/TiSiN (TiVN/TiSiN-LB and TiVN/TiSiN-HB) coatings examined by glancing X-ray diffraction (XRD) are shown in Fig. 1. All the samples are composed of typical cubic B1-NaCl structures. The diffraction peaks of TiVN were located at 36.72o, 42.96o, 62.38o and 74.70o, which corresponding to (111) (200), (220) and (311) planes. The lattice parameter of the TiVN was 0.421 nm, which was between the values of cubic TiN (0.424 nm, JCPDF file No.: #870629) and VN (0.414 nm, JCPDF file No.: 8
ACCEPTED MANUSCRIPT
#897381). The deposited TiSiN coating had only TiN B1-NaCl crystallite structure with a lattice parameter of 0.426 nm, and no peaks of crystalline Si3N4 were detected. The most important feature is that the XRD patterns exhibit only one group of peaks of fcc structure indicating a single phase solid-solution nitride formation rather than
PT
the co-existence of respective crystalline nitrides [14, 30-33]. The multilayered
RI
TiVN/TiSiN-LB and TiVN/TiSiN-HB coatings also exhibited B1-NaCl crystal
SC
structure. The major peaks corresponding to the (111), (200) and (220) planes for the
NU
NaCl type of crystalline structure were observed. The stabilization of the cubic phase is due to TiVN/TiSiN growth on cubic TiN and TiVN interlayers. In the multilayers,
MA
various growth directions of FCC grains show up, implying the coherent structure formed by successive stack of TiVN and TiSiN. The XRD peaks tended to shift to
PT E
D
lower diffraction angle as the bias voltage increased. Similar results were found in the previous studies [31, 34-36]. The competition in atomic peening, adatom mobility and
CE
resputtering with increasing bias voltage controlled the microstructure of coatings. The atomic peening led to re-arrangement of the lattice atoms and induces stress into
AC
the coating. The intensive ion bombardment induced collisions in adatoms and a higher mobility of adatoms. Such thermally-induced increase in the ad-atom mobility induces growth in those crystallographic directions [36-38]. Fig. 2 showed fractured cross-sectional FESEM images of the TiVN, TiSiN and multilayered TiVN/TiSiN (TiVN/TiSiN-LB and TiVN/TiSiN-HB) coatings. It revealed columnar microstructure of the coating. Columnar gains are oriented in a 9
ACCEPTED MANUSCRIPT
way that the longer axes of the grains are parallel to the growth direction of the coating. The columnar microstructure is typical for the coatings deposited at low gas pressures and low temperatures compared to melting point. Assisted by the EDS at the same time, the deposited TiVN had a TiN interlayer and a transition layer (Ti-rich
PT
TiVN). The deposited TiSiN had a TiN interlayer and a transition layer (Ti-rich
RI
TiSiN). Distinct interfaces can be seen at the boundaries between transition layer and
SC
the top TiSiN layer. No obvious discontinuity in the grain boundary of the associated
NU
columnar grain can be seen. In this TiSiN, addition of Si inhibited the grain growth and induced grain re-nucleation which resulted in compact and dense structure [13, 18,
MA
39-42]. The deposited TiVN/TiSiN-LB and TiVN/TiSiN-HB coatings had a TiN interlayer and 2 transition layers, which were deposited by co-evaporation of Ti, TiV
PT E
D
and TiSi targets in a nitrogen environment. Deposited at a high bias voltage of -180 V, the top TiVN/TiSiN layer of TiVN/TiSiN-HB showed fine dense columnar structures.
CE
The high resolution TEM (HRTEM) images of the TiVN/TiSiN-LB and TiVN/TiSiN-HB multilayered coatings are presented in Fig. 3. The HRTEM
AC
micrograph demonstrated the nanocrystalline structure of the deposited TiVN/TiSiN. The bright-field atomic fringes were visible in all the grains. The lamellar structure can be observed. The white layer is TiSiN, and the black layer is TiVN, respectively. The top layer of the TiVN/TiSiN coating reveals a multilayered structure with stacking of TiVN and TiSiN layers. Measured from TEM observation, the average periodic bilayer thickness (one layer of TiVN and one layer of TiSiN) of 10
ACCEPTED MANUSCRIPT
TiVN/TiSiN-LB deposited at -30 V was about 5.2 nm, and the layer thickness ratio of TiVN to TiSiN is 1.08, which showed the thickness of TiVN and TiSiN was similar. Interfaces between TiVN and TiSiN are coherent. The same crystal structure of TiVN and TiSiN and small mismatch between the lattices showed a good condition for
PT
epitaxial growth. For the TiVN/TiSiN-HB, measured by EDS, the black layer
RI
contained small fraction of Si (~4 at.%). Deposited at high bias voltage of -180 V,
SC
TiSiN and TiVN easily inter-diffused to each other to form composite TiVSiN. The
NU
average periodic bilayer thickness (one layer of TiVSiN and one layer of TiSiN) of TiVN/TiSiN-HB deposited at -180 V was about 5 nm, which showed a little smaller
MA
than the TiVN/TiSiN-LB. The TiVN/TiSiN-HB exhibited a higher layer thickness ratio of TiVSiN to TiSiN of 4.1. The thickness of TiSiN layer decreases to ~0.9 nm
PT E
D
probably because of the re-sputtering effect of TiSiN and the inter-diffusion effect under high bias voltage. Similar results were found in (Cr:Cu)-DLC and CrN/AlBN
CE
multilayered films using CAE at high bias voltage [43, 44]. The result suggested the fundamental nature of ion bombardment during deposition at different bias voltages
AC
of -30 V and -180V, in which the energetic particle impingement of different TiVN and TiSiN played an important role in the evolution of the deposited multilayers.
3.2 Mechanical, tribological and cutting performances TiVN, TiSiN and multilayered TiVN/TiSiN coatings The adhesion strength of all the TiVN, TiSiN and multilayered TiVN/TiSiN 11
ACCEPTED MANUSCRIPT
coated samples were investigated using the Rockwell indentation test, as shown in Fig. 4. Excepted TiSiN, all the other TiVN and multilayered TiVN/TiSiN coatings showed that cone cracks developed beneath the indenter followed by radial cracks around the indentation. The radial cracks without delamination indicated strong adhesive strength
PT
between coating and substrate, and the adhesion strength in this case was evaluated to
RI
class 1. The TiSiN showed that ring cracks and partial delamination were found
SC
around the indentation, and it exhibited poor adhesion strength, which was evaluated
NU
as the criteria of class 2. Fig. 5 shows the measured hardness (H), Young’s modulus (E) and H3/E⁎2 ratio of the TiVN, TiSiN and multilayered TiVN/TiSiN-LB and
MA
TiVN/TiSiN-HB coatings. The hardness of the deposited TiVN, TiSiN coating was 25±0.3 GPa and 34±0.5 GPa, respectively. The Young’s modulus of the deposited
PT E
D
TiSiN was 293 ±16 GPa, and it was similar to that of TiVN (298 ±15 GPa). The multilayered TiVN/TiSiN-LB and TiVN/TiSiN-HB had higher values of Young’s
CE
modulus (305~315 GPa). The results showed that the multilayered coatings of TiVN/TiSiN possessed higher hardness than those of individual TiVN and TiSiN
AC
coatings. The multilayered TiVN/TiSiN-HB coating deposited at high bias voltage of -180 V exhibited the highest hardness of 37±0.8 GPa. As compared to TiVN/TiSiN-LB, the higher hardness of the TiVN/TiSiN-HB is due to the increasing bias voltage in a proper range, leading to effective ion bombardment and resulting in dense structure formed in the TiVN/TiSiN-HB. Similar results were found in the study of TiSiN coatings with different bias voltages [31]. It revealed that the presence of the 12
ACCEPTED MANUSCRIPT
nanolayered structure of the TiVN/TiSiN could increase the hardness based on the interfacial strengthening of epitaxially grown multilayers combining different strengthening mechanisms, such as Hall-Petch and coherency strain relations for multilayered materials [45, 46]. For the TiVN/TiSiN-HB coating deposited at high
PT
bias voltage of -180 V, it was reasonable to assume that the compositional modulation
RI
from layers V rich in TiVSiN to TiSiN, corresponding to different alloying contents in
SC
the formed solid solution, should also contribute to the enhanced hardness [47].
NU
Previous studies also showed that the multilayered coatings, such as TiN/VN,
monolithic coatings [24, 42, 48].
MA
TiAlN/ZrN and CrN/MoN, possessed higher values of hardness than those of
To evaluate mechanical properties of films and to predict protective features of
PT E
D
coatings, the ratios of hardness to elastic modulus could be used. Both the coating hardness and the elastic modulus have been proposed to play crucial roles in
CE
determining the wear and cracking resistances of the hard coatings. Previous studies had shown that this behavior was expressed by the H/E* or H3/E⁎2 ratio, where H and
AC
E⁎ are the hardness and effective modulus of the coating. E⁎ could be further expressed as E* = E/(1-v2), where E is the elastic modulus, and v is the Poisson ratio (~ 0.25) [49, 50]. With higher H and lower E⁎, the plastic deformation is lower. As shown in Fig. 5(b), the H3/E⁎2 ratio of TiVN and TiSiN was 0.16 and 0.39, respectively. The multilayered TiVN/TiSiN-LB coatings exhibited higher H3/E⁎2 ratio (0.41) than that of TiVN and TiSiN. The H3/E⁎2 ratio showed the highest value of 0.46 13
ACCEPTED MANUSCRIPT
GPa for the multilayered TiVN/TiSiN-HB coating. J. Guo et. al. [51] conformed that a high H/E* value was desirable for the triboligical applications. In this study, the high H3/E⁎2 ratio of the multilayered TiVN/TiSiN-HB could be beneficial to enhance the wear resistance [49, 51-53].
PT
Ball-on-disc tribological tests were performed to evaluate the friction and wear
RI
properties of the TiVN, TiSiN and multilayered TiVN/TiSiN coatings. Fig. 6(a) shows
SC
the relationship between the coefficient of friction (COF) and the sliding distances
NU
under dry sliding conditions. All friction curves exhibit running-in and steady state stages. During the running-in, the COF increase with increasing sliding distance, as a
MA
result of the contact stress variations and the coated surface. The coatings showed similar trends in the evolution of friction coefficient from the beginning until the
PT E
D
initial rapid running-in resulting in rapid increase in COF and then a steady-state wear regime. During the run-in stage, the TiSiN showed the highest COF of ~0.78. The
CE
temporary decrease in friction coefficient after the running-in period was more prominent in the multilayered TiVN/TiSiN-HB than for the other coatings. Fig. 6 (b)
AC
shows the COF and the wear rate of coatings tested at room temperature under dry sliding conditions. The highest average COF was obtained for the TiSiN coated sample with values of 0.66. The TiVN/TiSiN-LB coated sample showed lower COF of 0.6 than that of TiSiN. The introducing TiVN into the TiVN/TiSiN-LB in a multilayered structure consisting of TiVN and TiSiN provided a lubrication effect, and lowered the COF to 0.6. W.-D Münz et al. also reported a lower COF when 14
ACCEPTED MANUSCRIPT
testing superlattice TiAlN/VN samples against polycrystalline alumina counterparts at normal load 5N [54]. V addition successfully reduced the wear rate and friction coefficient of TiSiN system. In their study, the tribolayer consisting mostly of vanadium oxides was formed on the surface of TiVN coating. However, the addition
PT
of silicon had detrimental effect on tribolayer formation during the sliding process.
RI
Fig. 7 showed the SEM image and O mapping of the wear track of TiVN coated
SC
samples after sliding distance of 600 m. The formation of thin tribolayers comprising
NU
lubricious phases such as titanium oxides and vanadium oxides was probably responsible for the lowering COF as compared to TiSiN. The lowest COF was
MA
obtained for the TiVN/TiSiN-HB coating with a value of 0.32, while the COF of TiVN coating was 0.42 due to the low hardness of 25±0.3 GPa. From the result of
PT E
D
microstructure characterization, the TiVN/TiSiN-HB exhibits a higher layer thickness ratio of TiVSiN to TiSiN of 4.1. This TiVSiN in the TiVN/TiSiN-HB may lead to the
CE
lowest COF of 0.32. A similar result showing the surface V-O, Ti-O and Si-O lubricious oxides on the sliding contact zone of TiVSiN can be found in the previous
AC
study by F. Fernandes et. al. [55]. The highest average COF and wear rate were found for the TiSiN coated sample. The TiVN/TiSiN-LB coated sample showed lower COF of 0.6 and lower wear of 4.4x10-7 mm3/Nm than that of TiSiN. The lowest wear rate (0.24x10-7 mm3/Nm) was obtained for the TiVN/TiSiN-HB coated sample due to the highest hardness and lubricious effect of TiVN. It revealed that the wear resistance of TiVN/TiSiN-HB 15
ACCEPTED MANUSCRIPT
coating was the best among the TiVN, TiSiN and multilayered TiVN/TiSiN coatings. Therefore, TiVN/TiSiN-HB provided improved tribological behavior through the complementary properties of surface oxide formation resisting adhesion wear and high hardness against abrasive wear. From the tribological point of view, P. Panjan et
PT
al. [56] also showed that the CrN/CrVN/VN multilayered hard coatings provided a
RI
high potential for application as a wear-resistant and self-lubricating coating. It
SC
suggested that the bulk diffusion of the vanadium through such layer was hindered
NU
and thus the only possible diffusion paths were growth defects as well as voids between the columns. As compared to TiSiN, vanadium-containing coatings exhibited
MA
a different wear mechanism. Polishing wear occurred in TiVN and multilayered TiVN/TiSiN-HB coatings as demonstrated by smooth worn surfaces, as show in Fig. 8.
PT E
D
The wear track of TiVN and multilayered TiVN/TiSiN-HB coatings showed scratches parallel to the relative sliding movement suggesting polishing wear as the dominant
CE
wear mechanism. As compared to TiVN/TiSiN-HB, the lower hardness of TiVN resulted in the higher wear rate. In addition to the highest hardness of
AC
TiVN/TiSiN-HB resisting the abrasion wear, the wear track of TiVN/TiSiN-HB is smooth and free of longitudinal micro-grooves. Therefore, the multilayered TiVN/TiSiN-HB possessed the lowest wear rate. In this study, TiVN, TiSiN and multilayered TiVN/TiSiN were deposited on the tungsten carbide cutting tools, and the cutting tests were conducted on 7003 aluminum alloy by dry milling at high cutting speed of 400 m/min. The 16
ACCEPTED MANUSCRIPT
challenge in cutting such aluminum alloy materials is the pronounced adhesion of the workpiece material to the cutting edge leading to early blunting when the edge is completely covered. Fig. 9 shows the relationship between cutting length and average flank wear obtained with different tools. Except the multilayered TiVN/TiSiN-HB, the
PT
average flank wear increased rapidly with increasing cutting length before the cutting
RI
length of 13 m. The uncoated tool showed a high flank wear after the cutting length of
SC
65m, all the coated tools had lower flank wear than the uncoated tools. Especially, the
NU
wear curve of TiVN/TiSiN-HB coated tool slightly increased. This trend seemed to be due to higher hardness as shown in Fig. 9. The TiVN/TiSiN-HB coated tools
MA
possessed the lowest progression of tool wear due to its high wear resistance. Fig. 10 shows the optical microscopic images of uncoated and coated tools after
PT E
D
machining of 7003 aluminum alloys tested after the cutting length of 65m. For the uncoated and the TiSiN coated tools, the main failure mode was adhesion
CE
(build-up-edge formation), as shown by arrows in the figure. The abrasion was intensified on the tool edge of the uncoated tools, even severe adhesive wear occurred
AC
on the surface at the vicinity of the cutting edge. This adhesion failure was due to the strong interaction of the substrate with the workpiece material at high temperature. No obvious adhesive wear and chipping were found on the TiVN and multilayered TiVN/TiSiN. The multilayered TiVN/TiSiN-HB showed a dense and compact structure with TiN and TiVN interlayers, which improved the adhesion strength on the end mills. At the same time, the coating possessed high hardness to resist abrasion. 17
ACCEPTED MANUSCRIPT
The build-up-edge formation reduced, and this results in tool life improvement. The polishing wear of TiVN/TiSiN-HB is beneficial in avoiding the material build-up at the cutting edge. Similar results of polishing wear were also found for the multilayered CrAlN/VN and HfN/VN coatings, which exhibited preferable wear
PT
resistance attributed to interfacial strengthening and the formation of lubricated
RI
vanadium oxide layers between the coating and counter material, and therefore
SC
improving the cutting performance [57, 58]. In this study, the TiVN/TiSiN-HB coated
NU
tools possessed the best cutting performance among the TiVN, TiSiN and multilayered TiVN/TiSiN coatings, and thus provided the longest lifetime of milling
MA
tools. Properly dense multilayered structure of TiVN/TiSiN increased the surface hardness of coated tools, and possessed high wear resistance with low friction, thus
CE
4. Conclusions
PT E
D
minimizing chipping and wear.
AC
In this study, we present a comparative research on structure, mechanical, and tribological properties of TiVN, TiSiN and multilayered TiVN/TiSiN coatings synthesized by cathodic-arc evaporation. The TiVN/TiSiN multilayered coating exhibited the same cubic NaCl-type structure with TiVN and TiSiN coatings. The alternate growth of TiVN and TiSiN in multilayered TiVN/TiSiN coatings resulted in periodic multilayered structure, and the multilayered coatings exhibited high hardness and tribological performance. Both the TiVN/TiSiN deposited at low bias voltage (-30 18
ACCEPTED MANUSCRIPT
V) and high bias voltage (-180 V) had the same average bilayer thickness of 5.2 nm. The TiVN/TiSiN-HB using high bias voltage (-180 V) exhibited dense structure and higher layer thickness ratio of TiVSiN to TiSiN.
PT
The multilayered coatings of TiVN/TiSiN possessed higher hardness than those of individual TiVN and TiSiN coatings. The multilayered TiVN/TiSiN-HB coating
RI
exhibited the highest hardness of 37±0.8 GPa and H3/E⁎2 ratio of 0.46 GPa among the
SC
studied coatings. The lowest wear rate (0.24x10-7 mm3/Nm) was obtained for the
NU
TiVN/TiSiN-HB coated sample due to the highest hardness and lubricious effect.
MA
The TiVN and multilayered TiVN/TiSiN coatings are useful at high speed machining of the high strength Al alloys. An increase of tool lives of the coated end
D
mills was obtained by TiVN/TiSiN-HB, which can be attributed to the good
PT E
tribological performance. Due to the high hardness and low adhesive build-up-edge tendency, the multilayered TiVN/TiSiN-HB coatings may improve the overall
AC
CE
tribological wear resistance and applicability of these coatings in metal machining.
Acknowledgements The funding in part from the Ministry of Science and Technology (Taiwan) under the contract MOST 106-2221-E-150-011 is sincerely appreciated. Besides, the instrument helps from the common lab. for micr/nano sci. and tech. of National Formosa University are sincerely appreciated.
19
ACCEPTED MANUSCRIPT
References [1] E. Santecchia, A.M.S. Hamouda, F. Musharavati, E. Zalnezhad, M. Cabibbo, S.
PT
Spigarelli, Wear resistance investigation of titanium nitride-based coatings, Ceram. Int. 41 (2015) 10349 -10379.
RI
[2] D. Dinesh Kumar, N. Kumar, S. Kalaiselvam, S. Dash, R. Jayavel, Wear resistant
SC
super-hard multilayer transition metal-nitride coatings, Surf. Interfaces 7 (2017)
NU
74–82.
Technol. 258 (2014) 1–16.
MA
[3] Y. X. Wang, S. Zhang, Toward hard yet tough ceramic coatings, Surf. Coat.
D
[4] Y.Y. Chang, H.M. Lai, Wear behavior and cutting performance of CrAlSiN and
PT E
TiAlSiN hard coatings on cemented carbide cutting tools for Ti alloys, Surf. Coat. Technol. 259 (2014)152–158.
CE
[5] S. Hogmark, P. Hedenqvist, Tribological characterization of thin, hard coatings,
AC
Wear 179 (1994) 147-154. [6] D.V. Shtansky, Ph.V. Kiryukhantsev-Korneev, I.A. Bashkova, A.N. Sheveiko, E.A. Levashov, Multicomponent nanostructured films for various tribological applications, Int. J. Refract. Met. Hard Mater. 28 (2010) 32-39. [7] K. Zhang, J. Deng, X. Guo, L. Sun, S. Lei, Study on the adhesion and tribological behavior of PVD TiAlN coatings with a multi-scale textured substrate surface, Int. J. Refract. Met. Hard Mater. 72 (2018) 292-305. 20
ACCEPTED MANUSCRIPT
[8] G. Su, Z. Liu, Wear characteristics of nano TiAlN-coated carbide tools in ultra-high speed machining of AerMet100, Wear 289 (2012) 124-131. [9] Radhika Ramadoss, N. Kumar , R. Pandian, S. Dash, T.R. Ravindran, D. Arivuoli, A.K. Tyagi, Tribological properties and deformation mechanism of TiAlN coating
PT
sliding with various counterbodies, Tribol. Int. 66 (2013) 143-149.
RI
[10] Y.Y. Chang, S.M. Yang, High Temperature oxidation behavior of multicomponent
SC
TiAlSiN coatings, Thin Solid Films 518 (2010) 534-537.
NU
[11] Y. X. Xu, L. Chen, Z. Q. Liu, F. Pei, Y. Du, Improving thermal stability of TiSiN nanocomposite coatings by multilayered epitaxial growth, Surf. Coat. Technol.
MA
321 (2017) 180-185.
[12] Stan Veprek, Maritza J.G. Veprek-Heijman, Industrial applications of superhard
PT E
D
nanocomposite coatings, Surf.Coat.Technol. 202 (2008) 5063-5073. [13] A. Miletić, P. Panjan, B. Škorić, M. Čekada, G.Dražič, J. Kovač, Microstructure
CE
and mechanical properties of nanostructured Ti–Al–Si–N coatings deposited by magnetron sputtering, Surf.Coat.Technol. 241 (2014) 105-111.
AC
[14] S. M. Yang, Y.Y. Chang, D.Y. Lin, D.Y. Wang, W. Wu, Mechanical and tribological properties of multilayered TiSiN/CrN coatings synthesized by a cathodic arc deposition process, Surf.Coat.Technol. 202 (2008) 2176-2181. [15] Y. Yuan, Z. Qin, D.H. Yu, C.Y. Wang, J. Sui, H. Lin, Q. Wang, Relationship of microstructure, mechanical properties and hardened steel cutting performance of TiSiN-based nanocomposite coated tool, J. Manuf. Process. 28 (2017) 399-409. 21
ACCEPTED MANUSCRIPT
[16] Y.H. Cheng, T. Browne, B. Heckerman, E.I. Meletis, Mechanical and tribological properties of nanocomposite TiSiN coatings, Surf.Coat.Technol. 204 (2010) 2123-2129. [17] Y.Y. Chang, S.J. Yang, W. Wu, Y.C. Kuo, J.W. Lee, C.J. Wang, Mechanical
PT
properties of gradient and multilayered TiAlSiN hard coatings, Thin Solid Films,
RI
517/17 (2009) 4934-4937.
SC
[18] Y.Y. Chang, C.M. Cheng, Y.Y. Liou, W. Tillmann, F. Hoffmann, T. Sprute, High
NU
temperature wettability of multicomponent CrAlSiN and TiAlSiN coatings by molten glass, Surf. Coat. Technol. 231 (2013) 24-28.
coatings
sliding
against
MA
[19] J.H. Ouyang, S. Sasaki, Tribo-oxidation of cathodic arc ion-plated (V,Ti)N a
steel
ball
under
both
unlubricated
and
PT E
D
boundary-lubricated conditions, Surf. Coat. Technol. 187 (2004) 343-357. [20] Q. Luo, Temperature dependent friction and wear of magnetron sputtered coating
CE
TiAlN/VN, Wear 271 (2011) 2058-2066. [21] Y. X. Xu, L. Chen, F. Pei, J. L. Yue, Y. Du, Thermal stability and oxidation
AC
resistance of V-alloyed TiAlN coatings, Ceram. Int. 44(2018) 1705-1710. [22] W. Tillmann, T. Sprute, F. Hoffmann, Y.Y. Chang, C.Y. Tsai, Influence of bias voltage on residual stresses and tribological properties of TiAlVN-coatings at elevated temperatures, Surf. Coat. Technol. 231 (2013) 122-125. [23] J. Zechner, O. Kolednik, Fracture resistance of aluminum multilayer composites, Eng Fract. Mech. 110 (2013) 489-500. 22
ACCEPTED MANUSCRIPT
[24] U. Helmersson, S. Todorova, S.A. Barnett, J.E. Sundgren, L.C. Markert, J.E. Greene, Growth of single ‐ crystal TiN/VN strained ‐ layer superlattices with extremely high mechanical hardness, J. Appl. Phys., 62 (1987), pp. 81-87 [25] Y.Y. Chang, W.T. Chiu, J.P. Hung, Mechanical properties and high temperature
RI
evaporation, Surf. Coat. Technol. 303A (2016) 18-24.
PT
oxidation of CrAlSiN/TiVN hard coatings synthesized by cathodic arc
SC
[26] K.N. Andersen, E.J. Bienk, K.O. Schweitz, H. Reitz, J.Chevallier, P.Kringhøj, J.
NU
Bøttiger, Deposition, microstructure and mechanical and tribological properties of magnetron sputtered TiN/TiAlN multilayers, Surf. Coat. Technol. 123 (2000)
MA
219-226.
[27] J. Wang, M.A.P. Yazdi, F. Lomello, A. Billard, A. Kovács, F. Schuster, C. Guet,
PT E
D
T.J. White, F. Sanchette, Z.L. Dong, Influence of microstructures on mechanical properties and tribology behaviors of TiN/TixAl1-xN multilayer coatings, Surf.
CE
Coat. Technol. 320 (2017) 441-446. [28] Y.Y. Chang, S. J. Yang, D.Y. Wang, Structural and mechanical properties of
AC
AlxTi1-xN/CrN coatings synthesized by a cathodic-arc deposition process, Surf. Coat. Technol. 201 (2006) 4209-4214. [29] X. Gu, Z. Zhang, M. Bartosik, P.H. Mayrhofer, H. Duan, Dislocation densities and alternating strain fields in CrN/AlN nanolayers, Thin Solid Films 638 (2017) 189-200. [30] C.T. Guo, D. Lee, P.C. Chen, Deposition of TiSiN coatings by arc ion plating 23
ACCEPTED MANUSCRIPT
process, Appl. Surf. Sci.
254 (2008) 3130-3136.
[31] C.L. Chang, C.T. Lin, P.C. Tsai, W.Y. Ho, D.Y. Wang, Influence of bias voltages on the structure and wear properties of TiSiN coating synthesized by cathodic arc plasma evaporation, Thin Solid Films 516 (2008) 5324-5329.
PT
[32] T. Deeleard, A. Buranawong, A. Choeysuppaket, N. Witit-anun, P. Limsuwan,
RI
Structure and Composition of TiVN Thin Films Deposited by Reactive DC
SC
Magnetron Co-sputtering, Procedia Eng. 32 (2012) 1000-1005.
NU
[33] F. Fernandes, J.C. Oliveira, A. Cavaleiro, Self-lubricating TiSi(V)N thin films deposited by deep oscillation magnetron sputtering (DOMS), Surf. Coat. Technol.
MA
308 (2016) 256-263.
[34] H. Elmkhah, T.F. Zhang, A. Abdollah-zadeh, K.H. Kim, F. Mahboubi, Surface
PT E
D
characteristics for the TiAlN coatings deposited by high power impulse magnetron sputtering technique at the different bias voltages, J Alloys Compd. 688 (2016)
CE
820-827.
[35] Q. Ma, L. Li, Y. Xu, J. Gu, L. Wang, Yi Xu, Effect of bias voltage on TiAlSiN
AC
nanocomposite coatings deposited by HiPIMS, Appl. Surf. Sci. 392 (2017) 826-833.
[36] P. Dubey, G. Martinez, S. Srivastava, R. Chandra, C.V. Ramana, Effect of bias induced microstructure on the mechanical properties of nanocrystalline zirconium tungsten nitride coatings, Surf. Coat. Technol. 313 (2017) 121–128.
24
ACCEPTED MANUSCRIPT
[37] G. Abadias, Stress and preferred orientation in nitride-based PVD coatings, Surf. Coat. Technol. 202 (2008) 2223-2235. [38] A.G. Gómez, A.A.C. Recco, N.B. Lima, L.G. Martinez, A.P.Tschiptschin, R.M. Souza, Residual stresses in titanium nitride thin films obtained with step variation
PT
of substrate bias voltage during deposition, Surf. Coat. Technol. 204 (2010)
RI
3228-3233.
SC
[39] P.C. Wo, P.R. Munroe, Z.F. Zhou, K.Y. Li, Z.H. Xie, Effects of TiN sublayers on
NU
the response of TiSiN nanocomposite coatings to nanoidentation and scratching contacts, Mater. Sci. Eng., A 527 (2010) 4447-4457.
MA
[40] J.C. Oliveira, F. Fernandes, F. Ferreira, A. Cavaleiro, Tailoring the nanostructure of Ti-Si-N thin films by HiPIMS in deep oscillation magnetron sputtering (DOMS)
PT E
D
mode, Surf. Coat. Technol. 264 (2015) 140-149. [41] L. Chen, Y. Du, S.Q. Wang, Ai.J. Wang, H.H. Xu, Mechanical properties and
CE
microstructural evolution of TiN coatings alloyed with Al and Si, Mater. Sci. Eng. A, 502 (2009) 139-143.
AC
[42] Y.Y. Chang, C.J. Wu, Mechanical properties and impact resistance of multilayered TiAlN/ZrN coatings, Surf. Coat. Technol. 231 (2013) 62-66. [43] J.Y. Jao, S. Han, L.S. Chang, C.L. Chang, Y.C. Liu, H. C. Shih, Bias voltage effect on the structure and property of chromium copper–diamond-like carbon multilayer films fabricated by cathodic arc plasma, Appl. Surf. Sci. 256 (2010) 7490-7495. 25
ACCEPTED MANUSCRIPT
[44] S. K. Kim, V. V. Le, Deposition of nanolayered CrN/AlBN thin films by cathodic arc deposition: Influence of cathode arc current and bias voltage on the mechanical properties, Surf. Coat. Technol. 204 (2010) 3941-3946. [45] P.M. Anderson, C. Li, Hall-Petch relations for multilayered materials, Nanostruct.
PT
Mater., 5 (1995) 349-36.
RI
[46] G. Li, Z. Han, J. Tian, J. Xu, M. Gu, Alternating stress field and superhardness
SC
effect in TiN/NbN superlattice films, J. Vac. Sci. Technol. A, 20 (2002) 674-677.
NU
[47] M. P. Deutschmann, P. H. Mayrhofer, K. Chladil, M. Penoy, C. Michotte, C. Mitterer, Effect of wavelength modulation of arc evaporated Ti–Al–N/Ti–Al–V–N
Solid Films 581 (2015) 20-24.
MA
multilayer coatings on microstructure and mechanical/tribological properties, Thin
PT E
D
[48] B.O. Postolnyi, V.M. Beresnev, G. Abadias, O.V. Bondar, A.D. Pogrebnjak, Multilayer design of CrN/MoN protective coatings for enhanced hardness and
CE
toughness, J. Alloys Compd. 725 (2017) 1188-1198. [49] A. Leyland, A. Matthews, On the significance of the H/E ratio in wear control: a
AC
nanocomposite coating approach to optimised tribological behavior, Wear, 246 (2000) 1-11.
[50] Z.T. Wu, Z.B. Qi, B.B. Wei, D.F. Zhang, Z.C. Wang, Understanding hardness evolution of Zr–Si–N nanocomposite coatings via investigating their deformation behaviors, J. Eur. Ceram. Soc. 36 (2016) 3329-3339. [51] J. Guo, H. Wang, F. Meng, X. Liu, F. Huang, Tuning the H/E* ratio and E* of 26
ACCEPTED MANUSCRIPT
AlN coatings by copper addition, Surf. Coat. Technol. 228 (2013) 68-75. [52] J. Kim, J.S. Kyeong, M.H. Ham, A.M. Minor, D.H. Kim, E.S. Park, Development of Mo‐Ni‐Si‐B metallic glass with high thermal stability and H versus E ratios, Mater. Design 98 (2016) 31-40.
RI
loading, Surf. Coat. Technol. 205 (2010) 2687-2695.
PT
[53] A.K. Krella, An approach to evaluate the resistance of hard coatings to shock
SC
[54] W.-D Münz, L.A Donohue, P.Eh Hovsepian, Properties of various large-scale
NU
fabricated TiAlN- and CrN-based superlattice coatings grown by combined cathodic arc–unbalanced magnetron sputter deposition, Surf. Coat. Technol. 125
MA
(2000) 269-277.
[55] F. Fernandes, T. Polcar, A. Cavaleiro, Tribological properties of self-lubricating
PT E
D
TiSiVN coatings at room temperature, Surf. Coat. Technol. 267 (2015) 8-14. [56] P. Panjan, A. Drnovšek, J. Kovač, M. Čekada, M. Panjan, Oxidation processes in
230-237.
CE
vanadium-based single-layer and nanolayer hard coatings, Vacuum 138 (2017)
AC
[57] Y. Wang, J.W. Lee, J.G. Duh, Mechanical strengthening in self-lubricating CrAlN/VN multilayer coatings for improved high-temperature tribological characteristics, Surf. Coat. Technol. 303 (2016) 12-17. [58] J.H. Navarro-Devia, C. Amay, J.C. Caicedo, W. Aperador, Performance evaluation of HSS cutting tool coated with hafnium and vanadium nitride multilayers, by temperature measurement and surface inspection, on machining 27
ACCEPTED MANUSCRIPT
AC
CE
PT E
D
MA
NU
SC
RI
PT
AISI 1020 steel, Surf. Coat. Technol. 332 (2017) 484-493.
28
ACCEPTED MANUSCRIPT
List of figures: Fig. 1. Glancing angle X-ray diffraction spectra of the deposited TiVN, TiSiN and multilayered TiVN/TiSiN-LB and TiVN/TiSiN-HB coatings. Fig. 2. Cross-sectional SEM micrographs of the deposited TiVN, TiSiN and
PT
multilayered TiVN/TiSiN-LB and TiVN/TiSiN-HB coatings.
RI
Fig. 3. HRTEM micrograph of the multilayered TiVN/TiSiN-LB and TiVN/TiSiN-HB
SC
coatings shows the individual TiVN and TiSiN layers.
NU
Fig. 4. SEM micrographs of the Rockwell indentation on the samples coated with TiVN, TiSiN and multilayered TiVN/TiSiN-LB and TiVN/TiSiN-HB.
MA
Fig. 5. Hardness, (a) Young modulus and (b) H3/E⁎2 ratio of the deposited TiVN, TiSiN and multilayered TiVN/TiSiN-LB and TiVN/TiSiN-HB coatings.
PT E
D
Fig. 6. (a) Friction coefficient curves of the TiVN, TiSiN and multilayered TiVN/TiSiN-LB and TiVN/TiSiN-HB coatings. (b) Coefficient of friction
m.
CE
(COF) and the wear rate of the deposited coatings after sliding distance of 600
AC
Fig. 7. SEM image and O mapping of the wear track of TiVN coated samples after sliding distance of 600 m. Fig. 8. Wear track of the TiVN, TiSiN and multilayered TiVN/TiSiN-LB and TiVN/TiSiN-HB coated samples after sliding distance of 600 m. Fig. 9. Progression of average flank wear vs. cutting length of the TiVN, TiSiN and multilayered TiVN/TiSiN-LB and TiVN/TiSiN-HB coated end mills. 29
ACCEPTED MANUSCRIPT
Fig. 10. Optical microscopic images of uncoated and coated tools after machining of
AC
CE
PT E
D
MA
NU
SC
RI
PT
7003 aluminum alloys tested after the cutting length of 65 m.
30
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9
Figure 10
Yin-Yu Chang, Hung Chang, Liang-Jhan Jhao, Chih-Cheng Chuang PII: DOI: Reference:
S0257-8972(18)30158-0 doi:10.1016/j.surfcoat.2018.02.040 SCT 23111
To appear in:
Surface & Coatings Technology
Received date: Revised date: Accepted date:
6 November 2017 17 January 2018 12 February 2018
Please cite this article as: Yin-Yu Chang, Hung Chang, Liang-Jhan Jhao, Chih-Cheng Chuang , Tribological and mechanical properties of multilayered TiVN/TiSiN coatings synthesized by cathodic arc evaporation. The address for the corresponding author was captured as affiliation for all authors. Please check if appropriate. Sct(2017), doi:10.1016/ j.surfcoat.2018.02.040
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.
ACCEPTED MANUSCRIPT Tribological and mechanical properties of multilayered TiVN/TiSiN coatings synthesized by cathodic arc evaporation Yin-Yu Chang1*, Hung Chang1, Liang-Jhan Jhao1, Chih-Cheng Chuang1 1
Department of Mechanical and Computer-Aided Engineering, National Formosa University, Taiwan
Abstract
PT
The flexibility of the physical vapor deposition (PVD) method in obtaining
RI
coatings with a delicate control at a nanometric level provides superior properties.
SC
Among these coatings, transition metal nitride coatings based on Ti, Si, Al and V,
NU
such as TiAlN, TiSiN and TiVN, have been attracting great interest for industrial applications as protective coating materials due to their high hardness, wear resistance
MA
and tribological performance. In this study, TiVN, TiSiN and multilayered TiVN/TiSiN coatings were deposited onto tungsten carbide tools using cathodic-arc
PT E
D
evaporation (CAE) system. During the coating process of TiVN/TiSiN, TiN was deposited as an interlayer to enhance adhesion strength between the coatings and
CE
substrates. The main objective of the present work is to investigate the effect of TiVN on the microstructure, mechanical properties and tribological performance of the
AC
deposited TiVN/TiSiN coatings by regulating the bias voltage during the coating process. The multilayered TiVN/TiSiN coatings exhibited higher hardness of 35~37 GPa, indicating higher resistance against plastic deformation compared to TiVN and TiSiN. The result of ball-on-disc wear tests and end milling tests of 7000 series Al alloys showed that the lowest wear rate and the longest tool life were obtained for the multilayered TiVN/TiSiN coating deposited at high bias voltage of 180 V, which was 1
ACCEPTED MANUSCRIPT
significantly better than that of the monolayered TiSiN.
AC
CE
PT E
D
MA
NU
SC
RI
PT
Keywords: hard coating; TiVN; TiSiN; mechanical; multilayer; tribological
2
ACCEPTED MANUSCRIPT
1. Introduction The superior tribological properties of materials are mainly governed by high hardness, improved resistance to plastic deformation and surface inertness. Hard coatings reduce the tool temperature by reducing the friction between chip and rake
PT
face of a tool. Additionally, low chemical reactivity of coatings with workpiece
RI
materials protects against welding and thus reduces the adhesive wear. The result of
SC
all these effects shows that coated tools can operate at higher cutting speed and higher
NU
feed rate. Thus hard coating expands the safe zone of cutting tools by minimizing the built-up edge (BUE) formation and crater wear. In this aspect, micro- and
MA
nano-structured hard coatings have been widely used as protective tool coatings and considered to be crucial in the production of mechanical parts and tools, owing to
PT E
D
their high hardness, thermal stability and wear resistance properties [1-6]. In early researches, TiSiN and TiAlN have gained much attention as substitutes for traditional
CE
binary nitride coatings with regard to industrial applications involving wear protection, cutting tools and machinery components. Properties of simple TiN can be greatly
AC
enhanced by addition of other elements, such as Al or Si. Incorporation of Al in fcc-TiN structure leads to formation of TiAlN coatings characterized by high hardness (around 32 GPa) and high oxidation resistance (up to 800 °C). This enables TiAlN coatings synthesized by physical vapor deposition (PVD) to be a material with a broad
range
of
applications,
especially
as
cutting
tools
for
machining
difficult-to-machine materials under harsh environments [7-9]. Moreover, the addition 3
ACCEPTED MANUSCRIPT
of Si and Al into TiN to form TiSiN and TiAlSiN results in coatings with superior properties compared to TiN and TiAlN with regard to thermal stability and mechanical performance [10-18]. These multicomponent nitride coatings have been reported to have superior wear resistance because of the formation of stable oxide
PT
layers on the worn surfaces. However, the oxides formed at the tribo-contact area are
RI
not always effective in reducing friction and wear of materials, which depends on
SC
morphology and chemistry of oxides. The addition of vanadium into TiN and TiAlN
NU
to form TiVN and TiAlVN provided improved tribological performance in the increasingly severe working conditions, such as the high working temperatures
MA
through the possible formation of lubricious surface oxides [19-22]. The improvement of tribological performance of protective coatings can be
PT E
D
achieved by increasing hardness and fracture toughness. A possible approach involves the replacement of monolayered coatings by multilayers to meet the above
CE
requirement. Multilayered architecture acts as a crack inhibitor and thereby improves the fracture resistance [23]. Multilayered coatings composed of different layers show
AC
superior mechanical strength, such as hardness and wear resistance, as compared to monolayered coatings due to their specific interfaces. Especially, TiN and TiVN based multilayered coatings such as TiN/VN, TiN/TiAlN and CrAlSiN/TiVN systems have been widely studied, and they exhibit superior mechanical and tribological properties than in the form of a single layer. Such properties in multilayered structure depend mostly on the microstructure of each layer, interfacial adhesion and thickness of each 4
ACCEPTED MANUSCRIPT
layer [2, 24-27]. The nanoscale-multilayered coatings showed that nanoscale strain optimization by multilayers with different periodic bilayer thicknesses, is an effective way to make coating materials possessing good mechanical and tribological properties superior to those of the constituents in the multilayers [28, 29]. In this study, cathodic
PT
arc evaporation (CAE) ion plating system with TiV and TiSi alloy targets was used for
RI
the deposition of TiVN, TiSiN and TiVN/TiSiN multilayered coatings. The
SC
tribological properties and cutting performance of TiVN, TiSiN and TiVN/TiSiN
NU
multilayered coatings were analyzed.
MA
2. Experimental details
TiVN, TiSiN and multilayered TiVN/TiSiN coatings were deposited using a
PT E
D
CAE system (YG-7850, Surfwell Co., Taiwan) on polished tungsten carbide samples (WC-Co, HV ~ 1600) and standard tungsten carbide end mills (diameter= 6 mm, 2
CE
flutes) at temperature of 280-320 °C. Pure Ti, TiV (40 at.% of Ti and 60 at.% of V) and TiSi (80 at.% of Ti and 20 at.% of Si) alloy targets with diameter of 100.5 mm
AC
were used for the deposition. TiV and TiSi alloy targets were arranged on opposite sides of the chamber. This configuration prevented significant intermixing of the metal vapor arriving at the cathodes. The samples were placed on a movable sample holder, which was fixed perpendicular to the target kept at a distance of 170 mm, and the rotation speed was 4 rpm. Before deposition, a combination of rotary and turbomolecular pumps were used to achieve a base pressure of ∼1 × 10−3 Pa in the 5
ACCEPTED MANUSCRIPT
vacuum chamber. Substrates were cleaned again by Ar ion bombardment using a bias voltage of -800 V for 20 min. The cathode current of the targets was 70~80 A to control the composition of the coatings. For the TiVN and TiSiN coatings, Ti and TiN was deposited as interlayers. The total N2 pressure was maintained at 3.2 Pa, and
PT
applied bias voltage was -120 V. For the deposition of multilayered TiVN/TiSiN
RI
coatings, TiN and TiVN were used as the bottom interlayers to improve the adhesion
SC
strength between the coating and substrate interfaces, and then TiVN/TiSiN
NU
multilayers were deposited. The utilization of substrate bias voltage to accelerate the sputtered ions in sputtering plasmas is an effective way to control the properties of
MA
coating. Two kinds of TiVN/TiSiN coatings were prepared using a low bias voltage of -30 V (denoted as TiVN/TiSiN-LB) and a high bias voltage of -180 V (denoted as
PT E
D
TiVN/TiSiN-HB). The deposition time was 50 minutes. The crystallography of TiVN, TiSiN and multilayered TiVN/TiSiN coatings was
CE
characterized by X-ray diffraction (D8 Discover, Bruker Inc.) using Cu Kα radiation (λ = 0.154 nm). The diffractometer was operated at 40 kV and 1 mA and a step size of
AC
0.02° was maintained. It was performed at a low glancing incidence angle of 2o allowing identifying the coating structure. The x-ray beam incidence angle on the thin film sample was fixed while the detector was moved along the goniometer circle in the 2θ range between 30° and 80° to obtain the diffraction profile of reflecting (hkl) lattice planes. The coating morphology and microstructure were investigated by using a JEOL JSM-6700F field emission scanning electron microscope (FESEM) and a 6
ACCEPTED MANUSCRIPT
JEM-ARM200FTH field emission transmission electron microscope (FETEM). Focused ion beam (FIB, SMI3050, Seiko Instruments Inc.) was performed for TEM sample milling. The obtained cross-section thin specimens were finally attached to a copper grid suitable for TEM observation.
PT
The adhesion strength of the coated samples was evaluated using the Rockwell
RI
C indentation (HR-200, Mitutoyo Taiwan Co.) test with an applied load of 150 kg
SC
according to the ISO 26443 standard. The Rockwell indenter was equipped with a
NU
spheroconical diamond tip with a radius of 200 μm and an angle of 120°. The indents were inspected with an optical microscope (100 × magnification). Hardness of the
MA
films were obtained using XP-MTS nano-indentation with a Berkovich indenter, under load-unloading condition, and measured as a function of indenter displacement
PT E
D
using continuous stiffness measurement method. In order to minimize the influence of substrate on the measurement of mechanical properties of the coatings, the maximum
CE
indentation depth was approximately 10% of the coating thickness. A constant Poisson's ratio of ν = 0.25 was assumed for the deposited coatings. On the basis of
AC
these measurements, the force-displacement curve was obtained. From the load-displacement data, hardness can be determined. Five indents were conducted to obtain the average hardness values. The tribological behavior of the coatings was evaluated using a tribometer in ball-on-disc mode (CSM Instruments, Switzerland). A tungsten carbide ball with a diameter of 6.35 mm was used as the sliding counter body. For each measurement, the applied load and sliding speed were kept constant at 5 N 7
ACCEPTED MANUSCRIPT
and 30 mm/s, respectively. In order to meet the harsh environment in tribological sliding, these experiments were carried out in an ambient atmospheric condition without lubricant. The wear track morphology and wear volumes were analyzed and determined using a confocal laser-scanning microscope ((VK-X100, Keyence Inc.).
PT
For the machining experiment, the workpiece material AA7003 Al alloy (tensile
RI
strength= 380 MPa) was machined by the coated end mills (∅8 mm, 2 flutes). The
SC
cutting tests were carried out by dry milling using a 3-axis CNC milling machine (B8,
NU
Takumi Machinery Co., Ltd.). The cutting speed (Vc) was 400 m/min, depth of cut (ap) was 0.5 mm, and feed rate (fz) was 0.013 mm/tooth. Compressed air was
MA
supplied during the cutting experiment. Tool wear was measured using a microscope after a specific machining time period. The wear morphologies of the cutting edge
PT E
D
were also examined with a 3D laser scanning microscope (VK-X100, Keyence Inc.).
3. Results and discussion
CE
3.1 Microstructure characterization
AC
The crystal structures of the TiVN, TiSiN and multilayered TiVN/TiSiN (TiVN/TiSiN-LB and TiVN/TiSiN-HB) coatings examined by glancing X-ray diffraction (XRD) are shown in Fig. 1. All the samples are composed of typical cubic B1-NaCl structures. The diffraction peaks of TiVN were located at 36.72o, 42.96o, 62.38o and 74.70o, which corresponding to (111) (200), (220) and (311) planes. The lattice parameter of the TiVN was 0.421 nm, which was between the values of cubic TiN (0.424 nm, JCPDF file No.: #870629) and VN (0.414 nm, JCPDF file No.: 8
ACCEPTED MANUSCRIPT
#897381). The deposited TiSiN coating had only TiN B1-NaCl crystallite structure with a lattice parameter of 0.426 nm, and no peaks of crystalline Si3N4 were detected. The most important feature is that the XRD patterns exhibit only one group of peaks of fcc structure indicating a single phase solid-solution nitride formation rather than
PT
the co-existence of respective crystalline nitrides [14, 30-33]. The multilayered
RI
TiVN/TiSiN-LB and TiVN/TiSiN-HB coatings also exhibited B1-NaCl crystal
SC
structure. The major peaks corresponding to the (111), (200) and (220) planes for the
NU
NaCl type of crystalline structure were observed. The stabilization of the cubic phase is due to TiVN/TiSiN growth on cubic TiN and TiVN interlayers. In the multilayers,
MA
various growth directions of FCC grains show up, implying the coherent structure formed by successive stack of TiVN and TiSiN. The XRD peaks tended to shift to
PT E
D
lower diffraction angle as the bias voltage increased. Similar results were found in the previous studies [31, 34-36]. The competition in atomic peening, adatom mobility and
CE
resputtering with increasing bias voltage controlled the microstructure of coatings. The atomic peening led to re-arrangement of the lattice atoms and induces stress into
AC
the coating. The intensive ion bombardment induced collisions in adatoms and a higher mobility of adatoms. Such thermally-induced increase in the ad-atom mobility induces growth in those crystallographic directions [36-38]. Fig. 2 showed fractured cross-sectional FESEM images of the TiVN, TiSiN and multilayered TiVN/TiSiN (TiVN/TiSiN-LB and TiVN/TiSiN-HB) coatings. It revealed columnar microstructure of the coating. Columnar gains are oriented in a 9
ACCEPTED MANUSCRIPT
way that the longer axes of the grains are parallel to the growth direction of the coating. The columnar microstructure is typical for the coatings deposited at low gas pressures and low temperatures compared to melting point. Assisted by the EDS at the same time, the deposited TiVN had a TiN interlayer and a transition layer (Ti-rich
PT
TiVN). The deposited TiSiN had a TiN interlayer and a transition layer (Ti-rich
RI
TiSiN). Distinct interfaces can be seen at the boundaries between transition layer and
SC
the top TiSiN layer. No obvious discontinuity in the grain boundary of the associated
NU
columnar grain can be seen. In this TiSiN, addition of Si inhibited the grain growth and induced grain re-nucleation which resulted in compact and dense structure [13, 18,
MA
39-42]. The deposited TiVN/TiSiN-LB and TiVN/TiSiN-HB coatings had a TiN interlayer and 2 transition layers, which were deposited by co-evaporation of Ti, TiV
PT E
D
and TiSi targets in a nitrogen environment. Deposited at a high bias voltage of -180 V, the top TiVN/TiSiN layer of TiVN/TiSiN-HB showed fine dense columnar structures.
CE
The high resolution TEM (HRTEM) images of the TiVN/TiSiN-LB and TiVN/TiSiN-HB multilayered coatings are presented in Fig. 3. The HRTEM
AC
micrograph demonstrated the nanocrystalline structure of the deposited TiVN/TiSiN. The bright-field atomic fringes were visible in all the grains. The lamellar structure can be observed. The white layer is TiSiN, and the black layer is TiVN, respectively. The top layer of the TiVN/TiSiN coating reveals a multilayered structure with stacking of TiVN and TiSiN layers. Measured from TEM observation, the average periodic bilayer thickness (one layer of TiVN and one layer of TiSiN) of 10
ACCEPTED MANUSCRIPT
TiVN/TiSiN-LB deposited at -30 V was about 5.2 nm, and the layer thickness ratio of TiVN to TiSiN is 1.08, which showed the thickness of TiVN and TiSiN was similar. Interfaces between TiVN and TiSiN are coherent. The same crystal structure of TiVN and TiSiN and small mismatch between the lattices showed a good condition for
PT
epitaxial growth. For the TiVN/TiSiN-HB, measured by EDS, the black layer
RI
contained small fraction of Si (~4 at.%). Deposited at high bias voltage of -180 V,
SC
TiSiN and TiVN easily inter-diffused to each other to form composite TiVSiN. The
NU
average periodic bilayer thickness (one layer of TiVSiN and one layer of TiSiN) of TiVN/TiSiN-HB deposited at -180 V was about 5 nm, which showed a little smaller
MA
than the TiVN/TiSiN-LB. The TiVN/TiSiN-HB exhibited a higher layer thickness ratio of TiVSiN to TiSiN of 4.1. The thickness of TiSiN layer decreases to ~0.9 nm
PT E
D
probably because of the re-sputtering effect of TiSiN and the inter-diffusion effect under high bias voltage. Similar results were found in (Cr:Cu)-DLC and CrN/AlBN
CE
multilayered films using CAE at high bias voltage [43, 44]. The result suggested the fundamental nature of ion bombardment during deposition at different bias voltages
AC
of -30 V and -180V, in which the energetic particle impingement of different TiVN and TiSiN played an important role in the evolution of the deposited multilayers.
3.2 Mechanical, tribological and cutting performances TiVN, TiSiN and multilayered TiVN/TiSiN coatings The adhesion strength of all the TiVN, TiSiN and multilayered TiVN/TiSiN 11
ACCEPTED MANUSCRIPT
coated samples were investigated using the Rockwell indentation test, as shown in Fig. 4. Excepted TiSiN, all the other TiVN and multilayered TiVN/TiSiN coatings showed that cone cracks developed beneath the indenter followed by radial cracks around the indentation. The radial cracks without delamination indicated strong adhesive strength
PT
between coating and substrate, and the adhesion strength in this case was evaluated to
RI
class 1. The TiSiN showed that ring cracks and partial delamination were found
SC
around the indentation, and it exhibited poor adhesion strength, which was evaluated
NU
as the criteria of class 2. Fig. 5 shows the measured hardness (H), Young’s modulus (E) and H3/E⁎2 ratio of the TiVN, TiSiN and multilayered TiVN/TiSiN-LB and
MA
TiVN/TiSiN-HB coatings. The hardness of the deposited TiVN, TiSiN coating was 25±0.3 GPa and 34±0.5 GPa, respectively. The Young’s modulus of the deposited
PT E
D
TiSiN was 293 ±16 GPa, and it was similar to that of TiVN (298 ±15 GPa). The multilayered TiVN/TiSiN-LB and TiVN/TiSiN-HB had higher values of Young’s
CE
modulus (305~315 GPa). The results showed that the multilayered coatings of TiVN/TiSiN possessed higher hardness than those of individual TiVN and TiSiN
AC
coatings. The multilayered TiVN/TiSiN-HB coating deposited at high bias voltage of -180 V exhibited the highest hardness of 37±0.8 GPa. As compared to TiVN/TiSiN-LB, the higher hardness of the TiVN/TiSiN-HB is due to the increasing bias voltage in a proper range, leading to effective ion bombardment and resulting in dense structure formed in the TiVN/TiSiN-HB. Similar results were found in the study of TiSiN coatings with different bias voltages [31]. It revealed that the presence of the 12
ACCEPTED MANUSCRIPT
nanolayered structure of the TiVN/TiSiN could increase the hardness based on the interfacial strengthening of epitaxially grown multilayers combining different strengthening mechanisms, such as Hall-Petch and coherency strain relations for multilayered materials [45, 46]. For the TiVN/TiSiN-HB coating deposited at high
PT
bias voltage of -180 V, it was reasonable to assume that the compositional modulation
RI
from layers V rich in TiVSiN to TiSiN, corresponding to different alloying contents in
SC
the formed solid solution, should also contribute to the enhanced hardness [47].
NU
Previous studies also showed that the multilayered coatings, such as TiN/VN,
monolithic coatings [24, 42, 48].
MA
TiAlN/ZrN and CrN/MoN, possessed higher values of hardness than those of
To evaluate mechanical properties of films and to predict protective features of
PT E
D
coatings, the ratios of hardness to elastic modulus could be used. Both the coating hardness and the elastic modulus have been proposed to play crucial roles in
CE
determining the wear and cracking resistances of the hard coatings. Previous studies had shown that this behavior was expressed by the H/E* or H3/E⁎2 ratio, where H and
AC
E⁎ are the hardness and effective modulus of the coating. E⁎ could be further expressed as E* = E/(1-v2), where E is the elastic modulus, and v is the Poisson ratio (~ 0.25) [49, 50]. With higher H and lower E⁎, the plastic deformation is lower. As shown in Fig. 5(b), the H3/E⁎2 ratio of TiVN and TiSiN was 0.16 and 0.39, respectively. The multilayered TiVN/TiSiN-LB coatings exhibited higher H3/E⁎2 ratio (0.41) than that of TiVN and TiSiN. The H3/E⁎2 ratio showed the highest value of 0.46 13
ACCEPTED MANUSCRIPT
GPa for the multilayered TiVN/TiSiN-HB coating. J. Guo et. al. [51] conformed that a high H/E* value was desirable for the triboligical applications. In this study, the high H3/E⁎2 ratio of the multilayered TiVN/TiSiN-HB could be beneficial to enhance the wear resistance [49, 51-53].
PT
Ball-on-disc tribological tests were performed to evaluate the friction and wear
RI
properties of the TiVN, TiSiN and multilayered TiVN/TiSiN coatings. Fig. 6(a) shows
SC
the relationship between the coefficient of friction (COF) and the sliding distances
NU
under dry sliding conditions. All friction curves exhibit running-in and steady state stages. During the running-in, the COF increase with increasing sliding distance, as a
MA
result of the contact stress variations and the coated surface. The coatings showed similar trends in the evolution of friction coefficient from the beginning until the
PT E
D
initial rapid running-in resulting in rapid increase in COF and then a steady-state wear regime. During the run-in stage, the TiSiN showed the highest COF of ~0.78. The
CE
temporary decrease in friction coefficient after the running-in period was more prominent in the multilayered TiVN/TiSiN-HB than for the other coatings. Fig. 6 (b)
AC
shows the COF and the wear rate of coatings tested at room temperature under dry sliding conditions. The highest average COF was obtained for the TiSiN coated sample with values of 0.66. The TiVN/TiSiN-LB coated sample showed lower COF of 0.6 than that of TiSiN. The introducing TiVN into the TiVN/TiSiN-LB in a multilayered structure consisting of TiVN and TiSiN provided a lubrication effect, and lowered the COF to 0.6. W.-D Münz et al. also reported a lower COF when 14
ACCEPTED MANUSCRIPT
testing superlattice TiAlN/VN samples against polycrystalline alumina counterparts at normal load 5N [54]. V addition successfully reduced the wear rate and friction coefficient of TiSiN system. In their study, the tribolayer consisting mostly of vanadium oxides was formed on the surface of TiVN coating. However, the addition
PT
of silicon had detrimental effect on tribolayer formation during the sliding process.
RI
Fig. 7 showed the SEM image and O mapping of the wear track of TiVN coated
SC
samples after sliding distance of 600 m. The formation of thin tribolayers comprising
NU
lubricious phases such as titanium oxides and vanadium oxides was probably responsible for the lowering COF as compared to TiSiN. The lowest COF was
MA
obtained for the TiVN/TiSiN-HB coating with a value of 0.32, while the COF of TiVN coating was 0.42 due to the low hardness of 25±0.3 GPa. From the result of
PT E
D
microstructure characterization, the TiVN/TiSiN-HB exhibits a higher layer thickness ratio of TiVSiN to TiSiN of 4.1. This TiVSiN in the TiVN/TiSiN-HB may lead to the
CE
lowest COF of 0.32. A similar result showing the surface V-O, Ti-O and Si-O lubricious oxides on the sliding contact zone of TiVSiN can be found in the previous
AC
study by F. Fernandes et. al. [55]. The highest average COF and wear rate were found for the TiSiN coated sample. The TiVN/TiSiN-LB coated sample showed lower COF of 0.6 and lower wear of 4.4x10-7 mm3/Nm than that of TiSiN. The lowest wear rate (0.24x10-7 mm3/Nm) was obtained for the TiVN/TiSiN-HB coated sample due to the highest hardness and lubricious effect of TiVN. It revealed that the wear resistance of TiVN/TiSiN-HB 15
ACCEPTED MANUSCRIPT
coating was the best among the TiVN, TiSiN and multilayered TiVN/TiSiN coatings. Therefore, TiVN/TiSiN-HB provided improved tribological behavior through the complementary properties of surface oxide formation resisting adhesion wear and high hardness against abrasive wear. From the tribological point of view, P. Panjan et
PT
al. [56] also showed that the CrN/CrVN/VN multilayered hard coatings provided a
RI
high potential for application as a wear-resistant and self-lubricating coating. It
SC
suggested that the bulk diffusion of the vanadium through such layer was hindered
NU
and thus the only possible diffusion paths were growth defects as well as voids between the columns. As compared to TiSiN, vanadium-containing coatings exhibited
MA
a different wear mechanism. Polishing wear occurred in TiVN and multilayered TiVN/TiSiN-HB coatings as demonstrated by smooth worn surfaces, as show in Fig. 8.
PT E
D
The wear track of TiVN and multilayered TiVN/TiSiN-HB coatings showed scratches parallel to the relative sliding movement suggesting polishing wear as the dominant
CE
wear mechanism. As compared to TiVN/TiSiN-HB, the lower hardness of TiVN resulted in the higher wear rate. In addition to the highest hardness of
AC
TiVN/TiSiN-HB resisting the abrasion wear, the wear track of TiVN/TiSiN-HB is smooth and free of longitudinal micro-grooves. Therefore, the multilayered TiVN/TiSiN-HB possessed the lowest wear rate. In this study, TiVN, TiSiN and multilayered TiVN/TiSiN were deposited on the tungsten carbide cutting tools, and the cutting tests were conducted on 7003 aluminum alloy by dry milling at high cutting speed of 400 m/min. The 16
ACCEPTED MANUSCRIPT
challenge in cutting such aluminum alloy materials is the pronounced adhesion of the workpiece material to the cutting edge leading to early blunting when the edge is completely covered. Fig. 9 shows the relationship between cutting length and average flank wear obtained with different tools. Except the multilayered TiVN/TiSiN-HB, the
PT
average flank wear increased rapidly with increasing cutting length before the cutting
RI
length of 13 m. The uncoated tool showed a high flank wear after the cutting length of
SC
65m, all the coated tools had lower flank wear than the uncoated tools. Especially, the
NU
wear curve of TiVN/TiSiN-HB coated tool slightly increased. This trend seemed to be due to higher hardness as shown in Fig. 9. The TiVN/TiSiN-HB coated tools
MA
possessed the lowest progression of tool wear due to its high wear resistance. Fig. 10 shows the optical microscopic images of uncoated and coated tools after
PT E
D
machining of 7003 aluminum alloys tested after the cutting length of 65m. For the uncoated and the TiSiN coated tools, the main failure mode was adhesion
CE
(build-up-edge formation), as shown by arrows in the figure. The abrasion was intensified on the tool edge of the uncoated tools, even severe adhesive wear occurred
AC
on the surface at the vicinity of the cutting edge. This adhesion failure was due to the strong interaction of the substrate with the workpiece material at high temperature. No obvious adhesive wear and chipping were found on the TiVN and multilayered TiVN/TiSiN. The multilayered TiVN/TiSiN-HB showed a dense and compact structure with TiN and TiVN interlayers, which improved the adhesion strength on the end mills. At the same time, the coating possessed high hardness to resist abrasion. 17
ACCEPTED MANUSCRIPT
The build-up-edge formation reduced, and this results in tool life improvement. The polishing wear of TiVN/TiSiN-HB is beneficial in avoiding the material build-up at the cutting edge. Similar results of polishing wear were also found for the multilayered CrAlN/VN and HfN/VN coatings, which exhibited preferable wear
PT
resistance attributed to interfacial strengthening and the formation of lubricated
RI
vanadium oxide layers between the coating and counter material, and therefore
SC
improving the cutting performance [57, 58]. In this study, the TiVN/TiSiN-HB coated
NU
tools possessed the best cutting performance among the TiVN, TiSiN and multilayered TiVN/TiSiN coatings, and thus provided the longest lifetime of milling
MA
tools. Properly dense multilayered structure of TiVN/TiSiN increased the surface hardness of coated tools, and possessed high wear resistance with low friction, thus
CE
4. Conclusions
PT E
D
minimizing chipping and wear.
AC
In this study, we present a comparative research on structure, mechanical, and tribological properties of TiVN, TiSiN and multilayered TiVN/TiSiN coatings synthesized by cathodic-arc evaporation. The TiVN/TiSiN multilayered coating exhibited the same cubic NaCl-type structure with TiVN and TiSiN coatings. The alternate growth of TiVN and TiSiN in multilayered TiVN/TiSiN coatings resulted in periodic multilayered structure, and the multilayered coatings exhibited high hardness and tribological performance. Both the TiVN/TiSiN deposited at low bias voltage (-30 18
ACCEPTED MANUSCRIPT
V) and high bias voltage (-180 V) had the same average bilayer thickness of 5.2 nm. The TiVN/TiSiN-HB using high bias voltage (-180 V) exhibited dense structure and higher layer thickness ratio of TiVSiN to TiSiN.
PT
The multilayered coatings of TiVN/TiSiN possessed higher hardness than those of individual TiVN and TiSiN coatings. The multilayered TiVN/TiSiN-HB coating
RI
exhibited the highest hardness of 37±0.8 GPa and H3/E⁎2 ratio of 0.46 GPa among the
SC
studied coatings. The lowest wear rate (0.24x10-7 mm3/Nm) was obtained for the
NU
TiVN/TiSiN-HB coated sample due to the highest hardness and lubricious effect.
MA
The TiVN and multilayered TiVN/TiSiN coatings are useful at high speed machining of the high strength Al alloys. An increase of tool lives of the coated end
D
mills was obtained by TiVN/TiSiN-HB, which can be attributed to the good
PT E
tribological performance. Due to the high hardness and low adhesive build-up-edge tendency, the multilayered TiVN/TiSiN-HB coatings may improve the overall
AC
CE
tribological wear resistance and applicability of these coatings in metal machining.
Acknowledgements The funding in part from the Ministry of Science and Technology (Taiwan) under the contract MOST 106-2221-E-150-011 is sincerely appreciated. Besides, the instrument helps from the common lab. for micr/nano sci. and tech. of National Formosa University are sincerely appreciated.
19
ACCEPTED MANUSCRIPT
References [1] E. Santecchia, A.M.S. Hamouda, F. Musharavati, E. Zalnezhad, M. Cabibbo, S.
PT
Spigarelli, Wear resistance investigation of titanium nitride-based coatings, Ceram. Int. 41 (2015) 10349 -10379.
RI
[2] D. Dinesh Kumar, N. Kumar, S. Kalaiselvam, S. Dash, R. Jayavel, Wear resistant
SC
super-hard multilayer transition metal-nitride coatings, Surf. Interfaces 7 (2017)
NU
74–82.
Technol. 258 (2014) 1–16.
MA
[3] Y. X. Wang, S. Zhang, Toward hard yet tough ceramic coatings, Surf. Coat.
D
[4] Y.Y. Chang, H.M. Lai, Wear behavior and cutting performance of CrAlSiN and
PT E
TiAlSiN hard coatings on cemented carbide cutting tools for Ti alloys, Surf. Coat. Technol. 259 (2014)152–158.
CE
[5] S. Hogmark, P. Hedenqvist, Tribological characterization of thin, hard coatings,
AC
Wear 179 (1994) 147-154. [6] D.V. Shtansky, Ph.V. Kiryukhantsev-Korneev, I.A. Bashkova, A.N. Sheveiko, E.A. Levashov, Multicomponent nanostructured films for various tribological applications, Int. J. Refract. Met. Hard Mater. 28 (2010) 32-39. [7] K. Zhang, J. Deng, X. Guo, L. Sun, S. Lei, Study on the adhesion and tribological behavior of PVD TiAlN coatings with a multi-scale textured substrate surface, Int. J. Refract. Met. Hard Mater. 72 (2018) 292-305. 20
ACCEPTED MANUSCRIPT
[8] G. Su, Z. Liu, Wear characteristics of nano TiAlN-coated carbide tools in ultra-high speed machining of AerMet100, Wear 289 (2012) 124-131. [9] Radhika Ramadoss, N. Kumar , R. Pandian, S. Dash, T.R. Ravindran, D. Arivuoli, A.K. Tyagi, Tribological properties and deformation mechanism of TiAlN coating
PT
sliding with various counterbodies, Tribol. Int. 66 (2013) 143-149.
RI
[10] Y.Y. Chang, S.M. Yang, High Temperature oxidation behavior of multicomponent
SC
TiAlSiN coatings, Thin Solid Films 518 (2010) 534-537.
NU
[11] Y. X. Xu, L. Chen, Z. Q. Liu, F. Pei, Y. Du, Improving thermal stability of TiSiN nanocomposite coatings by multilayered epitaxial growth, Surf. Coat. Technol.
MA
321 (2017) 180-185.
[12] Stan Veprek, Maritza J.G. Veprek-Heijman, Industrial applications of superhard
PT E
D
nanocomposite coatings, Surf.Coat.Technol. 202 (2008) 5063-5073. [13] A. Miletić, P. Panjan, B. Škorić, M. Čekada, G.Dražič, J. Kovač, Microstructure
CE
and mechanical properties of nanostructured Ti–Al–Si–N coatings deposited by magnetron sputtering, Surf.Coat.Technol. 241 (2014) 105-111.
AC
[14] S. M. Yang, Y.Y. Chang, D.Y. Lin, D.Y. Wang, W. Wu, Mechanical and tribological properties of multilayered TiSiN/CrN coatings synthesized by a cathodic arc deposition process, Surf.Coat.Technol. 202 (2008) 2176-2181. [15] Y. Yuan, Z. Qin, D.H. Yu, C.Y. Wang, J. Sui, H. Lin, Q. Wang, Relationship of microstructure, mechanical properties and hardened steel cutting performance of TiSiN-based nanocomposite coated tool, J. Manuf. Process. 28 (2017) 399-409. 21
ACCEPTED MANUSCRIPT
[16] Y.H. Cheng, T. Browne, B. Heckerman, E.I. Meletis, Mechanical and tribological properties of nanocomposite TiSiN coatings, Surf.Coat.Technol. 204 (2010) 2123-2129. [17] Y.Y. Chang, S.J. Yang, W. Wu, Y.C. Kuo, J.W. Lee, C.J. Wang, Mechanical
PT
properties of gradient and multilayered TiAlSiN hard coatings, Thin Solid Films,
RI
517/17 (2009) 4934-4937.
SC
[18] Y.Y. Chang, C.M. Cheng, Y.Y. Liou, W. Tillmann, F. Hoffmann, T. Sprute, High
NU
temperature wettability of multicomponent CrAlSiN and TiAlSiN coatings by molten glass, Surf. Coat. Technol. 231 (2013) 24-28.
coatings
sliding
against
MA
[19] J.H. Ouyang, S. Sasaki, Tribo-oxidation of cathodic arc ion-plated (V,Ti)N a
steel
ball
under
both
unlubricated
and
PT E
D
boundary-lubricated conditions, Surf. Coat. Technol. 187 (2004) 343-357. [20] Q. Luo, Temperature dependent friction and wear of magnetron sputtered coating
CE
TiAlN/VN, Wear 271 (2011) 2058-2066. [21] Y. X. Xu, L. Chen, F. Pei, J. L. Yue, Y. Du, Thermal stability and oxidation
AC
resistance of V-alloyed TiAlN coatings, Ceram. Int. 44(2018) 1705-1710. [22] W. Tillmann, T. Sprute, F. Hoffmann, Y.Y. Chang, C.Y. Tsai, Influence of bias voltage on residual stresses and tribological properties of TiAlVN-coatings at elevated temperatures, Surf. Coat. Technol. 231 (2013) 122-125. [23] J. Zechner, O. Kolednik, Fracture resistance of aluminum multilayer composites, Eng Fract. Mech. 110 (2013) 489-500. 22
ACCEPTED MANUSCRIPT
[24] U. Helmersson, S. Todorova, S.A. Barnett, J.E. Sundgren, L.C. Markert, J.E. Greene, Growth of single ‐ crystal TiN/VN strained ‐ layer superlattices with extremely high mechanical hardness, J. Appl. Phys., 62 (1987), pp. 81-87 [25] Y.Y. Chang, W.T. Chiu, J.P. Hung, Mechanical properties and high temperature
RI
evaporation, Surf. Coat. Technol. 303A (2016) 18-24.
PT
oxidation of CrAlSiN/TiVN hard coatings synthesized by cathodic arc
SC
[26] K.N. Andersen, E.J. Bienk, K.O. Schweitz, H. Reitz, J.Chevallier, P.Kringhøj, J.
NU
Bøttiger, Deposition, microstructure and mechanical and tribological properties of magnetron sputtered TiN/TiAlN multilayers, Surf. Coat. Technol. 123 (2000)
MA
219-226.
[27] J. Wang, M.A.P. Yazdi, F. Lomello, A. Billard, A. Kovács, F. Schuster, C. Guet,
PT E
D
T.J. White, F. Sanchette, Z.L. Dong, Influence of microstructures on mechanical properties and tribology behaviors of TiN/TixAl1-xN multilayer coatings, Surf.
CE
Coat. Technol. 320 (2017) 441-446. [28] Y.Y. Chang, S. J. Yang, D.Y. Wang, Structural and mechanical properties of
AC
AlxTi1-xN/CrN coatings synthesized by a cathodic-arc deposition process, Surf. Coat. Technol. 201 (2006) 4209-4214. [29] X. Gu, Z. Zhang, M. Bartosik, P.H. Mayrhofer, H. Duan, Dislocation densities and alternating strain fields in CrN/AlN nanolayers, Thin Solid Films 638 (2017) 189-200. [30] C.T. Guo, D. Lee, P.C. Chen, Deposition of TiSiN coatings by arc ion plating 23
ACCEPTED MANUSCRIPT
process, Appl. Surf. Sci.
254 (2008) 3130-3136.
[31] C.L. Chang, C.T. Lin, P.C. Tsai, W.Y. Ho, D.Y. Wang, Influence of bias voltages on the structure and wear properties of TiSiN coating synthesized by cathodic arc plasma evaporation, Thin Solid Films 516 (2008) 5324-5329.
PT
[32] T. Deeleard, A. Buranawong, A. Choeysuppaket, N. Witit-anun, P. Limsuwan,
RI
Structure and Composition of TiVN Thin Films Deposited by Reactive DC
SC
Magnetron Co-sputtering, Procedia Eng. 32 (2012) 1000-1005.
NU
[33] F. Fernandes, J.C. Oliveira, A. Cavaleiro, Self-lubricating TiSi(V)N thin films deposited by deep oscillation magnetron sputtering (DOMS), Surf. Coat. Technol.
MA
308 (2016) 256-263.
[34] H. Elmkhah, T.F. Zhang, A. Abdollah-zadeh, K.H. Kim, F. Mahboubi, Surface
PT E
D
characteristics for the TiAlN coatings deposited by high power impulse magnetron sputtering technique at the different bias voltages, J Alloys Compd. 688 (2016)
CE
820-827.
[35] Q. Ma, L. Li, Y. Xu, J. Gu, L. Wang, Yi Xu, Effect of bias voltage on TiAlSiN
AC
nanocomposite coatings deposited by HiPIMS, Appl. Surf. Sci. 392 (2017) 826-833.
[36] P. Dubey, G. Martinez, S. Srivastava, R. Chandra, C.V. Ramana, Effect of bias induced microstructure on the mechanical properties of nanocrystalline zirconium tungsten nitride coatings, Surf. Coat. Technol. 313 (2017) 121–128.
24
ACCEPTED MANUSCRIPT
[37] G. Abadias, Stress and preferred orientation in nitride-based PVD coatings, Surf. Coat. Technol. 202 (2008) 2223-2235. [38] A.G. Gómez, A.A.C. Recco, N.B. Lima, L.G. Martinez, A.P.Tschiptschin, R.M. Souza, Residual stresses in titanium nitride thin films obtained with step variation
PT
of substrate bias voltage during deposition, Surf. Coat. Technol. 204 (2010)
RI
3228-3233.
SC
[39] P.C. Wo, P.R. Munroe, Z.F. Zhou, K.Y. Li, Z.H. Xie, Effects of TiN sublayers on
NU
the response of TiSiN nanocomposite coatings to nanoidentation and scratching contacts, Mater. Sci. Eng., A 527 (2010) 4447-4457.
MA
[40] J.C. Oliveira, F. Fernandes, F. Ferreira, A. Cavaleiro, Tailoring the nanostructure of Ti-Si-N thin films by HiPIMS in deep oscillation magnetron sputtering (DOMS)
PT E
D
mode, Surf. Coat. Technol. 264 (2015) 140-149. [41] L. Chen, Y. Du, S.Q. Wang, Ai.J. Wang, H.H. Xu, Mechanical properties and
CE
microstructural evolution of TiN coatings alloyed with Al and Si, Mater. Sci. Eng. A, 502 (2009) 139-143.
AC
[42] Y.Y. Chang, C.J. Wu, Mechanical properties and impact resistance of multilayered TiAlN/ZrN coatings, Surf. Coat. Technol. 231 (2013) 62-66. [43] J.Y. Jao, S. Han, L.S. Chang, C.L. Chang, Y.C. Liu, H. C. Shih, Bias voltage effect on the structure and property of chromium copper–diamond-like carbon multilayer films fabricated by cathodic arc plasma, Appl. Surf. Sci. 256 (2010) 7490-7495. 25
ACCEPTED MANUSCRIPT
[44] S. K. Kim, V. V. Le, Deposition of nanolayered CrN/AlBN thin films by cathodic arc deposition: Influence of cathode arc current and bias voltage on the mechanical properties, Surf. Coat. Technol. 204 (2010) 3941-3946. [45] P.M. Anderson, C. Li, Hall-Petch relations for multilayered materials, Nanostruct.
PT
Mater., 5 (1995) 349-36.
RI
[46] G. Li, Z. Han, J. Tian, J. Xu, M. Gu, Alternating stress field and superhardness
SC
effect in TiN/NbN superlattice films, J. Vac. Sci. Technol. A, 20 (2002) 674-677.
NU
[47] M. P. Deutschmann, P. H. Mayrhofer, K. Chladil, M. Penoy, C. Michotte, C. Mitterer, Effect of wavelength modulation of arc evaporated Ti–Al–N/Ti–Al–V–N
Solid Films 581 (2015) 20-24.
MA
multilayer coatings on microstructure and mechanical/tribological properties, Thin
PT E
D
[48] B.O. Postolnyi, V.M. Beresnev, G. Abadias, O.V. Bondar, A.D. Pogrebnjak, Multilayer design of CrN/MoN protective coatings for enhanced hardness and
CE
toughness, J. Alloys Compd. 725 (2017) 1188-1198. [49] A. Leyland, A. Matthews, On the significance of the H/E ratio in wear control: a
AC
nanocomposite coating approach to optimised tribological behavior, Wear, 246 (2000) 1-11.
[50] Z.T. Wu, Z.B. Qi, B.B. Wei, D.F. Zhang, Z.C. Wang, Understanding hardness evolution of Zr–Si–N nanocomposite coatings via investigating their deformation behaviors, J. Eur. Ceram. Soc. 36 (2016) 3329-3339. [51] J. Guo, H. Wang, F. Meng, X. Liu, F. Huang, Tuning the H/E* ratio and E* of 26
ACCEPTED MANUSCRIPT
AlN coatings by copper addition, Surf. Coat. Technol. 228 (2013) 68-75. [52] J. Kim, J.S. Kyeong, M.H. Ham, A.M. Minor, D.H. Kim, E.S. Park, Development of Mo‐Ni‐Si‐B metallic glass with high thermal stability and H versus E ratios, Mater. Design 98 (2016) 31-40.
RI
loading, Surf. Coat. Technol. 205 (2010) 2687-2695.
PT
[53] A.K. Krella, An approach to evaluate the resistance of hard coatings to shock
SC
[54] W.-D Münz, L.A Donohue, P.Eh Hovsepian, Properties of various large-scale
NU
fabricated TiAlN- and CrN-based superlattice coatings grown by combined cathodic arc–unbalanced magnetron sputter deposition, Surf. Coat. Technol. 125
MA
(2000) 269-277.
[55] F. Fernandes, T. Polcar, A. Cavaleiro, Tribological properties of self-lubricating
PT E
D
TiSiVN coatings at room temperature, Surf. Coat. Technol. 267 (2015) 8-14. [56] P. Panjan, A. Drnovšek, J. Kovač, M. Čekada, M. Panjan, Oxidation processes in
230-237.
CE
vanadium-based single-layer and nanolayer hard coatings, Vacuum 138 (2017)
AC
[57] Y. Wang, J.W. Lee, J.G. Duh, Mechanical strengthening in self-lubricating CrAlN/VN multilayer coatings for improved high-temperature tribological characteristics, Surf. Coat. Technol. 303 (2016) 12-17. [58] J.H. Navarro-Devia, C. Amay, J.C. Caicedo, W. Aperador, Performance evaluation of HSS cutting tool coated with hafnium and vanadium nitride multilayers, by temperature measurement and surface inspection, on machining 27
ACCEPTED MANUSCRIPT
AC
CE
PT E
D
MA
NU
SC
RI
PT
AISI 1020 steel, Surf. Coat. Technol. 332 (2017) 484-493.
28
ACCEPTED MANUSCRIPT
List of figures: Fig. 1. Glancing angle X-ray diffraction spectra of the deposited TiVN, TiSiN and multilayered TiVN/TiSiN-LB and TiVN/TiSiN-HB coatings. Fig. 2. Cross-sectional SEM micrographs of the deposited TiVN, TiSiN and
PT
multilayered TiVN/TiSiN-LB and TiVN/TiSiN-HB coatings.
RI
Fig. 3. HRTEM micrograph of the multilayered TiVN/TiSiN-LB and TiVN/TiSiN-HB
SC
coatings shows the individual TiVN and TiSiN layers.
NU
Fig. 4. SEM micrographs of the Rockwell indentation on the samples coated with TiVN, TiSiN and multilayered TiVN/TiSiN-LB and TiVN/TiSiN-HB.
MA
Fig. 5. Hardness, (a) Young modulus and (b) H3/E⁎2 ratio of the deposited TiVN, TiSiN and multilayered TiVN/TiSiN-LB and TiVN/TiSiN-HB coatings.
PT E
D
Fig. 6. (a) Friction coefficient curves of the TiVN, TiSiN and multilayered TiVN/TiSiN-LB and TiVN/TiSiN-HB coatings. (b) Coefficient of friction
m.
CE
(COF) and the wear rate of the deposited coatings after sliding distance of 600
AC
Fig. 7. SEM image and O mapping of the wear track of TiVN coated samples after sliding distance of 600 m. Fig. 8. Wear track of the TiVN, TiSiN and multilayered TiVN/TiSiN-LB and TiVN/TiSiN-HB coated samples after sliding distance of 600 m. Fig. 9. Progression of average flank wear vs. cutting length of the TiVN, TiSiN and multilayered TiVN/TiSiN-LB and TiVN/TiSiN-HB coated end mills. 29
ACCEPTED MANUSCRIPT
Fig. 10. Optical microscopic images of uncoated and coated tools after machining of
AC
CE
PT E
D
MA
NU
SC
RI
PT
7003 aluminum alloys tested after the cutting length of 65 m.
30
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9
Figure 10