- Email: [email protected]
Study on the effect of the interlayer on the adhesion of 400 μm thick film
Nuclear Instruments and Methods in Physics Research B 121( 1997) 2 12-2
15 Beam interactions with Materials&Atoms
ELSEVIER
Study on the effect of the interlayer on the adhesion of 400 pm thick film Y. Murakami
*,N. Kuratani, S. Nishiyama, 0. Imai, K. Ogata
R&D Division, N&sin Electric Co.. Ltd., 47, Umrzu-Tukuse-rho, Ukyo-ku, Kyoto 615, Jupun
Abstract We have studied on the effect of the interlayers on the adhesion of 400 p,rn thick Ni-TiN gradient films. In order to improve the adhesion of the Ni-TiN films, the interlayer films are formed at the interfaces between the thick films and tungsten carbide substrates (WC-Co). The interlayers have the Si-Ni multilayer structures and are prepared by ion beam and vapor deposition (IVD) method. The Si interlayers are prepared at various internal stresses on tungsten carbide substrates and the Ni interlayers also are prepared at various internal stresses on the Si interlayers. The 400 pm thick films are formed by cathodic arc ion-plating method on the Si-Ni interlayers. As a result, it seems that it is possible to improve the adhesion of the thick films by decreasing internal stress mismatch among the lower layers of the thick films, upper layers of interlayers and lower layers of interlayers.
7
1. Introduction
Thick films Recently, coating films are increasingly used to improve the performance and lifetime of components in tribological applications. It is also said that adhesion is one of the key determinants of coating performance. The various methods for improvement in adhesion of the films, such as substrate surface cleaning, ion mixing at the interface and the formation of the interlayer, have been studied [l]. We have tried to improve the adhesion of the films which have 400 p,rn thickness by the formation of the interlayers. An increase of the film thickness tends to decrease the adhesion of the films. The internal stresses in the films are regarded as one of the factors in decrease of the adhesion of the films [2]. It is thought that there are two ways to design the interlayers for high adhesion of the films. One is to design the internal stresses in the interlayers which lead to the stress relaxation. However, in the case that the thickness of the films is several hundred times larger than that of the interlayers, stress relaxation of the thick films by interlayers could be hardly expected. Therefore, we have studied the other way, which is to design the internal stresses in the interlayers in order not to cause the internal stress mismatch. The schematic diagram of the interlayers for the thick films on the tungsten carbide substrates is shown in Fig. 1.
* Corresponding author. Fax: + 81-75-882-4120; email: [email protected].
I VD method
c
Fig. I. The schematic diagram of the thick films on the Si-Ni interlayers on the tungsten carbide substrate.
The thick films are formed by cathodic arc ion-plating method and have gradient structures which consist of Ni and TIN. The thick films have high hardness and high toughness [3]. The interlayers require the good adhesion for the tungsten carbide substrates and the Ni-TiN gradient films. The interlayers have the Si-Ni multilayer structures. The Si layers in the interlayers are used for good adhesion of tungsten carbide substrates. The Ni layers in the interlayers are used for good adhesion of the Ni-TiN gradient films. The interlayers are prepared by ion beam and vapor deposition (IVD) method. In this paper, we report on the effect of the interlayers on the adhesion of the 400 km thick films in terms of the internal stress matching.
0168-583X/97/$17.00 Copyright 0 1997 Elsevier Science B.V. All rights reserved PII SO168-583X(96)00399-0
Y. Murakami et al./Nucl.
Instr. and Meth. in Phys. Res. B 121 (1997) 212-215
213
2. Experimental The equipment used for the interlayer preparation was an IVD system, detail of which have been described elsewhere 141. The Si films were prepared by evaporation of silicon and simultaneous irradiation with argon ions on the tungsten carbide substrates (WC-Co). lhe energy of ion bombardment was changed at 0.5, 2.0 and 10.0 keV. The transport ratios of silicon atoms to argon ions, Si/Ar, to the substrates were constant at 7.5. The Si film thickness was changed from 0 to 0.2 m. After the Si films deposition, the Ni films were also prepared by evaporation of nickel and simultaneous irradiation with argon ions. The energy of argon ion bombardment was changed at 0.5, 2.0 and 10.0 keV. The transport ratios, Ni/Ar, were kept at 10. The thickness of Ni films was kept at 1 km. The substrates were kept at low temperature during deposition by water cooling system. After the samples were fractured with a hammer, the cross sections of the samples were examined by scanning electron microscopy GEM) to confirm whether the films peeled from the substrates or not. The internal stresses in the films were measured by the displacements of the Si wafers as substrates after deposition.
3. Results and discussion In the case of the interlayers of which Si films were prepared 0.05 p,rn and 0.10 km with 10.0 keV ion irradiation and the Ni films with 10.0 keV, (Si : 0.05 km, 10.0
Fig. 2. The cross section of the thick films after hammer test in the case of Si films 0.05 km of 10.0 keV and Ni films of 10.0 keV.
keV/Ni: 10.0 keV) and (Si: 0.1 pm, 10.0 keV/Ni: 10.0 keV), the 400 pm thick films could be formed. After hammering, the exfoliation could not be observed in these films as shown in Fig. 2. In the case of the interlayers consisting of only Ni films (without Si films), the 400 pm thick films could not be prepared. The exfoliation faces were analyzed by Auger electron spectroscopy (AES). Fig. 3 shows the AES spectra of the exfoliation face of the substrate side in the case of the Ni interlayers prepared at the energy of 10.0 keV. In this figure, the peaks of tungsten (W), which is the element of substrates, are observed. Therefore, this sample peeled off between the Ni films in the interlayers and the tungsten carbide substrates. It seems that the interlayers need Si
Ni
1000 KINETIC ENERGY (eV) Fig. 3. The AES spectrum of the exfoliation face in the case of the only Ni films of 10.0 keV in interlayer. III. FILM FORMATION
Y. Murakami
214
0.0 ~,‘//I”“, 0 1
i
,I/, 3
1
et al./Nucl.
~
1
~
4
j’
6
7
layers
which
-1.5
“-
I”/”
8
$
10
~
!
0.05
0.00
have good adhesion
and internal
for the tungsten
carbide substrates. In the case of the other Si film conditions and/or Ni film conditions of the interlayers, the thick films also peeled off just after the 400 pm or less deposition. From these results, it seems that the adhesion of the thick films depends strongly on the conditions of the Si-Ni interlayers. The effect of the stress conditions in the interlayers on the adhesion of the thick films is studied in terms of stress matching. Fig. 4 shows the relation between the film thickness and the internal stress in the case of the Ni films by cathodic arc ion-plating (C-AIP), which correspond to
I
j 0, 10
0. 15
0.20
W
0 5 keV 0
2.0 keV
A
IO 0 keV
Fig. 5. The relationship between the Si tilm thickness and internal stresses at various ion energies.
the lower layer of thick films. The internal stresses are constant about 0.6 GPa in tensile stress from 2 km to 10 pm. The thinner C-AIP Ni films, the larger the internal stress as tensile. Therefore, it appears that the near-interface layer in the Ni-TiN thick film is in the state of the large tensile stress. By our previous studies, Ni films prepared with 0.5, 2.0 and 10.0 keV argon ion irradiation, where transport ratios Ni/Ar = 10, were 0.4 GPa in compression, 0.44 GPa in tension and 0.90 GPa in tension. respectively [5]. The
4000
500
1000
KINETIC ENERGY Fig. 6. The AES spectrum of the exfoliation
i 0.25
FILM THICKNESS(Dm)
FILM THICKNESS(,um)
Fig. 4. The relationship between the film thickness stresses in the lower Ni layer of the thick films.
lower
Instr. and Meth. in Phys. Res. B 121 (1997) 212-215
1500
2000
(eV)
face in the case of Si films 0.1 Frn of 10.0 keV and Ni films of 10.0 keV.
Y. Murukrrmi
et ul./Nucl.
Instr. und Mrth.
magnitude of the internal stresses in Ni interlayers with 10.0 keV is the nearest magnitude of the internal stresses in the Ni lower layers of the thick films. Therefore, it seems that the Ni films with 10.0 keV have the improvement effect in adhesion of the thick films because of the good stress matching. In order to study the effect of the Si films conditions on the adhesion of thick films, the internal stresses in Si films were also investigated. The relationship between the Si film thickness and internal stresses at various ion energies is shown in Fig. 5. The internal stresses in the Si films with 0.5 keV and 2.0 keV are only compressive stresses. On the other hand, the internal stresses in the Si films with 10.0 keV are changed from compressive stresses to tensile stresses with decreasing of the film thickness. It has become clear that the Si films also have tensile stresses in the case of the 400 Frn which could be formed. Fig. 6 shows the exfoliation face after rhe thick films deposition in the case of the magnitude of the internal stresses in Si films that are different from those in Ni films. This interlayer consists of the 0.1 pm Si film of 2.0 keV nncl the Ni film of 10.0 keV. In this figure, it appears that the sample peeled off between Si and Ni in interlayer, as the peaks of Ni and Si are observed from this exfoliation place of the sample. It is thought that the difference of the internal stresses in each film causes the peeling off between the interfaces. From these results, it is thought that it is possible to improve the adhesion of the thick films by decreasing internal stress mismatch among the lower layers of the thick films. as well as upper and lower layers of interlayers.
in Phy.1. Ra.
B IZI
215
119971212-215
4. Conclusions We have studied the effect of the interlayers on the adhesion of 400 pm thick films. As a result, it seems that it is possible to improve the adhesion of the thick films by decreasing internal stress mismatch among the lower layers of the thick films, upper layers of interlayers and lower layers of interlayers.
Acknowledgements This work was conducted in the frame of the program on Advanced Chemical Processing Technology, consigned to ACTA from NEDO, which is carried out under the Industrial Science and Technology Frontier Program enforced by the Agency of Industrial Science and Technol-
ogy.
References [I]
J.E.E.Baglin.
[2] S.G.Croll,
Nucl. Instr. and Meth. B 65 (1992)
J. Coat. Technol. 52 (1980)
[3] A.Nakayama.
T.Yoshioka
and T.Nomura,
cation Technologies, eds. T.S.Sudarshan, and K.Kamata [4] K.Ogata,
(The Institute of Materials,
Y.Andoh
119.
35. in: Surface ModifiK.lshizaki.
M.Takata
1994) p. 3 15.
and Kamijo, Nucl. Instr. and Meth. B 33
( 1988) 685. [5] N.Kuratani,
O.Imai,
Coat. Technol. 66
A.Ebe, S.Nishiyama
(I 994)
and K.Ogata.
Surf.
3 IO.
III. FILM
FORMATlON
15 Beam interactions with Materials&Atoms
ELSEVIER
Study on the effect of the interlayer on the adhesion of 400 pm thick film Y. Murakami
*,N. Kuratani, S. Nishiyama, 0. Imai, K. Ogata
R&D Division, N&sin Electric Co.. Ltd., 47, Umrzu-Tukuse-rho, Ukyo-ku, Kyoto 615, Jupun
Abstract We have studied on the effect of the interlayers on the adhesion of 400 p,rn thick Ni-TiN gradient films. In order to improve the adhesion of the Ni-TiN films, the interlayer films are formed at the interfaces between the thick films and tungsten carbide substrates (WC-Co). The interlayers have the Si-Ni multilayer structures and are prepared by ion beam and vapor deposition (IVD) method. The Si interlayers are prepared at various internal stresses on tungsten carbide substrates and the Ni interlayers also are prepared at various internal stresses on the Si interlayers. The 400 pm thick films are formed by cathodic arc ion-plating method on the Si-Ni interlayers. As a result, it seems that it is possible to improve the adhesion of the thick films by decreasing internal stress mismatch among the lower layers of the thick films, upper layers of interlayers and lower layers of interlayers.
7
1. Introduction
Thick films Recently, coating films are increasingly used to improve the performance and lifetime of components in tribological applications. It is also said that adhesion is one of the key determinants of coating performance. The various methods for improvement in adhesion of the films, such as substrate surface cleaning, ion mixing at the interface and the formation of the interlayer, have been studied [l]. We have tried to improve the adhesion of the films which have 400 p,rn thickness by the formation of the interlayers. An increase of the film thickness tends to decrease the adhesion of the films. The internal stresses in the films are regarded as one of the factors in decrease of the adhesion of the films [2]. It is thought that there are two ways to design the interlayers for high adhesion of the films. One is to design the internal stresses in the interlayers which lead to the stress relaxation. However, in the case that the thickness of the films is several hundred times larger than that of the interlayers, stress relaxation of the thick films by interlayers could be hardly expected. Therefore, we have studied the other way, which is to design the internal stresses in the interlayers in order not to cause the internal stress mismatch. The schematic diagram of the interlayers for the thick films on the tungsten carbide substrates is shown in Fig. 1.
* Corresponding author. Fax: + 81-75-882-4120; email: [email protected].
I VD method
c
Fig. I. The schematic diagram of the thick films on the Si-Ni interlayers on the tungsten carbide substrate.
The thick films are formed by cathodic arc ion-plating method and have gradient structures which consist of Ni and TIN. The thick films have high hardness and high toughness [3]. The interlayers require the good adhesion for the tungsten carbide substrates and the Ni-TiN gradient films. The interlayers have the Si-Ni multilayer structures. The Si layers in the interlayers are used for good adhesion of tungsten carbide substrates. The Ni layers in the interlayers are used for good adhesion of the Ni-TiN gradient films. The interlayers are prepared by ion beam and vapor deposition (IVD) method. In this paper, we report on the effect of the interlayers on the adhesion of the 400 km thick films in terms of the internal stress matching.
0168-583X/97/$17.00 Copyright 0 1997 Elsevier Science B.V. All rights reserved PII SO168-583X(96)00399-0
Y. Murakami et al./Nucl.
Instr. and Meth. in Phys. Res. B 121 (1997) 212-215
213
2. Experimental The equipment used for the interlayer preparation was an IVD system, detail of which have been described elsewhere 141. The Si films were prepared by evaporation of silicon and simultaneous irradiation with argon ions on the tungsten carbide substrates (WC-Co). lhe energy of ion bombardment was changed at 0.5, 2.0 and 10.0 keV. The transport ratios of silicon atoms to argon ions, Si/Ar, to the substrates were constant at 7.5. The Si film thickness was changed from 0 to 0.2 m. After the Si films deposition, the Ni films were also prepared by evaporation of nickel and simultaneous irradiation with argon ions. The energy of argon ion bombardment was changed at 0.5, 2.0 and 10.0 keV. The transport ratios, Ni/Ar, were kept at 10. The thickness of Ni films was kept at 1 km. The substrates were kept at low temperature during deposition by water cooling system. After the samples were fractured with a hammer, the cross sections of the samples were examined by scanning electron microscopy GEM) to confirm whether the films peeled from the substrates or not. The internal stresses in the films were measured by the displacements of the Si wafers as substrates after deposition.
3. Results and discussion In the case of the interlayers of which Si films were prepared 0.05 p,rn and 0.10 km with 10.0 keV ion irradiation and the Ni films with 10.0 keV, (Si : 0.05 km, 10.0
Fig. 2. The cross section of the thick films after hammer test in the case of Si films 0.05 km of 10.0 keV and Ni films of 10.0 keV.
keV/Ni: 10.0 keV) and (Si: 0.1 pm, 10.0 keV/Ni: 10.0 keV), the 400 pm thick films could be formed. After hammering, the exfoliation could not be observed in these films as shown in Fig. 2. In the case of the interlayers consisting of only Ni films (without Si films), the 400 pm thick films could not be prepared. The exfoliation faces were analyzed by Auger electron spectroscopy (AES). Fig. 3 shows the AES spectra of the exfoliation face of the substrate side in the case of the Ni interlayers prepared at the energy of 10.0 keV. In this figure, the peaks of tungsten (W), which is the element of substrates, are observed. Therefore, this sample peeled off between the Ni films in the interlayers and the tungsten carbide substrates. It seems that the interlayers need Si
Ni
1000 KINETIC ENERGY (eV) Fig. 3. The AES spectrum of the exfoliation face in the case of the only Ni films of 10.0 keV in interlayer. III. FILM FORMATION
Y. Murakami
214
0.0 ~,‘//I”“, 0 1
i
,I/, 3
1
et al./Nucl.
~
1
~
4
j’
6
7
layers
which
-1.5
“-
I”/”
8
$
10
~
!
0.05
0.00
have good adhesion
and internal
for the tungsten
carbide substrates. In the case of the other Si film conditions and/or Ni film conditions of the interlayers, the thick films also peeled off just after the 400 pm or less deposition. From these results, it seems that the adhesion of the thick films depends strongly on the conditions of the Si-Ni interlayers. The effect of the stress conditions in the interlayers on the adhesion of the thick films is studied in terms of stress matching. Fig. 4 shows the relation between the film thickness and the internal stress in the case of the Ni films by cathodic arc ion-plating (C-AIP), which correspond to
I
j 0, 10
0. 15
0.20
W
0 5 keV 0
2.0 keV
A
IO 0 keV
Fig. 5. The relationship between the Si tilm thickness and internal stresses at various ion energies.
the lower layer of thick films. The internal stresses are constant about 0.6 GPa in tensile stress from 2 km to 10 pm. The thinner C-AIP Ni films, the larger the internal stress as tensile. Therefore, it appears that the near-interface layer in the Ni-TiN thick film is in the state of the large tensile stress. By our previous studies, Ni films prepared with 0.5, 2.0 and 10.0 keV argon ion irradiation, where transport ratios Ni/Ar = 10, were 0.4 GPa in compression, 0.44 GPa in tension and 0.90 GPa in tension. respectively [5]. The
4000
500
1000
KINETIC ENERGY Fig. 6. The AES spectrum of the exfoliation
i 0.25
FILM THICKNESS(Dm)
FILM THICKNESS(,um)
Fig. 4. The relationship between the film thickness stresses in the lower Ni layer of the thick films.
lower
Instr. and Meth. in Phys. Res. B 121 (1997) 212-215
1500
2000
(eV)
face in the case of Si films 0.1 Frn of 10.0 keV and Ni films of 10.0 keV.
Y. Murukrrmi
et ul./Nucl.
Instr. und Mrth.
magnitude of the internal stresses in Ni interlayers with 10.0 keV is the nearest magnitude of the internal stresses in the Ni lower layers of the thick films. Therefore, it seems that the Ni films with 10.0 keV have the improvement effect in adhesion of the thick films because of the good stress matching. In order to study the effect of the Si films conditions on the adhesion of thick films, the internal stresses in Si films were also investigated. The relationship between the Si film thickness and internal stresses at various ion energies is shown in Fig. 5. The internal stresses in the Si films with 0.5 keV and 2.0 keV are only compressive stresses. On the other hand, the internal stresses in the Si films with 10.0 keV are changed from compressive stresses to tensile stresses with decreasing of the film thickness. It has become clear that the Si films also have tensile stresses in the case of the 400 Frn which could be formed. Fig. 6 shows the exfoliation face after rhe thick films deposition in the case of the magnitude of the internal stresses in Si films that are different from those in Ni films. This interlayer consists of the 0.1 pm Si film of 2.0 keV nncl the Ni film of 10.0 keV. In this figure, it appears that the sample peeled off between Si and Ni in interlayer, as the peaks of Ni and Si are observed from this exfoliation place of the sample. It is thought that the difference of the internal stresses in each film causes the peeling off between the interfaces. From these results, it is thought that it is possible to improve the adhesion of the thick films by decreasing internal stress mismatch among the lower layers of the thick films. as well as upper and lower layers of interlayers.
in Phy.1. Ra.
B IZI
215
119971212-215
4. Conclusions We have studied the effect of the interlayers on the adhesion of 400 pm thick films. As a result, it seems that it is possible to improve the adhesion of the thick films by decreasing internal stress mismatch among the lower layers of the thick films, upper layers of interlayers and lower layers of interlayers.
Acknowledgements This work was conducted in the frame of the program on Advanced Chemical Processing Technology, consigned to ACTA from NEDO, which is carried out under the Industrial Science and Technology Frontier Program enforced by the Agency of Industrial Science and Technol-
ogy.
References [I]
J.E.E.Baglin.
[2] S.G.Croll,
Nucl. Instr. and Meth. B 65 (1992)
J. Coat. Technol. 52 (1980)
[3] A.Nakayama.
T.Yoshioka
and T.Nomura,
cation Technologies, eds. T.S.Sudarshan, and K.Kamata [4] K.Ogata,
(The Institute of Materials,
Y.Andoh
119.
35. in: Surface ModifiK.lshizaki.
M.Takata
1994) p. 3 15.
and Kamijo, Nucl. Instr. and Meth. B 33
( 1988) 685. [5] N.Kuratani,
O.Imai,
Coat. Technol. 66
A.Ebe, S.Nishiyama
(I 994)
and K.Ogata.
Surf.
3 IO.
III. FILM
FORMATlON