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Microstructural and mechanical properties of Si-ion implanted TiN coatings
Surface & Coatings Technology 228 (2013) S292–S295
Contents lists available at SciVerse ScienceDirect
Surface & Coatings Technology journal homepage: www.elsevier.com/locate/surfcoat
Microstructural and mechanical properties of Si-ion implanted TiN coatings Hua Qin, Ye Tao ⁎, Bin Deng School of Materials Science and Engineering, Beihang University, Beijing 100191, China
a r t i c l e
i n f o
Available online 5 June 2012 Keywords: TiN coatings Si ion implantation Nanohardness GIXRD XPS
a b s t r a c t Hard coatings such as CrN, TiN prepared by physical vapor deposition (PVD) have been successfully exploited for wear and corrosion protection, but the defect may adversely affect their properties. Ion implantation as an effective technology can enhance the properties of coatings through modifying the composition and microstructure of coating surface. In this paper, metal vapor vacuum arc (MEVVA) ion source was used to implant silicon ion into TiN coatings with dose of 1 × 1017 ions/cm2 and 5 × 1016 ions/cm2 and the implantation energy was 40 keV. The synchrotron radiation grazing incidence X-ray diffraction (GIXRD) was used to analyze the microstructure and residual stress of the Si-implanted TiN coatings. The calculation of crystal spacing, lattice constant of Si-ion implanted TiN coatings was made by the XRD data analysis software Jade. X-ray photoelectron spectroscopy (XPS) was employed to investigate the profile of the chemical composition. Nanoindenter tested the nanohardness of Si-implanted TiN coatings. The results revealed that the grain size decreased, the nanohardness of Si-ion implanted TiN coatings changed remarkably, but the excessive ion implantation may reduce nanohardness of samples for the heavy irradiation damage. The plastic deformation energy of the coatings increased. New microcrystalline phases were formed which have been proved by XPS. Crown Copyright © 2012 Published by Elsevier B.V. All rights reserved.
1. Introduction Ion implantation is an excellent technology in modifying surface properties of materials [1,2]. A new type of metal arc ion source, namely metal vapor vacuum arc (MEVVA) [3,4], has been used in plasma ion implantation. This technique has been used to modify surface properties, for corrosion resistance [5], tribological [6] and semiconductor applications. In recent years, much research has been done on the effects of ion implantation into hard-coatings and obtained many useful results. Atsushi Mitsuo and Kazutaka Kanda [7] researched friction and wear properties of carbon-ion implanted titanium nitride films and found that the carbon ion implantation reduced the friction coefficient of the TiN films against stainless steel balls, and also the wear volume of steel ball. K.P. Purushotham and L.P. Ward [8] researched the effect of MEVVA ion implantation of Zr on the corrosion behavior of PVD TiN coatings and found that ion implantation resulted in an increase in the coating's corrosion resistance. Jerzy Narojczyk and Zbigniew Werner [9] researched wear resistance of TiN coatings implanted with Al and N ions and found a noticeable increase in the nanohardness of TiN coatings. Recent research focused on the influence of Si content and growth condition on the microstructural and mechanical properties of Ti–Si– N nanocomposite coatings and it found that the nanocomposite
⁎ Corresponding author. Tel.: + 86 1082317115; fax: + 86 1082317125. E-mail address: [email protected] (Y. Tao).
coatings could improve mechanical properties in comparison with TiN deposited under the same condition [10–12]. However, with the increase of the content of Si in coating, the electrical conductivity of coating dropped dramatically, even to zero. However, the ion implantation provided us a new way to implant high dose of Si and control the dose flexibly. This paper works on the properties of Si-implanted TiN coatings, such as nanohardness, microcrystalline structure, implanted atom concentration distribution, wear behavior, and element chemical state. 2. Material and methods Cemented carbide (WC–TiC–Co) was selected as substrate (15 mm × 15 mm × 4 mm) for test. The substrates were ultrasonically degreased, then cleaned by isopropyl alcohol before deposition. All the coatings with a thickness of 1 μm were deposited by the magnetic filtered cathodic arc plating system. After TiN deposition, the samples were moved to another vacuum chamber for silicon ion implantation using the MEVVA ion implantation, varied with different doses: 5 × 10 16 ions/cm 2 and 1 × 10 17 ions/cm 2. The ion energy of the Si implantation was settled as 40 keV. Crystallographic orientation and structure of the coating were analyzed by the synchrotron radiation grazing incidence X-ray diffraction (GIXRD) supplied by Institute of High Energy Physics Chinese Academy of Sciences. Diffraction measurements were performed with a high
0257-8972/$ – see front matter. Crown Copyright © 2012 Published by Elsevier B.V. All rights reserved. doi:10.1016/j.surfcoat.2012.05.119
H. Qin et al. / Surface & Coatings Technology 228 (2013) S292–S295
S293
resolution instrument using Cu Kα radiation of wavelength 1.54478 Å at an incident angle of 0.5°. The data was later analyzed by MDI Jade software. The compositional depth profile and the chemical bonding state of silicon ion implantation TiN coating were measured by the X-ray photoelectron spectroscopy (XPS). XPS measurement was performed using a monochromatized Al Kα radiation from an Al anode operated at 200 W. All XPS spectra were calibrated using the Au 4f7/2 peak at 84 eV. Curve fitting was performed using the Gaussian Lorentzian sum function after a Shirley background subtraction. The hardness of the processed samples was measured using a nanoindenter manufactured by MTS.
3. Results and discussion 3.1. Results of nanoindenter The program of SRIM2008 (TRIM calculation) was chosen to calculate the ion implantation depth. In this simulation process, the energy of implantation was equal to the charge state of Si ions multiplied by accelerating voltage. The parameters of the simulation process were as follows: the energy of implantation: 56 keV (1.4 × 40 keV, the charge state of Si ions: + 1.4, the accelerating voltage: 40 keV). The injection angle was 0°, and the projective range we calculated was 76.5 nm. The indentation depth was close to the ratio Rp, so an error of hardness value was essentially high due to the dimensional effect. Although the value of nanohardness of implanted coatings wasn't absolutely correct, it could be reasonable to reflect the change of nanohardness of the coatings with the test approach that will be discussed later. Nanoindenter was used to investigate the nanohardness of the implanted layer on top of TiN coatings varied with different ion doses. We used the Continuous Stiffness Measurements (CSM) to obtain the load–displacement curve, from which the hardness and Young's modulus were calculated. For each sample, we tested nanohardness in five different places of the coatings. Fig. 1 showed the averaged results based on five times repetitive tests, and Fig. 2 showed the averaged results of five repetitive measurements within 100 nm. In Fig. 1, sample 1, sample 2, and sample 3 reached the micro hardness peak at around 30 nm, 60 nm, and 100 nm, from the surface of coating respectively. The micro hardness peak was 30 GPa, 44 GPa, and 38 GPa. It can be seen in sample 2 that the micro hardness dropped rapidly to 27 GPa at 120 nm while that of sample 3 decreased slowly to 27 GPa at 300 nm from the surface.
In Fig. 2, each point was obtained by averaging the results of five repetitive measurements. The micro hardness of the surface increased from 27.18 GPa to 39.85 GPa after Si ion implantation. But with more ion doses implanted, the micro hardness dropped from 39.85 GPa to 33.27 GPa. It reflects that Si ion implantation modifies the surface layer of TiN coatings, thereby enhancing the micro hardness dramatically improves the wear resistance, which also indicates that Si dose exists in an optimum range to obtain the highest micro hardness. Excessive Si ion implantation may cause the irradiation damage of TiN coating. From the experimental results, it can be seen that Si ion implantation is certainly beneficial for the improvement of micro hardness. The dose dependence of the hardness indicates that the great improvement in the surface properties of TiN coatings could be obtained at doses around 5 × 10 16 ions/cm2. The hardened surface due to Si ion implantation is mainly contributed by the ion‐irradiated very‐nearsurface region; it could be supposed that besides the contribution from the implanted Si ions. Which form the interstitial decorating dislocations or hard Si compound such as Si3N4. The new Si compound will be proved by the latter XPS. However, as seen in the figures, this effect is not linearly proportional to the ion dose. For the case of high-dose Si ion-implanted sample, it is believed that it is because of the heavy irradiation damage. It can be seen in Fig. 3, Young's modulus of sample 3 enhanced from 350 GPa to 650 GPa at near surface. Furthermore, sample 3
Fig. 1. The nanohardness curve of samples.
Fig. 3. The Young's modulus curve of samples.
Fig. 2. The nanohardness of Si-implanted TiN coatings with various implanting ion doses.
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Fig. 4. Load–depth hysteresis loops.
Fig. 6. Relation of dosage with compressive residual stress.
could keep stable modulus than sample 2. It indicates that implanting large doses of Si ion could improve the modulus of TiN coatings. As shown in Fig. 4, the maximum penetration depth is approximately 1000 nm and the maximum load was set at 3 mN. It indicates that the ability of plastic deformation of sample 2 is better than that of sample 3 and sample 1. The curve also shows that the indentation depth was lower for sample 2 than for the others under the same load, which suggested hardening of the coatings.
The residual stress of coatings could be roughly calculated by the following formula:
3.2. GIXRD test The measurements were performed with Cu Kα radiation at an incidence angle of 0.5°. Diffraction patterns are shown in Fig. 5. XRD measurement at a grazing incidence angle of 0.5°was performed to investigate microstructural changes in the near-surface region. In contrast to the standard TiN coating PDF file 6‐642, sample 1 shows the preferred orientation of the (200) planes of TiN coatings. After the Si implantation in the TiN coating, all GIXRD patterns measured from implanted TiN were found to be similar to that of the non-implanted one. According to Fig. 5, the peaks of sample 2 became broader, indicating that crystal structure and residual stresses were developed in the implantation region by silicon ion implantation. The size of crystallites could be calculated using Scherrer formula. However, we can't determine if the new phase, which will be proved in the XPS analysis later, was formed in the implanted layer.
Fig. 5. GIXRD pattern of (a) the TiN coating, (b) Si-implanted TiN coating (5×1016 ions/cm2) and (c)Si-implanted TiN coating (1×1017 ions/cm2).
σ ¼ −ðE=2νÞε ¼ −ðE=2νÞ½ðdn −d0 Þ=d0 : Where E is Young's modulus, ν is Poisson's ratio (ν = 0.22), ε is coating's strain, dn is the interplanar spacing corresponding to the XRD, d0 is the interplanar spacing corresponding to the PDF profile. We use residual stress of (200) planes and σ/σ0 to show the trend. The results are shown in Fig. 6. Since all the samples' residual stress are compressive, indicating that the stress form doesn't change after implantation. But the value of compressive stress becomes smaller, sample 2's equivalent to 80% of unimplanted one's and sample 3's equivalent to the 90% of uniimplanted one's. Compared to Fig. 2, it may indicate that the smaller the compressive stress in the coating, the higher the nanohardness of the coating. According to the M. Bielawski's research [13] the correlation between TiN coating hardness and residual stress level could not be established. High coating hardness typically indicates high residual stress. 3.3. XPS analysis XPS analysis results are shown in Figs. 7, 8 and 9. Si is observed at the top of the surface layer as shown in Fig. 8. Fig. 9 illustrates Si 2p XPS signal detected from Si-implanted TiN at a dose of 1 × 1017 ions/cm 2, it can
Fig. 7. XPS scan for unimplanted.
H. Qin et al. / Surface & Coatings Technology 228 (2013) S292–S295
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leads to the formation of Si3N4 in the implanted zone, the formation of SiO2 may be caused by oxidation after TiN films moved out of the vacuum chamber. It shows that highly energetic silicon ion implantation can induce surface interatomic breaking and bonding. Therefore, high ion energy and dose can enhance the surface nanohardness of the TiN coating by forming silicide and interstitial solid solution within the implanted matrix. 4. Conclusions This work has explored the mechanical and microstructural properties of TiN coatings following the MEVVA plasma ion implantation of Si ions at different ion doses. The results are summarized as follows:
Fig. 8. XPS pattern of sample 3 (1 × 1017 ions/cm2).
(1) The nanohardness of all coatings increased dramatically after Si-implantation in TiN coatings by MEVVA treatment. But the excessive ion implantation may reduce nanohardness of samples for the heavy irradiation damage. (2) GIXRD indicates that the preferred orientation of the (200) planes of TiN coatings is made by MFCAP, and the formation of crystallites with a fine size after silicon ion implantation. (3) XPS shows the microstructural changes of the implanted layer, formation of Si3N4 within the implantation matrix of the TiN coatings.
Acknowledgments The GIXRD test was supported by the Institute of High Energy Physics Chinese Academy of Sciences. References
Fig. 9. XPS-Si 2p spectra of Si-implanted TiN coatings with various implanting ion doses.
be found that the Si 2p spectrum can be de-convoluted into two component peaks at 102.1 eV which was identified to correspond to Si3N4 and another one at 103 eV to SiO2. The result indicates that Si-implantation
[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11]
J. Ishikawa, H. Tsuji, Surf. Coat. Technol. 203 (2009) 2351. V.I. Lavrentiev, A.D. Pogrebnjak, Surf. Coat. Technol. 99 (1-2) (1998) 24. T.H. Zhang, H.X. Zhang, Surf. Coat. Technol. 128–129 (2000) 1. T.H. zhang, X.Y. Wang, Surf. Coat. Technol. 83 (1996) 280. Y. Sugizaki, T. Yasunaga, H. Tomari, Surf. Coat. Technol. 83 (1996) 167. R.R. Manory, S. Mollica, L. Ward, Surf. Coat. Technol. 155 (2002) 136. A. Mitsuo, K. Kanda, T. Aizawa, Surf. Coat. Technol. 128–129 (2000) 440. K.P. Purushotham, L.P. Ward, N. Brack, Corros. Sci. 50 (2008) 8. J. Narojczyk, Z. Werner, Vacuum 81 (2007) 1275. P. Zhang, Z. Cai, Surf. Coat. Technol. 201 (2007) 6819. D.V. Shtansky, I.V. Lyasotsky, N.B. D'yakonova, Surf. Coat. Technol. 182 (2004) 204. [12] P.J. Martin, A. Bendavid, J.M. Cairney, Surf. Coat. Technol. 200 (2005) 2228. [13] M. Bielawski, Surf. Coat. Technol. 200 (2006) 3987.
Contents lists available at SciVerse ScienceDirect
Surface & Coatings Technology journal homepage: www.elsevier.com/locate/surfcoat
Microstructural and mechanical properties of Si-ion implanted TiN coatings Hua Qin, Ye Tao ⁎, Bin Deng School of Materials Science and Engineering, Beihang University, Beijing 100191, China
a r t i c l e
i n f o
Available online 5 June 2012 Keywords: TiN coatings Si ion implantation Nanohardness GIXRD XPS
a b s t r a c t Hard coatings such as CrN, TiN prepared by physical vapor deposition (PVD) have been successfully exploited for wear and corrosion protection, but the defect may adversely affect their properties. Ion implantation as an effective technology can enhance the properties of coatings through modifying the composition and microstructure of coating surface. In this paper, metal vapor vacuum arc (MEVVA) ion source was used to implant silicon ion into TiN coatings with dose of 1 × 1017 ions/cm2 and 5 × 1016 ions/cm2 and the implantation energy was 40 keV. The synchrotron radiation grazing incidence X-ray diffraction (GIXRD) was used to analyze the microstructure and residual stress of the Si-implanted TiN coatings. The calculation of crystal spacing, lattice constant of Si-ion implanted TiN coatings was made by the XRD data analysis software Jade. X-ray photoelectron spectroscopy (XPS) was employed to investigate the profile of the chemical composition. Nanoindenter tested the nanohardness of Si-implanted TiN coatings. The results revealed that the grain size decreased, the nanohardness of Si-ion implanted TiN coatings changed remarkably, but the excessive ion implantation may reduce nanohardness of samples for the heavy irradiation damage. The plastic deformation energy of the coatings increased. New microcrystalline phases were formed which have been proved by XPS. Crown Copyright © 2012 Published by Elsevier B.V. All rights reserved.
1. Introduction Ion implantation is an excellent technology in modifying surface properties of materials [1,2]. A new type of metal arc ion source, namely metal vapor vacuum arc (MEVVA) [3,4], has been used in plasma ion implantation. This technique has been used to modify surface properties, for corrosion resistance [5], tribological [6] and semiconductor applications. In recent years, much research has been done on the effects of ion implantation into hard-coatings and obtained many useful results. Atsushi Mitsuo and Kazutaka Kanda [7] researched friction and wear properties of carbon-ion implanted titanium nitride films and found that the carbon ion implantation reduced the friction coefficient of the TiN films against stainless steel balls, and also the wear volume of steel ball. K.P. Purushotham and L.P. Ward [8] researched the effect of MEVVA ion implantation of Zr on the corrosion behavior of PVD TiN coatings and found that ion implantation resulted in an increase in the coating's corrosion resistance. Jerzy Narojczyk and Zbigniew Werner [9] researched wear resistance of TiN coatings implanted with Al and N ions and found a noticeable increase in the nanohardness of TiN coatings. Recent research focused on the influence of Si content and growth condition on the microstructural and mechanical properties of Ti–Si– N nanocomposite coatings and it found that the nanocomposite
⁎ Corresponding author. Tel.: + 86 1082317115; fax: + 86 1082317125. E-mail address: [email protected] (Y. Tao).
coatings could improve mechanical properties in comparison with TiN deposited under the same condition [10–12]. However, with the increase of the content of Si in coating, the electrical conductivity of coating dropped dramatically, even to zero. However, the ion implantation provided us a new way to implant high dose of Si and control the dose flexibly. This paper works on the properties of Si-implanted TiN coatings, such as nanohardness, microcrystalline structure, implanted atom concentration distribution, wear behavior, and element chemical state. 2. Material and methods Cemented carbide (WC–TiC–Co) was selected as substrate (15 mm × 15 mm × 4 mm) for test. The substrates were ultrasonically degreased, then cleaned by isopropyl alcohol before deposition. All the coatings with a thickness of 1 μm were deposited by the magnetic filtered cathodic arc plating system. After TiN deposition, the samples were moved to another vacuum chamber for silicon ion implantation using the MEVVA ion implantation, varied with different doses: 5 × 10 16 ions/cm 2 and 1 × 10 17 ions/cm 2. The ion energy of the Si implantation was settled as 40 keV. Crystallographic orientation and structure of the coating were analyzed by the synchrotron radiation grazing incidence X-ray diffraction (GIXRD) supplied by Institute of High Energy Physics Chinese Academy of Sciences. Diffraction measurements were performed with a high
0257-8972/$ – see front matter. Crown Copyright © 2012 Published by Elsevier B.V. All rights reserved. doi:10.1016/j.surfcoat.2012.05.119
H. Qin et al. / Surface & Coatings Technology 228 (2013) S292–S295
S293
resolution instrument using Cu Kα radiation of wavelength 1.54478 Å at an incident angle of 0.5°. The data was later analyzed by MDI Jade software. The compositional depth profile and the chemical bonding state of silicon ion implantation TiN coating were measured by the X-ray photoelectron spectroscopy (XPS). XPS measurement was performed using a monochromatized Al Kα radiation from an Al anode operated at 200 W. All XPS spectra were calibrated using the Au 4f7/2 peak at 84 eV. Curve fitting was performed using the Gaussian Lorentzian sum function after a Shirley background subtraction. The hardness of the processed samples was measured using a nanoindenter manufactured by MTS.
3. Results and discussion 3.1. Results of nanoindenter The program of SRIM2008 (TRIM calculation) was chosen to calculate the ion implantation depth. In this simulation process, the energy of implantation was equal to the charge state of Si ions multiplied by accelerating voltage. The parameters of the simulation process were as follows: the energy of implantation: 56 keV (1.4 × 40 keV, the charge state of Si ions: + 1.4, the accelerating voltage: 40 keV). The injection angle was 0°, and the projective range we calculated was 76.5 nm. The indentation depth was close to the ratio Rp, so an error of hardness value was essentially high due to the dimensional effect. Although the value of nanohardness of implanted coatings wasn't absolutely correct, it could be reasonable to reflect the change of nanohardness of the coatings with the test approach that will be discussed later. Nanoindenter was used to investigate the nanohardness of the implanted layer on top of TiN coatings varied with different ion doses. We used the Continuous Stiffness Measurements (CSM) to obtain the load–displacement curve, from which the hardness and Young's modulus were calculated. For each sample, we tested nanohardness in five different places of the coatings. Fig. 1 showed the averaged results based on five times repetitive tests, and Fig. 2 showed the averaged results of five repetitive measurements within 100 nm. In Fig. 1, sample 1, sample 2, and sample 3 reached the micro hardness peak at around 30 nm, 60 nm, and 100 nm, from the surface of coating respectively. The micro hardness peak was 30 GPa, 44 GPa, and 38 GPa. It can be seen in sample 2 that the micro hardness dropped rapidly to 27 GPa at 120 nm while that of sample 3 decreased slowly to 27 GPa at 300 nm from the surface.
In Fig. 2, each point was obtained by averaging the results of five repetitive measurements. The micro hardness of the surface increased from 27.18 GPa to 39.85 GPa after Si ion implantation. But with more ion doses implanted, the micro hardness dropped from 39.85 GPa to 33.27 GPa. It reflects that Si ion implantation modifies the surface layer of TiN coatings, thereby enhancing the micro hardness dramatically improves the wear resistance, which also indicates that Si dose exists in an optimum range to obtain the highest micro hardness. Excessive Si ion implantation may cause the irradiation damage of TiN coating. From the experimental results, it can be seen that Si ion implantation is certainly beneficial for the improvement of micro hardness. The dose dependence of the hardness indicates that the great improvement in the surface properties of TiN coatings could be obtained at doses around 5 × 10 16 ions/cm2. The hardened surface due to Si ion implantation is mainly contributed by the ion‐irradiated very‐nearsurface region; it could be supposed that besides the contribution from the implanted Si ions. Which form the interstitial decorating dislocations or hard Si compound such as Si3N4. The new Si compound will be proved by the latter XPS. However, as seen in the figures, this effect is not linearly proportional to the ion dose. For the case of high-dose Si ion-implanted sample, it is believed that it is because of the heavy irradiation damage. It can be seen in Fig. 3, Young's modulus of sample 3 enhanced from 350 GPa to 650 GPa at near surface. Furthermore, sample 3
Fig. 1. The nanohardness curve of samples.
Fig. 3. The Young's modulus curve of samples.
Fig. 2. The nanohardness of Si-implanted TiN coatings with various implanting ion doses.
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Fig. 4. Load–depth hysteresis loops.
Fig. 6. Relation of dosage with compressive residual stress.
could keep stable modulus than sample 2. It indicates that implanting large doses of Si ion could improve the modulus of TiN coatings. As shown in Fig. 4, the maximum penetration depth is approximately 1000 nm and the maximum load was set at 3 mN. It indicates that the ability of plastic deformation of sample 2 is better than that of sample 3 and sample 1. The curve also shows that the indentation depth was lower for sample 2 than for the others under the same load, which suggested hardening of the coatings.
The residual stress of coatings could be roughly calculated by the following formula:
3.2. GIXRD test The measurements were performed with Cu Kα radiation at an incidence angle of 0.5°. Diffraction patterns are shown in Fig. 5. XRD measurement at a grazing incidence angle of 0.5°was performed to investigate microstructural changes in the near-surface region. In contrast to the standard TiN coating PDF file 6‐642, sample 1 shows the preferred orientation of the (200) planes of TiN coatings. After the Si implantation in the TiN coating, all GIXRD patterns measured from implanted TiN were found to be similar to that of the non-implanted one. According to Fig. 5, the peaks of sample 2 became broader, indicating that crystal structure and residual stresses were developed in the implantation region by silicon ion implantation. The size of crystallites could be calculated using Scherrer formula. However, we can't determine if the new phase, which will be proved in the XPS analysis later, was formed in the implanted layer.
Fig. 5. GIXRD pattern of (a) the TiN coating, (b) Si-implanted TiN coating (5×1016 ions/cm2) and (c)Si-implanted TiN coating (1×1017 ions/cm2).
σ ¼ −ðE=2νÞε ¼ −ðE=2νÞ½ðdn −d0 Þ=d0 : Where E is Young's modulus, ν is Poisson's ratio (ν = 0.22), ε is coating's strain, dn is the interplanar spacing corresponding to the XRD, d0 is the interplanar spacing corresponding to the PDF profile. We use residual stress of (200) planes and σ/σ0 to show the trend. The results are shown in Fig. 6. Since all the samples' residual stress are compressive, indicating that the stress form doesn't change after implantation. But the value of compressive stress becomes smaller, sample 2's equivalent to 80% of unimplanted one's and sample 3's equivalent to the 90% of uniimplanted one's. Compared to Fig. 2, it may indicate that the smaller the compressive stress in the coating, the higher the nanohardness of the coating. According to the M. Bielawski's research [13] the correlation between TiN coating hardness and residual stress level could not be established. High coating hardness typically indicates high residual stress. 3.3. XPS analysis XPS analysis results are shown in Figs. 7, 8 and 9. Si is observed at the top of the surface layer as shown in Fig. 8. Fig. 9 illustrates Si 2p XPS signal detected from Si-implanted TiN at a dose of 1 × 1017 ions/cm 2, it can
Fig. 7. XPS scan for unimplanted.
H. Qin et al. / Surface & Coatings Technology 228 (2013) S292–S295
S295
leads to the formation of Si3N4 in the implanted zone, the formation of SiO2 may be caused by oxidation after TiN films moved out of the vacuum chamber. It shows that highly energetic silicon ion implantation can induce surface interatomic breaking and bonding. Therefore, high ion energy and dose can enhance the surface nanohardness of the TiN coating by forming silicide and interstitial solid solution within the implanted matrix. 4. Conclusions This work has explored the mechanical and microstructural properties of TiN coatings following the MEVVA plasma ion implantation of Si ions at different ion doses. The results are summarized as follows:
Fig. 8. XPS pattern of sample 3 (1 × 1017 ions/cm2).
(1) The nanohardness of all coatings increased dramatically after Si-implantation in TiN coatings by MEVVA treatment. But the excessive ion implantation may reduce nanohardness of samples for the heavy irradiation damage. (2) GIXRD indicates that the preferred orientation of the (200) planes of TiN coatings is made by MFCAP, and the formation of crystallites with a fine size after silicon ion implantation. (3) XPS shows the microstructural changes of the implanted layer, formation of Si3N4 within the implantation matrix of the TiN coatings.
Acknowledgments The GIXRD test was supported by the Institute of High Energy Physics Chinese Academy of Sciences. References
Fig. 9. XPS-Si 2p spectra of Si-implanted TiN coatings with various implanting ion doses.
be found that the Si 2p spectrum can be de-convoluted into two component peaks at 102.1 eV which was identified to correspond to Si3N4 and another one at 103 eV to SiO2. The result indicates that Si-implantation
[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11]
J. Ishikawa, H. Tsuji, Surf. Coat. Technol. 203 (2009) 2351. V.I. Lavrentiev, A.D. Pogrebnjak, Surf. Coat. Technol. 99 (1-2) (1998) 24. T.H. Zhang, H.X. Zhang, Surf. Coat. Technol. 128–129 (2000) 1. T.H. zhang, X.Y. Wang, Surf. Coat. Technol. 83 (1996) 280. Y. Sugizaki, T. Yasunaga, H. Tomari, Surf. Coat. Technol. 83 (1996) 167. R.R. Manory, S. Mollica, L. Ward, Surf. Coat. Technol. 155 (2002) 136. A. Mitsuo, K. Kanda, T. Aizawa, Surf. Coat. Technol. 128–129 (2000) 440. K.P. Purushotham, L.P. Ward, N. Brack, Corros. Sci. 50 (2008) 8. J. Narojczyk, Z. Werner, Vacuum 81 (2007) 1275. P. Zhang, Z. Cai, Surf. Coat. Technol. 201 (2007) 6819. D.V. Shtansky, I.V. Lyasotsky, N.B. D'yakonova, Surf. Coat. Technol. 182 (2004) 204. [12] P.J. Martin, A. Bendavid, J.M. Cairney, Surf. Coat. Technol. 200 (2005) 2228. [13] M. Bielawski, Surf. Coat. Technol. 200 (2006) 3987.