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Study of micromechanical properties of ion-beam mixed tungsten-on-steel layers
Wear 254 (2003) 1037–1041
Study of micromechanical properties of ion-beam mixed tungsten-on-steel layers A. Pi˛atkowska a,∗ , J. Jagielski a,b , G. Gawlik a,b , W. Matz c , E. Richter c , M. Mozetic d , A. Zalar d a
c
Institute of Electronic Materials Technology, Wolczynska 133, 01-919 Warsaw, Poland b The Andrzej Soltan Institute for Nuclear Studies, 05-400 Swierk/Otwock, Poland Institute for Ion Beam Physics and Materials Studies, Forschungszentrum Rossendorf, D-01314 Dresden, Germany d Institute of Surface Engineering and Optoelectronics, Teslova 3, 1000 Ljubljana, Slovenia
Abstract The relations linking structure, microhardness and adhesion were studied for ion-beam mixed tungsten layers deposited on the surface of high-speed steel. The 45 nm thick W layer were mixed with 340 keV Kr ions at temperatures ranging from RT up to 450 ◦ C. The increase of mixing temperature results in partial crystallization of the layers and the increase of the layer hardness. Substantial increase of layer adhesion has been observed in scratch tests for all mixed samples. © 2003 Elsevier Science B.V. All rights reserved. Keywords: Ion-beam mixing; Thin layers; Adhesion; Micromechanical properties
1. Introduction The Fe–W system is characterized by numerous interesting properties. It can be synthesized in amorphous, crystalline or nanostructured phases [1,2]. The amorphous Fe–W phase is stable up to at least 600 ◦ C, it is thus one of the most stables phases among binary iron-based amorphous alloys [1]. The system reveals unusual magnetic properties [1,3], high corrosion resistance, in acid solutions up to 15–20 times higher than 304 stainless steel [4,5]. Recently, it has been shown that micromechanical properties of amorphous Fe–W phase are very advantageous also and the combination of low friction coefficient with low wear rate can be obtained under dry sliding conditions [6]. In most of experiments reported the Fe–W alloy is prepared by using mechanical alloying (MA). Despite the indisputable advantages of this technique such as low cost and ability to prepare alloys of various compositions a severe limitation of MA is that the alloy produced has always a form of powder, its direct application in manufacturing of mechanical elements is thus restricted. For that purpose the methods able to form thin, adherent layer of a given compound on the surface of elements of various shapes and dimensions are required. One can list several techniques well ∗ Corresponding author. E-mail address: [email protected] (A. Pi˛atkowska).
suited for the preparation of thin film coatings, among them a new, promising technique like ion-beam mixing. The method is described in many papers (for a review see e.g. [7]) and offers numerous advantages over classical synthesis or deposition techniques. The most important are: (i) low process temperature, (ii) very high concentrations of impurity atoms and (iii) the absence of any measurable changes in object dimensions or surface finishing. As a result of ion-beam mixing an interface layer composed of mixed substrate and layer materials is formed. In consequence, a continuous transition from layer to substrate takes place, ensuring a very good adhesion of mixed layers to the substrate. The interest of this paper is focused on mechanical properties of the mixed layers and, more specifically, on their adhesion properties.
2. Experimental In the experiments the samples made of high-speed steel of composition: 0.88% C, 6.5% W, 5% Mo, 1.9% V, 0.3% Mn and 0.3% Si, balance Fe, were used. The samples were cut from the same rod of material, hardened and tempered to final hardness of 64 HRC, lapped and polished to the Ra ≈ 10 nm. A 45 nm thick W layer was deposited by means of rf-sputtering device. The tungsten layers were mixed with the substrate by 340 keV Kr ions up to a dose
0043-1648/03/$ – see front matter © 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0043-1648(03)00313-2
1038
A. Pi˛atkowska et al. / Wear 254 (2003) 1037–1041
of 3 × 1016 cm−2 . The mixing processes were performed at RT, 350 or 450 ◦ C. The samples were analyzed by means of Auger electron spectrometry (AES), grazing angle X-ray diffraction (GXRD) and conversion electron Mössbauer spectroscopy (CEMS) techniques. Micromechanical properties such as: microhardness, wear and friction properties and adhesion properties were also measured. Wear and friction tests were performed under dry sliding conditions (air, ∼40% of humidity) in ball-on-flat geometry using a 6.5 mm steel ball as a countersample. The tests were carried out under a load of 20 N. Microhardness data (load–penetration plots) have been recorded by using an ultramicrohardness tester. The scratch tests were conducted using a Shimadzu tester equipped with an oscillating stylus having a tip of 30 m in diameter. The diamond stylus oscillates perpendicularly to the head displacement resulting in characteristic triangular traces on sample surface. The applied load varied from 0 to 500 mN.
3. Results and discussion The detailed discussion of structural properties of ion-beam mixed W/steel layers has been presented in [8], here only a brief summary will be given. The layers mixed at room temperature revealed an amorphous structure (as studied by GXRD and CEMS methods), which persists upon annealing up to at least 450 ◦ C. The increase of the process temperature above 350 ◦ C results in a partial crystallization of the layer, which is composed of the mixture of an amorphous Fe–W and tungsten carbide phases. The depth distribution profiles of W and Fe atoms extracted from AES measurements are shown in Fig. 1. The surface layer of RT-mixed samples is composed of thin residual W layer and relatively thick interface layer. The total thickness of the mixed layer equals to about 50 nm. The tungsten depth distributions in samples mixed at 450 ◦ C became almost flat in the surface region and the interface became slightly narrower suggesting the formation of stable compound. This observation corroborates with the results of structural analysis, more precisely with the formation of tungsten carbide after high temperature ion-beam mixing. The load–penetration plots (ultramicrohardness data) recorded for the samples used in the experiments are shown in Fig. 2. The samples mixed at room temperature are significantly softer than the substrate. The increase of the process temperature leads to the increase of the layer hardness. Once again this observation correlates with the results of structural analysis; the layers mixed at room temperature are fully amorphous, hence softer than the substrate, whereas those mixed at 450 ◦ C contain hard crystalline tungsten carbide phase. The variations of friction coefficient vs. time are shown in Fig. 3. Three stages of wear process can be clearly distinguished: a fast increase of friction coefficient (so called screen removal, i.e. removal of the surface contamination
Fig. 1. The depth distribution profiles of W (black circles) and Fe (open circles) atoms extracted from AES measurements for: as-deposited (a), RT-mixed (b), 350 ◦ C mixed (c) and 450 ◦ C mixed (d) tungsten layers.
from the sample surface), transition stage followed by saturation of friction force. The lowest friction coefficient has been measured for RT-ion-beam mixed layer, the increase of process temperature results in the continuous increase of friction force. The results of scratch tests are shown in Fig. 4. The as-deposited tungsten layers are characterized by poor adhesion; already at the beginning of the test the layer breaks down and delaminates from the substrate. For higher loads the SEM images recorded for as-deposited sample show thin, residual tungsten or tungsten-rich layer on steel surface. It is likely, that tungsten acts as a solid lubricant between scratch tip and the substrate and at higher loads is pressed into a steel substrate. The samples mixed at RT or 450 ◦ C reveal no traces of layer breakdown or delamination. In the case of RT-mixed sample the damage caused by test
A. Pi˛atkowska et al. / Wear 254 (2003) 1037–1041
Fig. 2. The load–penetration plots (ultramicrohardness data) recorded for the samples used in the experiments.
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pin to the substrate begins at lower loads than it is the case of the 450 ◦ C mixed sample. Wear tests performed on the mixed layers reveal that in all cases the wear rate has been substantially reduced when compared to the substrate sample. The detailed data extracted from these measurements are listed in Table 1. A characteristic feature of the wear of a substrate or of an as-deposited sample is the formation of huge bumps at track borders. The EDX analysis performed on wear tracks showed that these regions contain high concentration of oxygen atoms. The dominant wear mechanism in these samples should thus be attributed to oxidation and removal of oxidized wear debris [9,10]. The concentration of oxygen atoms in wear track formed on the surface of mixed samples is much lower and the formation of side bumps strongly reduced. The effect of wear reduction observed in samples with mixed layers should thus be attributed to the decrease of wear-induced oxidation. The results of micromechanical measurements point to direct correlation between the layer structure, hardness and friction properties. The results obtained can be summarized in following points: (i) ion-beam mixing performed at low temperature leads to the formation of a thin, amorphous Fe–W layer, (ii) the increase of process temperature results in a partial crystallization of the layer and the increase of
Fig. 3. The variation of friction coefficient vs. time for samples mixed at temperatures ranging from RT up to 450 ◦ C.
Table 1 Removed and built-up volumes of material in wear tracks formed on the surface of samples No.
Sample
1 2 3
Substrate W layer mixed at RT W layer mixed at 450 ◦ C a
Below measurable limit.
Worn volume
Built-up volume
Absolute (mm2 × m)
Relative
Absolute (mm2 × m)
Relative
0.0150 0.0026 0.0a
1.00 0.17 0.0a
0.02400 0.00056 0.0a
1.000 0.023 0.0a
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A. Pi˛atkowska et al. / Wear 254 (2003) 1037–1041
is thinner than the penetration of countersample during the wear and friction tests. The conditions required by Bowden and Tabor theory for friction reduction are thus fulfilled. On the other hand, lower friction coefficient leads to the decrease of total energy dissipated within the contact area. Accordingly to the model proposed by Gerve [12] this energy causes chemical changes in wear tracks (so called tribomutation), leads to the increase of sample temperature and to the removal of wear debris. The reduction of friction leads thus to a lower wear rate, the main reason for wear reduction seems to be related to the reduction of oxidation during the wear process.
4. Conclusions The results presented in this paper prove the ability of ion-beam mixing technique to efficiently form thin amorphous layers of Fe–W composition. The mixed layers are characterized by a very good adhesion to the surface: on all mixed samples no traces of delamination were observed. The increase of the process temperature leads to partial crystallization of the layer which is composed of the mixture of amorphous Fe–W and crystalline tungsten carbide. The fully amorphous layers are the softest and reveal the lowest friction coefficient. All mixed samples are characterized by significantly reduced wear rate. The results obtained can be explained in the frames of Bowden and Tabor theory and Gerve’s concept of tribomutation. These results contradict somehow a general, “rule-of-thumb”, opinion that only hard coatings are wear resistant. We showed that also thin, soft layers can effectively reduce the wear of steel in dry sliding process. Ion-beam mixing seems to be a method perfectly suited for applications using Bowden and Tabor theory as it allows one to form thin, adherent layers of almost any composition on the surface of substrate material. It is interesting to note that low thickness of layers modified by incoming ion beams is usually regarded as a principal weakness of this technique. In such application as the low friction coatings basing on Bowden and Tabor theory we take advantage of this characteristics, transforming the weakness of the technique into its beneficial property.
Acknowledgements Fig. 4. SEM images of sample surface in the areas of scratch tests.
the layer hardness, (iii) all ion-beam mixed layers are more wear resistant than the steel substrate what is likely related to reduction of the oxidation rate and (iv) all ion-beam mixed layers reveal very good adhesion to the substrate. The results obtained can be explained in the frames of Bowden and Tabor [11] theory of friction. The amorphous layer formed at the sample surface is softer than the substrate material and
Financial support from Polish State Committee for Scientific Research (contract number 7 T08C 030 19) is gratefully acknowledged.
References [1] M. Lu, C.L. Chien, J. Appl. Phys. 67 (1990) 5787–5789. [2] U. Herr, K. Samwer, Nanostruct. Mater. 1 (1992) 515–521.
A. Pi˛atkowska et al. / Wear 254 (2003) 1037–1041 [3] K. Sumiyama, M. Hirata, W. Teshima, Jpn. J. Appl. Phys. 30 (1991) 2839–2845. [4] M. Naka, K. Hashimoto, T. Masumoto, J. Non-Cryst. Solids 29 (1978) 61–65. [5] S. Yao, S. Zhao, H. Guo, M. Kowaka, Corrosion 52 (1996) 183–186. [6] J. Jagielski, A. Pi˛atkowska, Z. Rymuza, Z. Kusznierewicz, D. Treheux, D. Boutard, L. Thome, G. Gawlik, Wear 238 (2000) 48–55. [7] M. Nastasi, J.W. Mayer, Mater. Sci. Eng. R12 (1994) 1–52.
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[8] A. Pi˛atkowska, J. Jagielski, M. Kopcewicz, W. Matz, A. Zalar, M. Mozetic, Nucl. Instr. Meth. B206 (2003) 1052–1055. [9] G. Dearnaley, Nucl. Instr. Meth. B7/8 (1985) 158–165. [10] J. Jagielski, A. Pi˛atkowska, W. Matz, E. Richter, G. Gawlik, A. Turos, Vacuum 63 (4) (2001) 671. [11] F.P. Bowden, D. Tabor, Friction: An Introduction to Tribology, Anchor Press/Doubleday, Garden City, New York, 1973. [12] A. Gerve, Surf. Coat. Technol. 60 (1993) 521–524.
Study of micromechanical properties of ion-beam mixed tungsten-on-steel layers A. Pi˛atkowska a,∗ , J. Jagielski a,b , G. Gawlik a,b , W. Matz c , E. Richter c , M. Mozetic d , A. Zalar d a
c
Institute of Electronic Materials Technology, Wolczynska 133, 01-919 Warsaw, Poland b The Andrzej Soltan Institute for Nuclear Studies, 05-400 Swierk/Otwock, Poland Institute for Ion Beam Physics and Materials Studies, Forschungszentrum Rossendorf, D-01314 Dresden, Germany d Institute of Surface Engineering and Optoelectronics, Teslova 3, 1000 Ljubljana, Slovenia
Abstract The relations linking structure, microhardness and adhesion were studied for ion-beam mixed tungsten layers deposited on the surface of high-speed steel. The 45 nm thick W layer were mixed with 340 keV Kr ions at temperatures ranging from RT up to 450 ◦ C. The increase of mixing temperature results in partial crystallization of the layers and the increase of the layer hardness. Substantial increase of layer adhesion has been observed in scratch tests for all mixed samples. © 2003 Elsevier Science B.V. All rights reserved. Keywords: Ion-beam mixing; Thin layers; Adhesion; Micromechanical properties
1. Introduction The Fe–W system is characterized by numerous interesting properties. It can be synthesized in amorphous, crystalline or nanostructured phases [1,2]. The amorphous Fe–W phase is stable up to at least 600 ◦ C, it is thus one of the most stables phases among binary iron-based amorphous alloys [1]. The system reveals unusual magnetic properties [1,3], high corrosion resistance, in acid solutions up to 15–20 times higher than 304 stainless steel [4,5]. Recently, it has been shown that micromechanical properties of amorphous Fe–W phase are very advantageous also and the combination of low friction coefficient with low wear rate can be obtained under dry sliding conditions [6]. In most of experiments reported the Fe–W alloy is prepared by using mechanical alloying (MA). Despite the indisputable advantages of this technique such as low cost and ability to prepare alloys of various compositions a severe limitation of MA is that the alloy produced has always a form of powder, its direct application in manufacturing of mechanical elements is thus restricted. For that purpose the methods able to form thin, adherent layer of a given compound on the surface of elements of various shapes and dimensions are required. One can list several techniques well ∗ Corresponding author. E-mail address: [email protected] (A. Pi˛atkowska).
suited for the preparation of thin film coatings, among them a new, promising technique like ion-beam mixing. The method is described in many papers (for a review see e.g. [7]) and offers numerous advantages over classical synthesis or deposition techniques. The most important are: (i) low process temperature, (ii) very high concentrations of impurity atoms and (iii) the absence of any measurable changes in object dimensions or surface finishing. As a result of ion-beam mixing an interface layer composed of mixed substrate and layer materials is formed. In consequence, a continuous transition from layer to substrate takes place, ensuring a very good adhesion of mixed layers to the substrate. The interest of this paper is focused on mechanical properties of the mixed layers and, more specifically, on their adhesion properties.
2. Experimental In the experiments the samples made of high-speed steel of composition: 0.88% C, 6.5% W, 5% Mo, 1.9% V, 0.3% Mn and 0.3% Si, balance Fe, were used. The samples were cut from the same rod of material, hardened and tempered to final hardness of 64 HRC, lapped and polished to the Ra ≈ 10 nm. A 45 nm thick W layer was deposited by means of rf-sputtering device. The tungsten layers were mixed with the substrate by 340 keV Kr ions up to a dose
0043-1648/03/$ – see front matter © 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0043-1648(03)00313-2
1038
A. Pi˛atkowska et al. / Wear 254 (2003) 1037–1041
of 3 × 1016 cm−2 . The mixing processes were performed at RT, 350 or 450 ◦ C. The samples were analyzed by means of Auger electron spectrometry (AES), grazing angle X-ray diffraction (GXRD) and conversion electron Mössbauer spectroscopy (CEMS) techniques. Micromechanical properties such as: microhardness, wear and friction properties and adhesion properties were also measured. Wear and friction tests were performed under dry sliding conditions (air, ∼40% of humidity) in ball-on-flat geometry using a 6.5 mm steel ball as a countersample. The tests were carried out under a load of 20 N. Microhardness data (load–penetration plots) have been recorded by using an ultramicrohardness tester. The scratch tests were conducted using a Shimadzu tester equipped with an oscillating stylus having a tip of 30 m in diameter. The diamond stylus oscillates perpendicularly to the head displacement resulting in characteristic triangular traces on sample surface. The applied load varied from 0 to 500 mN.
3. Results and discussion The detailed discussion of structural properties of ion-beam mixed W/steel layers has been presented in [8], here only a brief summary will be given. The layers mixed at room temperature revealed an amorphous structure (as studied by GXRD and CEMS methods), which persists upon annealing up to at least 450 ◦ C. The increase of the process temperature above 350 ◦ C results in a partial crystallization of the layer, which is composed of the mixture of an amorphous Fe–W and tungsten carbide phases. The depth distribution profiles of W and Fe atoms extracted from AES measurements are shown in Fig. 1. The surface layer of RT-mixed samples is composed of thin residual W layer and relatively thick interface layer. The total thickness of the mixed layer equals to about 50 nm. The tungsten depth distributions in samples mixed at 450 ◦ C became almost flat in the surface region and the interface became slightly narrower suggesting the formation of stable compound. This observation corroborates with the results of structural analysis, more precisely with the formation of tungsten carbide after high temperature ion-beam mixing. The load–penetration plots (ultramicrohardness data) recorded for the samples used in the experiments are shown in Fig. 2. The samples mixed at room temperature are significantly softer than the substrate. The increase of the process temperature leads to the increase of the layer hardness. Once again this observation correlates with the results of structural analysis; the layers mixed at room temperature are fully amorphous, hence softer than the substrate, whereas those mixed at 450 ◦ C contain hard crystalline tungsten carbide phase. The variations of friction coefficient vs. time are shown in Fig. 3. Three stages of wear process can be clearly distinguished: a fast increase of friction coefficient (so called screen removal, i.e. removal of the surface contamination
Fig. 1. The depth distribution profiles of W (black circles) and Fe (open circles) atoms extracted from AES measurements for: as-deposited (a), RT-mixed (b), 350 ◦ C mixed (c) and 450 ◦ C mixed (d) tungsten layers.
from the sample surface), transition stage followed by saturation of friction force. The lowest friction coefficient has been measured for RT-ion-beam mixed layer, the increase of process temperature results in the continuous increase of friction force. The results of scratch tests are shown in Fig. 4. The as-deposited tungsten layers are characterized by poor adhesion; already at the beginning of the test the layer breaks down and delaminates from the substrate. For higher loads the SEM images recorded for as-deposited sample show thin, residual tungsten or tungsten-rich layer on steel surface. It is likely, that tungsten acts as a solid lubricant between scratch tip and the substrate and at higher loads is pressed into a steel substrate. The samples mixed at RT or 450 ◦ C reveal no traces of layer breakdown or delamination. In the case of RT-mixed sample the damage caused by test
A. Pi˛atkowska et al. / Wear 254 (2003) 1037–1041
Fig. 2. The load–penetration plots (ultramicrohardness data) recorded for the samples used in the experiments.
1039
pin to the substrate begins at lower loads than it is the case of the 450 ◦ C mixed sample. Wear tests performed on the mixed layers reveal that in all cases the wear rate has been substantially reduced when compared to the substrate sample. The detailed data extracted from these measurements are listed in Table 1. A characteristic feature of the wear of a substrate or of an as-deposited sample is the formation of huge bumps at track borders. The EDX analysis performed on wear tracks showed that these regions contain high concentration of oxygen atoms. The dominant wear mechanism in these samples should thus be attributed to oxidation and removal of oxidized wear debris [9,10]. The concentration of oxygen atoms in wear track formed on the surface of mixed samples is much lower and the formation of side bumps strongly reduced. The effect of wear reduction observed in samples with mixed layers should thus be attributed to the decrease of wear-induced oxidation. The results of micromechanical measurements point to direct correlation between the layer structure, hardness and friction properties. The results obtained can be summarized in following points: (i) ion-beam mixing performed at low temperature leads to the formation of a thin, amorphous Fe–W layer, (ii) the increase of process temperature results in a partial crystallization of the layer and the increase of
Fig. 3. The variation of friction coefficient vs. time for samples mixed at temperatures ranging from RT up to 450 ◦ C.
Table 1 Removed and built-up volumes of material in wear tracks formed on the surface of samples No.
Sample
1 2 3
Substrate W layer mixed at RT W layer mixed at 450 ◦ C a
Below measurable limit.
Worn volume
Built-up volume
Absolute (mm2 × m)
Relative
Absolute (mm2 × m)
Relative
0.0150 0.0026 0.0a
1.00 0.17 0.0a
0.02400 0.00056 0.0a
1.000 0.023 0.0a
1040
A. Pi˛atkowska et al. / Wear 254 (2003) 1037–1041
is thinner than the penetration of countersample during the wear and friction tests. The conditions required by Bowden and Tabor theory for friction reduction are thus fulfilled. On the other hand, lower friction coefficient leads to the decrease of total energy dissipated within the contact area. Accordingly to the model proposed by Gerve [12] this energy causes chemical changes in wear tracks (so called tribomutation), leads to the increase of sample temperature and to the removal of wear debris. The reduction of friction leads thus to a lower wear rate, the main reason for wear reduction seems to be related to the reduction of oxidation during the wear process.
4. Conclusions The results presented in this paper prove the ability of ion-beam mixing technique to efficiently form thin amorphous layers of Fe–W composition. The mixed layers are characterized by a very good adhesion to the surface: on all mixed samples no traces of delamination were observed. The increase of the process temperature leads to partial crystallization of the layer which is composed of the mixture of amorphous Fe–W and crystalline tungsten carbide. The fully amorphous layers are the softest and reveal the lowest friction coefficient. All mixed samples are characterized by significantly reduced wear rate. The results obtained can be explained in the frames of Bowden and Tabor theory and Gerve’s concept of tribomutation. These results contradict somehow a general, “rule-of-thumb”, opinion that only hard coatings are wear resistant. We showed that also thin, soft layers can effectively reduce the wear of steel in dry sliding process. Ion-beam mixing seems to be a method perfectly suited for applications using Bowden and Tabor theory as it allows one to form thin, adherent layers of almost any composition on the surface of substrate material. It is interesting to note that low thickness of layers modified by incoming ion beams is usually regarded as a principal weakness of this technique. In such application as the low friction coatings basing on Bowden and Tabor theory we take advantage of this characteristics, transforming the weakness of the technique into its beneficial property.
Acknowledgements Fig. 4. SEM images of sample surface in the areas of scratch tests.
the layer hardness, (iii) all ion-beam mixed layers are more wear resistant than the steel substrate what is likely related to reduction of the oxidation rate and (iv) all ion-beam mixed layers reveal very good adhesion to the substrate. The results obtained can be explained in the frames of Bowden and Tabor [11] theory of friction. The amorphous layer formed at the sample surface is softer than the substrate material and
Financial support from Polish State Committee for Scientific Research (contract number 7 T08C 030 19) is gratefully acknowledged.
References [1] M. Lu, C.L. Chien, J. Appl. Phys. 67 (1990) 5787–5789. [2] U. Herr, K. Samwer, Nanostruct. Mater. 1 (1992) 515–521.
A. Pi˛atkowska et al. / Wear 254 (2003) 1037–1041 [3] K. Sumiyama, M. Hirata, W. Teshima, Jpn. J. Appl. Phys. 30 (1991) 2839–2845. [4] M. Naka, K. Hashimoto, T. Masumoto, J. Non-Cryst. Solids 29 (1978) 61–65. [5] S. Yao, S. Zhao, H. Guo, M. Kowaka, Corrosion 52 (1996) 183–186. [6] J. Jagielski, A. Pi˛atkowska, Z. Rymuza, Z. Kusznierewicz, D. Treheux, D. Boutard, L. Thome, G. Gawlik, Wear 238 (2000) 48–55. [7] M. Nastasi, J.W. Mayer, Mater. Sci. Eng. R12 (1994) 1–52.
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[8] A. Pi˛atkowska, J. Jagielski, M. Kopcewicz, W. Matz, A. Zalar, M. Mozetic, Nucl. Instr. Meth. B206 (2003) 1052–1055. [9] G. Dearnaley, Nucl. Instr. Meth. B7/8 (1985) 158–165. [10] J. Jagielski, A. Pi˛atkowska, W. Matz, E. Richter, G. Gawlik, A. Turos, Vacuum 63 (4) (2001) 671. [11] F.P. Bowden, D. Tabor, Friction: An Introduction to Tribology, Anchor Press/Doubleday, Garden City, New York, 1973. [12] A. Gerve, Surf. Coat. Technol. 60 (1993) 521–524.