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Comparative study of the tribological behavior of thermal sprayed quasicrystalline coating layers
Journal of Alloys and Compounds 342 (2002) 321–325
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Comparative study of the tribological behavior of thermal sprayed quasicrystalline coating layers a, a a a b c d E. Fleury *, Y.-C. Kim , J.-S. Kim , D.-H. Kim , W.T. Kim , H.-S. Ahn , S.-M. Lee a
Yonsei University, Center for Noncrystalline Materials, Seoul, South Korea b Chongju University, Department of Physics, Chongju, South Korea c KIST, Tribology Research Center, Seoul, South Korea d Korea Institute of Industrial Technology, Inchon, South Korea
Abstract To investigate the role of tribological reactions on the friction and wear of quasicrystalline materials, coatings with two alloy compositions have been prepared by plasma and HVOF spraying techniques. The tribolayers were characterized by the formation of a transfer film on the counterface and densification of the coating subsurfaces. It was observed that the thickness of the transfer film and pore-free region were dependent on the composition and process used for the deposition of the coatings as well as the sliding velocity. As the sliding velocity increased, the growth rate of the transfer film decreased, resulting in a decrease of the coefficient of friction. On the other hand, the wear rate appeared to be controlled by the thickness of the pore-free region formed within the coating surface zone. 2002 Elsevier Science B.V. All rights reserved. Keywords: Quasicrystalline coatings; Tribolayers; Materials transfer; Coating densification; Friction; Wear
1. Introduction Surface properties of quasicrystalline materials have received considerable attention since the last decade owing to their low surface energy and low friction. Following the first investigation by Kang et al. [1], a wide range of techniques have been used to evaluate the tribological properties of quasicrystals [2–6]. Although the origin of the low friction property still remains unclear, it was shown that values of the coefficient of friction of quasicrystals are lower than those of conventional alloys and ceramics [1,6,7]. Quasicrystalline materials are naturally covered by thin oxide layers, which have been suggested as one possible factor responsible for their excellent tribological properties [5,8]. However, several studies have reported the formation of a transfer film during dry sliding friction and the presence of debris on the wear track that alters the friction and wear performances of quasicrystals [6,8,9]. In this paper, we compare the tribological behavior of *Corresponding author. Center for Noncrystalline Materials, Department of Metallurgical Engineering, Yonsei University, 134 Shinshondong, Seodaemon-ku, Seoul 120-749, South Korea. Tel.: 182-23-614254; fax: 182-23-128-281. E-mail address: [email protected] (E. Fleury).
Al–Cu–Fe–Cr–B and Al–Ni–Co–Si quasicrystalline coatings prepared by plasma and HVOF spraying techniques. Tests were performed under various sliding velocities in order to form tribolayers of different thicknesses that might provide important insight on their role in the friction and wear mechanisms.
2. Experimental details Coating layers with a thickness of about 300 mm were deposited by air plasma and HVOF spraying techniques onto a stainless steel substrate. Processing conditions for plasma and HVOF spraying have been reported elsewhere [6]. Major phases in Al–Cu–Fe–Cr–B coatings were the decagonal, icosahedral and approximant phases, while Al– Ni–Co–Si coatings were essentially composed by the decagonal quasicrystalline phase (Table 1). Friction and wear properties were determined at room temperature under dry condition using a flat-on-flat apparatus with a reciprocating motion [10]. The counterpart material was made of cast iron plated with a 140 mm thick Cr coating. The sliding velocity range was 0.14–0.56 ms 21 . Characterization of the coating layers and track surfaces was made using optical microscopy, microhardness in-
0925-8388 / 02 / $ – see front matter 2002 Elsevier Science B.V. All rights reserved. PII: S0925-8388( 02 )00246-3
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E. Fleury et al. / Journal of Alloys and Compounds 342 (2002) 321 – 325
Table 1 Composition, phase constituents, porosity level and microhardness of the quasicrystalline coatings Coatings and counterpart materials
Phase constituents
Porosity level (%)
Vickers microhardness (kg / mm 2 )
Al–Cu–Fe–Cr–B
Plasma HVOF
d1i1a1l1b d1i1a1l1b
12.662.1 6.961.8
584643 605634
Al–Ni–Co–Si
Plasma HVOF
d1g d1g
11.861.8 6.361.1
559646 577650
Cr
Electroplating
–
–
dentation testing and scanning electron microscopy (SEMEDS).
3. Results Values of the coefficient of friction of the two coatings corresponding to the steady state regime are plotted in Fig. 1. Depending on the coating composition and processing, values were found to vary between 0.45 and 0.53 at the low sliding velocity, and between 0.37 and 0.46 at the higher sliding velocity. These results demonstrated the dependence of the coefficient of friction of these quasicrystalline coatings on the sliding velocity; the higher the sliding velocity, the lower the coefficient of friction [11]. Fig. 1 also revealed a significant influence of the processing condition. Coatings with low porosity content and high microhardness, such as those prepared by HVOF spraying technique (Table 1), have lower values of the coefficient of friction.
Fig. 1. Steady state values of the coefficient of friction of Al–Cu–Fe– Cr–B and Al–Ni–Co–Si quasicrystalline coatings tested at the sliding velocities 0.14 and 0.56 ms 21 .
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Under the same test conditions and deposition technique, compositional and phase constituent effects on the friction could also be detected. Values of the coefficient of friction of Al–Cu–Fe–Cr–B were generally lower than those of Al–Ni–Co–Si coatings. However, Al–Ni–Co–Si HVOF coatings, tested at a high sliding velocity, exhibited the lowest value of the coefficient of friction. In the sliding velocity range of this study, the wear rate of Al–Cu–Fe–Cr–B coatings deposited by the plasma spraying technique was lower than that of Al–Ni–Co–Si plasma coatings; however, Al–Ni–Co–Si coatings were more resistant to dry sliding when prepared by the HVOF technique (Fig. 2). This suggests that the deposition technique played a critical role in the wear performance. Under these testing conditions, the wear resistance of HVOF coatings was about 23 to 65% higher than plasma coatings, depending on the alloy systems. The wear rate was also found to be dependent on the sliding velocity. The wear rate decreased as the sliding velocity increased. However, the HVOF coatings seem to be less dependent than the plasma-sprayed coatings, and it can even be
Fig. 2. Wear rates of Al–Cu–Fe–Cr–B and Al–Ni–Co–Si quasicrystalline coatings tested at the sliding velocities 0.14 and 0.56 ms 21 .
E. Fleury et al. / Journal of Alloys and Compounds 342 (2002) 321 – 325
noticed that the wear rate of Al–Ni–Co–Si HVOF coatings was independent of the sliding velocity.
4. Discussion The relative motion between two solids in contact does not occur continuously but rather by a succession of stick and slip [12]. The stick phase is controlled by the shear strength of the adhesive bond created at micro-contacts between asperities and the mechanical properties of the materials. If the energy of the adhesive bond becomes larger than the energy to propagate underlying cracks, wear particles are detached. During the sliding of quasicrystalline coatings that are brittle in nature, part of the wear debris generated by fracture mechanisms remained in the surface track, where it is subjected to continuous fracture and eventually transferred to the Cr coated disc to form a patch discontinuous layer as shown in Fig. 3a and c. EDS and XRD analyses indicated that the transfer film and wear debris were comprised of materials from the coating and counterpart disc [11]. Consequently, the friction system
323
under dry sliding conditions has evolved from quasicrystal against Cr coated disc into quasicrystal against transfer film layer. This configuration is very similar to the sliding of self-mated materials that traditionally led to large values of the coefficient of friction [13,14]. Under dry sliding conditions, the thickness of the transfer film increased linearly with the sliding distance. It was also found that, for the same number of cycles, low sliding velocities were favorable for the formation of thicker transfer film layers, which is in agreement with an increase of the adhesive bond created at micro-contacts with the time in contact suggested by Bowden and Tabor [12]. The role of the transfer film is illustrated in Fig. 4 with a linear relationship between the growth rate of the transfer film and the coefficient of friction. The sliding velocity dependence of the quasicrystalline coatings can thus be understood as a result of bonding and cohesive rupture leading to the material transfer. Comparison of Fig. 3a and c indicated different thicknesses of the transfer film between Al–Cu–Fe–Cr–B and Al–Ni–Co–Si coatings. Surface properties of the alloy might have some influence on the material transfer from
Fig. 3. SEM micrographs of the counterpart disc and plasma coatings after friction test at the sliding velocity 0.14 ms 21 : (a) counterpart disc tested against Al–Cu–Fe–Cr–B plasma coating, (b) Al–Cu–Fe–Cr–B plasma coating, (c) counterpart disc tested against Al–Ni–Co–Si plasma coating, and (d) Al–Ni–Co–Si plasma coating.
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E. Fleury et al. / Journal of Alloys and Compounds 342 (2002) 321 – 325
pore-free region and the wear rate can be worked out, as shown in Fig. 5, which suggests that the modification of the microstructure by a sintering-like effect controls the wear rate.
5. Conclusions
Fig. 4. Evolution of the coefficient of friction as a function of the growth rate of transfer film.
the coating to the counterface. However, distinct curves for plasma-sprayed and HVOF coatings suggest that the transfer for both coatings might be essentially controlled by the deposition process through the porosity level and presence of micro-cracks, which influences mechanical properties such as the hardness, shear strength and fracture toughness. A conspicuously dense region without pores and microcracks can be detected in the top layer of the coatings (Fig. 3b and d). On account of the low thermal conductivity of QC coatings, high temperatures can arise at the contact surface. Its superimposition to the local shear stress caused a sintering-like effect, resulting in an increase of the microhardness [11]. The pore-free regions formed at the subsurface were thicker in the softer Al–Ni–Co–Si in comparison to Al–Cu–Fe–Cr–B coatings. Our experimental results also indicated that the densification was more easily achieved under high sliding velocity, owing to the larger friction heat, and in coatings that have an initial low porosity level. A correlation between the thickness of the
Fig. 5. Evolution of the wear rate as a function of the thickness of the pore-free region.
Compositional and phase constituent effects on the tribological behavior could be detected, however, steady state values of the coefficient of friction were found to be significantly dependent on the deposition technique. The harder Al–Cu–Fe–Cr–B coatings exhibited low friction and good wear resistance, however, the best performance was obtained for Al–Ni–Co–Si coatings prepared by HVOF technique. The roles of the transfer film and pore-free region on the friction and wear performances have been demonstrated. The formation of transfer film was found to be responsible for the increase of the coefficient of friction, while the densification of the subsurface of the coatings appeared to be favorable for the reduction of wear rate. The structure of the transfer film and subsurface coating layers and their mechanical and physical properties need further investigation.
Acknowledgements The authors are grateful for the financial support by the Creative Research initiatives of the Korean Ministry of Science and Technology.
References [1] S.S. Kang, J.M. Dubois, J. von Stebut, J. Mater. Res. 8 (10) (1993) 2471. [2] S. De Palo, S. Usmani, K. Kishi, S. Sampath, D.J. Sordelet, M.F. Besser, in: Proc. 15th International Thermal Spray Conference, Nice, France, 1998, p. 705. [3] D.J. Sordelet, M.F. Besser, J.L. Logsdon, Mater. Sci. Eng. A255 (1998) 54. [4] C.I. Lang, D. Shechtman, E.J. Gonzales, Bull. Mater. Sci. 22 (3) (1999) 189. [5] J.S. Ko, A.J. Gellman, T.A. Lograsso, C.J. Jenks, P.A. Thiel, Surf. Sci. 426 (1999) 243. [6] S.M. Lee, E. Fleury, J.S. Kim, Y.C. Kim, D.H. Kim, W.T. Kim, H.S. Ahn, to appear in Proc. of the Material Research Society Symposium on Quasicrystals, held in Boston, MA, 2000. [7] D.J. Sordelet, J.S. Kim, M.F. Besser, Mater. Res. Soc. Symp. Proc. 553 (1999) 459. [8] I.L. Singer, J.M. Dubois, J.M. Soro, D. Rouxel, J. von Stebut, in: S. Takeuchi, T. Fujiwara (Eds.), Proc. of the 6th Int. Conf. on Quasicrystals, World Scientific, Singapore, 1997, p. 769. [9] J. von Stebut, J.M. Soro, P. Plaindoux, J.M. Dubois, in: A.I. Goldman, D.J. Sordelet, P.A. Thiel, J.M. Dubois (Eds.), New
E. Fleury et al. / Journal of Alloys and Compounds 342 (2002) 321 – 325 Horizons in Quasicrystals: Research and Applications, World Scientific, Singapore, 1996, p. 248. [10] H.S. Ahn, J.Y. Kim, D.S. Lim, Wear 203–204 (1997) 77. [11] E. Fleury, Y.C. Kim, J.S. Kim, H.S. Ahn, S.M. Lee, W.T. Kim, D.H. Kim, J. Mater. Res. 17 (2) (2002) 492.
325
[12] F.P. Bowden, D. Tabor, The Friction and Lubrification of Solids, Clarendon Press, Oxford, England, 1964. [13] M. Godet, Wear 100 (1984) 437. [14] P.J. Blau, Friction Science and Technology, Marcel Dekker, New York, 1996.
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www.elsevier.com / locate / jallcom
Comparative study of the tribological behavior of thermal sprayed quasicrystalline coating layers a, a a a b c d E. Fleury *, Y.-C. Kim , J.-S. Kim , D.-H. Kim , W.T. Kim , H.-S. Ahn , S.-M. Lee a
Yonsei University, Center for Noncrystalline Materials, Seoul, South Korea b Chongju University, Department of Physics, Chongju, South Korea c KIST, Tribology Research Center, Seoul, South Korea d Korea Institute of Industrial Technology, Inchon, South Korea
Abstract To investigate the role of tribological reactions on the friction and wear of quasicrystalline materials, coatings with two alloy compositions have been prepared by plasma and HVOF spraying techniques. The tribolayers were characterized by the formation of a transfer film on the counterface and densification of the coating subsurfaces. It was observed that the thickness of the transfer film and pore-free region were dependent on the composition and process used for the deposition of the coatings as well as the sliding velocity. As the sliding velocity increased, the growth rate of the transfer film decreased, resulting in a decrease of the coefficient of friction. On the other hand, the wear rate appeared to be controlled by the thickness of the pore-free region formed within the coating surface zone. 2002 Elsevier Science B.V. All rights reserved. Keywords: Quasicrystalline coatings; Tribolayers; Materials transfer; Coating densification; Friction; Wear
1. Introduction Surface properties of quasicrystalline materials have received considerable attention since the last decade owing to their low surface energy and low friction. Following the first investigation by Kang et al. [1], a wide range of techniques have been used to evaluate the tribological properties of quasicrystals [2–6]. Although the origin of the low friction property still remains unclear, it was shown that values of the coefficient of friction of quasicrystals are lower than those of conventional alloys and ceramics [1,6,7]. Quasicrystalline materials are naturally covered by thin oxide layers, which have been suggested as one possible factor responsible for their excellent tribological properties [5,8]. However, several studies have reported the formation of a transfer film during dry sliding friction and the presence of debris on the wear track that alters the friction and wear performances of quasicrystals [6,8,9]. In this paper, we compare the tribological behavior of *Corresponding author. Center for Noncrystalline Materials, Department of Metallurgical Engineering, Yonsei University, 134 Shinshondong, Seodaemon-ku, Seoul 120-749, South Korea. Tel.: 182-23-614254; fax: 182-23-128-281. E-mail address: [email protected] (E. Fleury).
Al–Cu–Fe–Cr–B and Al–Ni–Co–Si quasicrystalline coatings prepared by plasma and HVOF spraying techniques. Tests were performed under various sliding velocities in order to form tribolayers of different thicknesses that might provide important insight on their role in the friction and wear mechanisms.
2. Experimental details Coating layers with a thickness of about 300 mm were deposited by air plasma and HVOF spraying techniques onto a stainless steel substrate. Processing conditions for plasma and HVOF spraying have been reported elsewhere [6]. Major phases in Al–Cu–Fe–Cr–B coatings were the decagonal, icosahedral and approximant phases, while Al– Ni–Co–Si coatings were essentially composed by the decagonal quasicrystalline phase (Table 1). Friction and wear properties were determined at room temperature under dry condition using a flat-on-flat apparatus with a reciprocating motion [10]. The counterpart material was made of cast iron plated with a 140 mm thick Cr coating. The sliding velocity range was 0.14–0.56 ms 21 . Characterization of the coating layers and track surfaces was made using optical microscopy, microhardness in-
0925-8388 / 02 / $ – see front matter 2002 Elsevier Science B.V. All rights reserved. PII: S0925-8388( 02 )00246-3
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E. Fleury et al. / Journal of Alloys and Compounds 342 (2002) 321 – 325
Table 1 Composition, phase constituents, porosity level and microhardness of the quasicrystalline coatings Coatings and counterpart materials
Phase constituents
Porosity level (%)
Vickers microhardness (kg / mm 2 )
Al–Cu–Fe–Cr–B
Plasma HVOF
d1i1a1l1b d1i1a1l1b
12.662.1 6.961.8
584643 605634
Al–Ni–Co–Si
Plasma HVOF
d1g d1g
11.861.8 6.361.1
559646 577650
Cr
Electroplating
–
–
dentation testing and scanning electron microscopy (SEMEDS).
3. Results Values of the coefficient of friction of the two coatings corresponding to the steady state regime are plotted in Fig. 1. Depending on the coating composition and processing, values were found to vary between 0.45 and 0.53 at the low sliding velocity, and between 0.37 and 0.46 at the higher sliding velocity. These results demonstrated the dependence of the coefficient of friction of these quasicrystalline coatings on the sliding velocity; the higher the sliding velocity, the lower the coefficient of friction [11]. Fig. 1 also revealed a significant influence of the processing condition. Coatings with low porosity content and high microhardness, such as those prepared by HVOF spraying technique (Table 1), have lower values of the coefficient of friction.
Fig. 1. Steady state values of the coefficient of friction of Al–Cu–Fe– Cr–B and Al–Ni–Co–Si quasicrystalline coatings tested at the sliding velocities 0.14 and 0.56 ms 21 .
1003633
Under the same test conditions and deposition technique, compositional and phase constituent effects on the friction could also be detected. Values of the coefficient of friction of Al–Cu–Fe–Cr–B were generally lower than those of Al–Ni–Co–Si coatings. However, Al–Ni–Co–Si HVOF coatings, tested at a high sliding velocity, exhibited the lowest value of the coefficient of friction. In the sliding velocity range of this study, the wear rate of Al–Cu–Fe–Cr–B coatings deposited by the plasma spraying technique was lower than that of Al–Ni–Co–Si plasma coatings; however, Al–Ni–Co–Si coatings were more resistant to dry sliding when prepared by the HVOF technique (Fig. 2). This suggests that the deposition technique played a critical role in the wear performance. Under these testing conditions, the wear resistance of HVOF coatings was about 23 to 65% higher than plasma coatings, depending on the alloy systems. The wear rate was also found to be dependent on the sliding velocity. The wear rate decreased as the sliding velocity increased. However, the HVOF coatings seem to be less dependent than the plasma-sprayed coatings, and it can even be
Fig. 2. Wear rates of Al–Cu–Fe–Cr–B and Al–Ni–Co–Si quasicrystalline coatings tested at the sliding velocities 0.14 and 0.56 ms 21 .
E. Fleury et al. / Journal of Alloys and Compounds 342 (2002) 321 – 325
noticed that the wear rate of Al–Ni–Co–Si HVOF coatings was independent of the sliding velocity.
4. Discussion The relative motion between two solids in contact does not occur continuously but rather by a succession of stick and slip [12]. The stick phase is controlled by the shear strength of the adhesive bond created at micro-contacts between asperities and the mechanical properties of the materials. If the energy of the adhesive bond becomes larger than the energy to propagate underlying cracks, wear particles are detached. During the sliding of quasicrystalline coatings that are brittle in nature, part of the wear debris generated by fracture mechanisms remained in the surface track, where it is subjected to continuous fracture and eventually transferred to the Cr coated disc to form a patch discontinuous layer as shown in Fig. 3a and c. EDS and XRD analyses indicated that the transfer film and wear debris were comprised of materials from the coating and counterpart disc [11]. Consequently, the friction system
323
under dry sliding conditions has evolved from quasicrystal against Cr coated disc into quasicrystal against transfer film layer. This configuration is very similar to the sliding of self-mated materials that traditionally led to large values of the coefficient of friction [13,14]. Under dry sliding conditions, the thickness of the transfer film increased linearly with the sliding distance. It was also found that, for the same number of cycles, low sliding velocities were favorable for the formation of thicker transfer film layers, which is in agreement with an increase of the adhesive bond created at micro-contacts with the time in contact suggested by Bowden and Tabor [12]. The role of the transfer film is illustrated in Fig. 4 with a linear relationship between the growth rate of the transfer film and the coefficient of friction. The sliding velocity dependence of the quasicrystalline coatings can thus be understood as a result of bonding and cohesive rupture leading to the material transfer. Comparison of Fig. 3a and c indicated different thicknesses of the transfer film between Al–Cu–Fe–Cr–B and Al–Ni–Co–Si coatings. Surface properties of the alloy might have some influence on the material transfer from
Fig. 3. SEM micrographs of the counterpart disc and plasma coatings after friction test at the sliding velocity 0.14 ms 21 : (a) counterpart disc tested against Al–Cu–Fe–Cr–B plasma coating, (b) Al–Cu–Fe–Cr–B plasma coating, (c) counterpart disc tested against Al–Ni–Co–Si plasma coating, and (d) Al–Ni–Co–Si plasma coating.
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E. Fleury et al. / Journal of Alloys and Compounds 342 (2002) 321 – 325
pore-free region and the wear rate can be worked out, as shown in Fig. 5, which suggests that the modification of the microstructure by a sintering-like effect controls the wear rate.
5. Conclusions
Fig. 4. Evolution of the coefficient of friction as a function of the growth rate of transfer film.
the coating to the counterface. However, distinct curves for plasma-sprayed and HVOF coatings suggest that the transfer for both coatings might be essentially controlled by the deposition process through the porosity level and presence of micro-cracks, which influences mechanical properties such as the hardness, shear strength and fracture toughness. A conspicuously dense region without pores and microcracks can be detected in the top layer of the coatings (Fig. 3b and d). On account of the low thermal conductivity of QC coatings, high temperatures can arise at the contact surface. Its superimposition to the local shear stress caused a sintering-like effect, resulting in an increase of the microhardness [11]. The pore-free regions formed at the subsurface were thicker in the softer Al–Ni–Co–Si in comparison to Al–Cu–Fe–Cr–B coatings. Our experimental results also indicated that the densification was more easily achieved under high sliding velocity, owing to the larger friction heat, and in coatings that have an initial low porosity level. A correlation between the thickness of the
Fig. 5. Evolution of the wear rate as a function of the thickness of the pore-free region.
Compositional and phase constituent effects on the tribological behavior could be detected, however, steady state values of the coefficient of friction were found to be significantly dependent on the deposition technique. The harder Al–Cu–Fe–Cr–B coatings exhibited low friction and good wear resistance, however, the best performance was obtained for Al–Ni–Co–Si coatings prepared by HVOF technique. The roles of the transfer film and pore-free region on the friction and wear performances have been demonstrated. The formation of transfer film was found to be responsible for the increase of the coefficient of friction, while the densification of the subsurface of the coatings appeared to be favorable for the reduction of wear rate. The structure of the transfer film and subsurface coating layers and their mechanical and physical properties need further investigation.
Acknowledgements The authors are grateful for the financial support by the Creative Research initiatives of the Korean Ministry of Science and Technology.
References [1] S.S. Kang, J.M. Dubois, J. von Stebut, J. Mater. Res. 8 (10) (1993) 2471. [2] S. De Palo, S. Usmani, K. Kishi, S. Sampath, D.J. Sordelet, M.F. Besser, in: Proc. 15th International Thermal Spray Conference, Nice, France, 1998, p. 705. [3] D.J. Sordelet, M.F. Besser, J.L. Logsdon, Mater. Sci. Eng. A255 (1998) 54. [4] C.I. Lang, D. Shechtman, E.J. Gonzales, Bull. Mater. Sci. 22 (3) (1999) 189. [5] J.S. Ko, A.J. Gellman, T.A. Lograsso, C.J. Jenks, P.A. Thiel, Surf. Sci. 426 (1999) 243. [6] S.M. Lee, E. Fleury, J.S. Kim, Y.C. Kim, D.H. Kim, W.T. Kim, H.S. Ahn, to appear in Proc. of the Material Research Society Symposium on Quasicrystals, held in Boston, MA, 2000. [7] D.J. Sordelet, J.S. Kim, M.F. Besser, Mater. Res. Soc. Symp. Proc. 553 (1999) 459. [8] I.L. Singer, J.M. Dubois, J.M. Soro, D. Rouxel, J. von Stebut, in: S. Takeuchi, T. Fujiwara (Eds.), Proc. of the 6th Int. Conf. on Quasicrystals, World Scientific, Singapore, 1997, p. 769. [9] J. von Stebut, J.M. Soro, P. Plaindoux, J.M. Dubois, in: A.I. Goldman, D.J. Sordelet, P.A. Thiel, J.M. Dubois (Eds.), New
E. Fleury et al. / Journal of Alloys and Compounds 342 (2002) 321 – 325 Horizons in Quasicrystals: Research and Applications, World Scientific, Singapore, 1996, p. 248. [10] H.S. Ahn, J.Y. Kim, D.S. Lim, Wear 203–204 (1997) 77. [11] E. Fleury, Y.C. Kim, J.S. Kim, H.S. Ahn, S.M. Lee, W.T. Kim, D.H. Kim, J. Mater. Res. 17 (2) (2002) 492.
325
[12] F.P. Bowden, D. Tabor, The Friction and Lubrification of Solids, Clarendon Press, Oxford, England, 1964. [13] M. Godet, Wear 100 (1984) 437. [14] P.J. Blau, Friction Science and Technology, Marcel Dekker, New York, 1996.