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892019 Tribological properties of Cr- and Ti-doped MoS2 composite coatings under different humidity atmosphere
Tribological properties of Cr- and Ti-doped MoS2 composite coatings under different
humidity atmosphere
Xing-zhao Ding a XT Zeng a XY He b Z Chen b
a Singapore Institute of Manufacturing Technology 71 Nanyang Drive Singapore 638075 Singaporeb School of Materials Science and Engineering Nanyang Technological University Nanyang Avenue Singapore 639798 Singapore
a b s t r a c ta r t i c l e i n f o
Article history
Received 6 May 2010Accepted in revised form 19 June 2010
Available online 1 July 2010
Keywords
Physical vapor deposition
MoS2-metal composite coatings
Tribological properties
Hardness
Humidity atmosphere
Solid-lubricant MoS2 coatings have been successfully applied in high vacuum and aerospace environments
However these coatings are very sensitive to water vapor and not suitable for applications in moist
environments In this work Cr- and T-doped MoS2 composite coatings were developed The results
demonstrated that these composite coatings are promising for applications in high humidity environments
MoS2ndashCr and MoS2ndashTi composite coatings with different Cr or Ti content were deposited on high speed steel
substrate by unbalanced magnetron sputtering The composition microstructure and mechanical properties
of the as-deposited MoS2-metal composite coatings were analyzed by energy dispersive analysis of X-ray
(EDX) X-ray diffraction (XRD) and nanoindentation experiments The tribological properties of the coatings
were evaluated against an alumina ball under different relative humidity atmosphere using a ball-on-disc
tribometer The MoS2ndashCr and MoS2ndashTi coatings showed a maximum hardness of 75 GPa and 84 GPa at a
dopant content of 166 at Cr or 202 at Ti respectively The tribological test results showed that with a
small amount of Cr andor Ti doping the tribological properties of MoS 2 coatings under humid atmosphere
could be signi1047297cantly improved The optimum doping level was found to be around 10 at for both MoS 2ndashCr
coatings and MoS2ndashTi coatings to show the best tribological properties with both the lowest friction
coef 1047297cient and wear rate The excellent tribological properties of the MoS2ndashCr and MoS2ndashTi coatings with an
appropriate metal doping level in moist atmosphere are found due to their ability to form stable transfer
layer on the surface of the counterbody which supplies lubrication for the contact surfacecopy 2010 Elsevier BV All rights reserved
1 Introduction
Many industrial and engineering applications require two surfaces
to slide over one another resulting in friction and wear Examples
include various cutting and forming tools and generic wear
components (gears bearings engine parts etc) as well Nowadays
surface coating has increasingly become a routine step in tools
manufacturing industry These tribological coatings can effectively
Fig 8 SEM morphologies (a) of the wear scar and the EDX spectrum (b) on the contacted area on the alumina ball after sliding wear against the MoS2ndashCr (96 at) coating under
RH=75 atmosphere
229 X Ding et al Surface amp Coatings Technology 205 (2010) 224ndash 231
892019 Tribological properties of Cr- and Ti-doped MoS2 composite coatings under different humidity atmosphere
rate in various RH atmosphere indicating that the optimum Ti doping
level for thebestwear resistant MoS2ndashTi coatings is also around 10 at
Fig 7 shows the morphology of the wear scar on the Al2O3 ball and
the corresponding EDX spectrum taken from the contact area after the
sliding wear test against the pure MoS2 coating in a RH=75
atmosphere Only a very little amount of Mo was detected in the
contact area on the alumina ball indicating that there was little MoS2
transfer layer formed on the alumina ball which is responsible for the
higher wear rate of the pure MoS2 coatings in high humid atmosphereThe bad tribological properties of the pure MoS2 coatings under
humidity conditions could be interpreted that the water vapor andor
oxygenatoms go into the space between the sulphur planes disrupt the
bonding between the plane [13] Thus pure MoS2 coating is not able to
form stable transfer layer on the counterbody
Fig 8 shows the morphology of the wear scar on the Al2O3 ball and
the corresponding EDX spectrum taken from the contact area after
sliding against the MoS2ndash96 at Cr composite coating in a 75 RH
atmosphere In contrast to the case against the pure MoS2 coating
evident Mo S and Cr signals were detected in the contact area on the
alumina ball after sliding wear against the MoS2ndash96 at Cr coating
indicating that a transfer layer composed of Mo S and Cr was formed
on the alumina ball The formation of this lubricious transfer layer
prevents the direct contact between the Al2O3 ball and the MoS2ndashCrcoating and results in the lower wear rate of the coating For the
MoS2ndashTi composite coatings with lower Ti content the formation of a
similar lubricious transfer layer on the alumina counterbodys contact
surface was also con1047297rmed as shown in Fig 9 which leads to the
excellent wear resistance of the composite coatings
The addition of a small amount of Cr or Ti atoms might enter the
space between thesulphur planes andprevent thewater vapor entering
the coating The lower doped MoS2ndashCr or MoS2ndashTi coatings still remain
the lamellar base structure of MoS2 material so they are able to form a
stable transfer layer and provide good tribological properties in high
humidity atmosphere However when the limit of the solubility
reaches the Cr or Ti would no longer stay in the interstitial sites but
precipitate out forming a discrete metal or multilayer bad tribological
properties would be observed
4 Conclusions
Pure MoS2 coatings exhibit excellent tribological properties in dry
atmosphere but they are very sensitive to moisture Their friction
coef 1047297cient and wear rate increased signi1047297cantly with the increase of
relative humidity With a small amount of Cr or Ti (le16 at) doping the
tribological properties of the resultant composite coatings remain
excellent even the relative humidity is increased up to 75 When the
doping content is further increased(N20 at) the tribological behavior of
these composite coatings changed distictivelyandtheir wear resistance is
greatly degraded The optimum doping level was found to be around
10 at for both MoS2ndashCr coatings and MoS2ndashTi coatings to show the best
tribological properties with both the lowest friction coef 1047297cient and wear
rate The excellent tribological properties of the MoS2ndashCr and MoS2ndashTi
coatings with an appropriate metal doping level in moist atmosphere are
found dueto their abilityto form stable transfer layer on the surface of the
counterbody which supplies lubrication for the contact surface Theseexcellent tribological properties demonstrated a very promising applica-
bility of the MoS2ndashCr and MoS2ndashTi composite coatings in wide range
working conditions from dry to high humidity atmospheres
Acknowledgements
The authors would like to express their gratitude to Mr Anthony
Yeo and Ms Liu Yuchan for their technical assistance in this work
References
[1] HG Prengel WR Pfouts AT Santhanam Surf Coat Technol 102 (1998) 183[2] A Erdemir Solid lubricants and self-lubricating 1047297lms in B Bhushan (Ed)
Modern Tribology Handbook CRC Press Boca Raton FL 2001 p 787[3] T Spalvins ASLE Trans 12 (1969) 36[4] T Spalvins J Vac Sci Technol A 5 (1987) 212[5] LE Pope JKG Panitz Surf Coat Technol 36 (1988) 341[6] MR Hilton PD Fleischauer Surf Coat Technol 5455 (1992) 435[7] C Donnett JM Martin MT Le M Beiin Tribol Int 29 (1996) 123[8] DG Teer V Bellido-Gonzales J Hampshire UK Patent GB95147732
(19071995) EU Patent 0842306[9] DG Teer JH Hampshire V Bellido EU Patent EU 969249879 (1996)
[10] DG Teer J Hampshire V Fox V Bellido-Gonzalez Surf Coat Technol 94ndash95(1997) 572
[11] NM Renevier H Oosterling U Koumlnig H Dautzenberg BJ Kim L Geppert FGMKoopmans J Leopold Surf Coat Technol 172 (2003) 13
[12] RI Amaro RC Martins JO Seabra NM Renevier DG Teer Tribol Int 38 (2005)423
[13] E Arslan F Buumllbuumll A Alsaran A Celik I Efeoglu Wear 259 (2005) 814[14] M Fenker M Balzer H Kappl A Savan Surf Coat Technol 201 (2006) 4099[15] NMRenevier VCFox DGTeer J Hampshire Surf Coat Technol127 (2000) 24[16] MC SimmondsA SavanE P1047298uumlger H VanSwygenhoven Surf Coat Technol126
(2000) 15
Fig 9 SEM morphologies (a) of the wear scar and the EDX spectrum (b) on the contacted area on the alumina ball after sliding wear against the MoS 2ndashTi (95 at) coating under
RH=75 atmosphere
230 X Ding et al Surface amp Coatings Technology 205 (2010) 224ndash 231
892019 Tribological properties of Cr- and Ti-doped MoS2 composite coatings under different humidity atmosphere
Fig 8 SEM morphologies (a) of the wear scar and the EDX spectrum (b) on the contacted area on the alumina ball after sliding wear against the MoS2ndashCr (96 at) coating under
RH=75 atmosphere
229 X Ding et al Surface amp Coatings Technology 205 (2010) 224ndash 231
892019 Tribological properties of Cr- and Ti-doped MoS2 composite coatings under different humidity atmosphere
rate in various RH atmosphere indicating that the optimum Ti doping
level for thebestwear resistant MoS2ndashTi coatings is also around 10 at
Fig 7 shows the morphology of the wear scar on the Al2O3 ball and
the corresponding EDX spectrum taken from the contact area after the
sliding wear test against the pure MoS2 coating in a RH=75
atmosphere Only a very little amount of Mo was detected in the
contact area on the alumina ball indicating that there was little MoS2
transfer layer formed on the alumina ball which is responsible for the
higher wear rate of the pure MoS2 coatings in high humid atmosphereThe bad tribological properties of the pure MoS2 coatings under
humidity conditions could be interpreted that the water vapor andor
oxygenatoms go into the space between the sulphur planes disrupt the
bonding between the plane [13] Thus pure MoS2 coating is not able to
form stable transfer layer on the counterbody
Fig 8 shows the morphology of the wear scar on the Al2O3 ball and
the corresponding EDX spectrum taken from the contact area after
sliding against the MoS2ndash96 at Cr composite coating in a 75 RH
atmosphere In contrast to the case against the pure MoS2 coating
evident Mo S and Cr signals were detected in the contact area on the
alumina ball after sliding wear against the MoS2ndash96 at Cr coating
indicating that a transfer layer composed of Mo S and Cr was formed
on the alumina ball The formation of this lubricious transfer layer
prevents the direct contact between the Al2O3 ball and the MoS2ndashCrcoating and results in the lower wear rate of the coating For the
MoS2ndashTi composite coatings with lower Ti content the formation of a
similar lubricious transfer layer on the alumina counterbodys contact
surface was also con1047297rmed as shown in Fig 9 which leads to the
excellent wear resistance of the composite coatings
The addition of a small amount of Cr or Ti atoms might enter the
space between thesulphur planes andprevent thewater vapor entering
the coating The lower doped MoS2ndashCr or MoS2ndashTi coatings still remain
the lamellar base structure of MoS2 material so they are able to form a
stable transfer layer and provide good tribological properties in high
humidity atmosphere However when the limit of the solubility
reaches the Cr or Ti would no longer stay in the interstitial sites but
precipitate out forming a discrete metal or multilayer bad tribological
properties would be observed
4 Conclusions
Pure MoS2 coatings exhibit excellent tribological properties in dry
atmosphere but they are very sensitive to moisture Their friction
coef 1047297cient and wear rate increased signi1047297cantly with the increase of
relative humidity With a small amount of Cr or Ti (le16 at) doping the
tribological properties of the resultant composite coatings remain
excellent even the relative humidity is increased up to 75 When the
doping content is further increased(N20 at) the tribological behavior of
these composite coatings changed distictivelyandtheir wear resistance is
greatly degraded The optimum doping level was found to be around
10 at for both MoS2ndashCr coatings and MoS2ndashTi coatings to show the best
tribological properties with both the lowest friction coef 1047297cient and wear
rate The excellent tribological properties of the MoS2ndashCr and MoS2ndashTi
coatings with an appropriate metal doping level in moist atmosphere are
found dueto their abilityto form stable transfer layer on the surface of the
counterbody which supplies lubrication for the contact surface Theseexcellent tribological properties demonstrated a very promising applica-
bility of the MoS2ndashCr and MoS2ndashTi composite coatings in wide range
working conditions from dry to high humidity atmospheres
Acknowledgements
The authors would like to express their gratitude to Mr Anthony
Yeo and Ms Liu Yuchan for their technical assistance in this work
References
[1] HG Prengel WR Pfouts AT Santhanam Surf Coat Technol 102 (1998) 183[2] A Erdemir Solid lubricants and self-lubricating 1047297lms in B Bhushan (Ed)
Modern Tribology Handbook CRC Press Boca Raton FL 2001 p 787[3] T Spalvins ASLE Trans 12 (1969) 36[4] T Spalvins J Vac Sci Technol A 5 (1987) 212[5] LE Pope JKG Panitz Surf Coat Technol 36 (1988) 341[6] MR Hilton PD Fleischauer Surf Coat Technol 5455 (1992) 435[7] C Donnett JM Martin MT Le M Beiin Tribol Int 29 (1996) 123[8] DG Teer V Bellido-Gonzales J Hampshire UK Patent GB95147732
(19071995) EU Patent 0842306[9] DG Teer JH Hampshire V Bellido EU Patent EU 969249879 (1996)
[10] DG Teer J Hampshire V Fox V Bellido-Gonzalez Surf Coat Technol 94ndash95(1997) 572
[11] NM Renevier H Oosterling U Koumlnig H Dautzenberg BJ Kim L Geppert FGMKoopmans J Leopold Surf Coat Technol 172 (2003) 13
[12] RI Amaro RC Martins JO Seabra NM Renevier DG Teer Tribol Int 38 (2005)423
[13] E Arslan F Buumllbuumll A Alsaran A Celik I Efeoglu Wear 259 (2005) 814[14] M Fenker M Balzer H Kappl A Savan Surf Coat Technol 201 (2006) 4099[15] NMRenevier VCFox DGTeer J Hampshire Surf Coat Technol127 (2000) 24[16] MC SimmondsA SavanE P1047298uumlger H VanSwygenhoven Surf Coat Technol126
(2000) 15
Fig 9 SEM morphologies (a) of the wear scar and the EDX spectrum (b) on the contacted area on the alumina ball after sliding wear against the MoS 2ndashTi (95 at) coating under
RH=75 atmosphere
230 X Ding et al Surface amp Coatings Technology 205 (2010) 224ndash 231
892019 Tribological properties of Cr- and Ti-doped MoS2 composite coatings under different humidity atmosphere
Fig 8 SEM morphologies (a) of the wear scar and the EDX spectrum (b) on the contacted area on the alumina ball after sliding wear against the MoS2ndashCr (96 at) coating under
RH=75 atmosphere
229 X Ding et al Surface amp Coatings Technology 205 (2010) 224ndash 231
892019 Tribological properties of Cr- and Ti-doped MoS2 composite coatings under different humidity atmosphere
rate in various RH atmosphere indicating that the optimum Ti doping
level for thebestwear resistant MoS2ndashTi coatings is also around 10 at
Fig 7 shows the morphology of the wear scar on the Al2O3 ball and
the corresponding EDX spectrum taken from the contact area after the
sliding wear test against the pure MoS2 coating in a RH=75
atmosphere Only a very little amount of Mo was detected in the
contact area on the alumina ball indicating that there was little MoS2
transfer layer formed on the alumina ball which is responsible for the
higher wear rate of the pure MoS2 coatings in high humid atmosphereThe bad tribological properties of the pure MoS2 coatings under
humidity conditions could be interpreted that the water vapor andor
oxygenatoms go into the space between the sulphur planes disrupt the
bonding between the plane [13] Thus pure MoS2 coating is not able to
form stable transfer layer on the counterbody
Fig 8 shows the morphology of the wear scar on the Al2O3 ball and
the corresponding EDX spectrum taken from the contact area after
sliding against the MoS2ndash96 at Cr composite coating in a 75 RH
atmosphere In contrast to the case against the pure MoS2 coating
evident Mo S and Cr signals were detected in the contact area on the
alumina ball after sliding wear against the MoS2ndash96 at Cr coating
indicating that a transfer layer composed of Mo S and Cr was formed
on the alumina ball The formation of this lubricious transfer layer
prevents the direct contact between the Al2O3 ball and the MoS2ndashCrcoating and results in the lower wear rate of the coating For the
MoS2ndashTi composite coatings with lower Ti content the formation of a
similar lubricious transfer layer on the alumina counterbodys contact
surface was also con1047297rmed as shown in Fig 9 which leads to the
excellent wear resistance of the composite coatings
The addition of a small amount of Cr or Ti atoms might enter the
space between thesulphur planes andprevent thewater vapor entering
the coating The lower doped MoS2ndashCr or MoS2ndashTi coatings still remain
the lamellar base structure of MoS2 material so they are able to form a
stable transfer layer and provide good tribological properties in high
humidity atmosphere However when the limit of the solubility
reaches the Cr or Ti would no longer stay in the interstitial sites but
precipitate out forming a discrete metal or multilayer bad tribological
properties would be observed
4 Conclusions
Pure MoS2 coatings exhibit excellent tribological properties in dry
atmosphere but they are very sensitive to moisture Their friction
coef 1047297cient and wear rate increased signi1047297cantly with the increase of
relative humidity With a small amount of Cr or Ti (le16 at) doping the
tribological properties of the resultant composite coatings remain
excellent even the relative humidity is increased up to 75 When the
doping content is further increased(N20 at) the tribological behavior of
these composite coatings changed distictivelyandtheir wear resistance is
greatly degraded The optimum doping level was found to be around
10 at for both MoS2ndashCr coatings and MoS2ndashTi coatings to show the best
tribological properties with both the lowest friction coef 1047297cient and wear
rate The excellent tribological properties of the MoS2ndashCr and MoS2ndashTi
coatings with an appropriate metal doping level in moist atmosphere are
found dueto their abilityto form stable transfer layer on the surface of the
counterbody which supplies lubrication for the contact surface Theseexcellent tribological properties demonstrated a very promising applica-
bility of the MoS2ndashCr and MoS2ndashTi composite coatings in wide range
working conditions from dry to high humidity atmospheres
Acknowledgements
The authors would like to express their gratitude to Mr Anthony
Yeo and Ms Liu Yuchan for their technical assistance in this work
References
[1] HG Prengel WR Pfouts AT Santhanam Surf Coat Technol 102 (1998) 183[2] A Erdemir Solid lubricants and self-lubricating 1047297lms in B Bhushan (Ed)
Modern Tribology Handbook CRC Press Boca Raton FL 2001 p 787[3] T Spalvins ASLE Trans 12 (1969) 36[4] T Spalvins J Vac Sci Technol A 5 (1987) 212[5] LE Pope JKG Panitz Surf Coat Technol 36 (1988) 341[6] MR Hilton PD Fleischauer Surf Coat Technol 5455 (1992) 435[7] C Donnett JM Martin MT Le M Beiin Tribol Int 29 (1996) 123[8] DG Teer V Bellido-Gonzales J Hampshire UK Patent GB95147732
(19071995) EU Patent 0842306[9] DG Teer JH Hampshire V Bellido EU Patent EU 969249879 (1996)
[10] DG Teer J Hampshire V Fox V Bellido-Gonzalez Surf Coat Technol 94ndash95(1997) 572
[11] NM Renevier H Oosterling U Koumlnig H Dautzenberg BJ Kim L Geppert FGMKoopmans J Leopold Surf Coat Technol 172 (2003) 13
[12] RI Amaro RC Martins JO Seabra NM Renevier DG Teer Tribol Int 38 (2005)423
[13] E Arslan F Buumllbuumll A Alsaran A Celik I Efeoglu Wear 259 (2005) 814[14] M Fenker M Balzer H Kappl A Savan Surf Coat Technol 201 (2006) 4099[15] NMRenevier VCFox DGTeer J Hampshire Surf Coat Technol127 (2000) 24[16] MC SimmondsA SavanE P1047298uumlger H VanSwygenhoven Surf Coat Technol126
(2000) 15
Fig 9 SEM morphologies (a) of the wear scar and the EDX spectrum (b) on the contacted area on the alumina ball after sliding wear against the MoS 2ndashTi (95 at) coating under
RH=75 atmosphere
230 X Ding et al Surface amp Coatings Technology 205 (2010) 224ndash 231
892019 Tribological properties of Cr- and Ti-doped MoS2 composite coatings under different humidity atmosphere
Fig 8 SEM morphologies (a) of the wear scar and the EDX spectrum (b) on the contacted area on the alumina ball after sliding wear against the MoS2ndashCr (96 at) coating under
RH=75 atmosphere
229 X Ding et al Surface amp Coatings Technology 205 (2010) 224ndash 231
892019 Tribological properties of Cr- and Ti-doped MoS2 composite coatings under different humidity atmosphere
rate in various RH atmosphere indicating that the optimum Ti doping
level for thebestwear resistant MoS2ndashTi coatings is also around 10 at
Fig 7 shows the morphology of the wear scar on the Al2O3 ball and
the corresponding EDX spectrum taken from the contact area after the
sliding wear test against the pure MoS2 coating in a RH=75
atmosphere Only a very little amount of Mo was detected in the
contact area on the alumina ball indicating that there was little MoS2
transfer layer formed on the alumina ball which is responsible for the
higher wear rate of the pure MoS2 coatings in high humid atmosphereThe bad tribological properties of the pure MoS2 coatings under
humidity conditions could be interpreted that the water vapor andor
oxygenatoms go into the space between the sulphur planes disrupt the
bonding between the plane [13] Thus pure MoS2 coating is not able to
form stable transfer layer on the counterbody
Fig 8 shows the morphology of the wear scar on the Al2O3 ball and
the corresponding EDX spectrum taken from the contact area after
sliding against the MoS2ndash96 at Cr composite coating in a 75 RH
atmosphere In contrast to the case against the pure MoS2 coating
evident Mo S and Cr signals were detected in the contact area on the
alumina ball after sliding wear against the MoS2ndash96 at Cr coating
indicating that a transfer layer composed of Mo S and Cr was formed
on the alumina ball The formation of this lubricious transfer layer
prevents the direct contact between the Al2O3 ball and the MoS2ndashCrcoating and results in the lower wear rate of the coating For the
MoS2ndashTi composite coatings with lower Ti content the formation of a
similar lubricious transfer layer on the alumina counterbodys contact
surface was also con1047297rmed as shown in Fig 9 which leads to the
excellent wear resistance of the composite coatings
The addition of a small amount of Cr or Ti atoms might enter the
space between thesulphur planes andprevent thewater vapor entering
the coating The lower doped MoS2ndashCr or MoS2ndashTi coatings still remain
the lamellar base structure of MoS2 material so they are able to form a
stable transfer layer and provide good tribological properties in high
humidity atmosphere However when the limit of the solubility
reaches the Cr or Ti would no longer stay in the interstitial sites but
precipitate out forming a discrete metal or multilayer bad tribological
properties would be observed
4 Conclusions
Pure MoS2 coatings exhibit excellent tribological properties in dry
atmosphere but they are very sensitive to moisture Their friction
coef 1047297cient and wear rate increased signi1047297cantly with the increase of
relative humidity With a small amount of Cr or Ti (le16 at) doping the
tribological properties of the resultant composite coatings remain
excellent even the relative humidity is increased up to 75 When the
doping content is further increased(N20 at) the tribological behavior of
these composite coatings changed distictivelyandtheir wear resistance is
greatly degraded The optimum doping level was found to be around
10 at for both MoS2ndashCr coatings and MoS2ndashTi coatings to show the best
tribological properties with both the lowest friction coef 1047297cient and wear
rate The excellent tribological properties of the MoS2ndashCr and MoS2ndashTi
coatings with an appropriate metal doping level in moist atmosphere are
found dueto their abilityto form stable transfer layer on the surface of the
counterbody which supplies lubrication for the contact surface Theseexcellent tribological properties demonstrated a very promising applica-
bility of the MoS2ndashCr and MoS2ndashTi composite coatings in wide range
working conditions from dry to high humidity atmospheres
Acknowledgements
The authors would like to express their gratitude to Mr Anthony
Yeo and Ms Liu Yuchan for their technical assistance in this work
References
[1] HG Prengel WR Pfouts AT Santhanam Surf Coat Technol 102 (1998) 183[2] A Erdemir Solid lubricants and self-lubricating 1047297lms in B Bhushan (Ed)
Modern Tribology Handbook CRC Press Boca Raton FL 2001 p 787[3] T Spalvins ASLE Trans 12 (1969) 36[4] T Spalvins J Vac Sci Technol A 5 (1987) 212[5] LE Pope JKG Panitz Surf Coat Technol 36 (1988) 341[6] MR Hilton PD Fleischauer Surf Coat Technol 5455 (1992) 435[7] C Donnett JM Martin MT Le M Beiin Tribol Int 29 (1996) 123[8] DG Teer V Bellido-Gonzales J Hampshire UK Patent GB95147732
(19071995) EU Patent 0842306[9] DG Teer JH Hampshire V Bellido EU Patent EU 969249879 (1996)
[10] DG Teer J Hampshire V Fox V Bellido-Gonzalez Surf Coat Technol 94ndash95(1997) 572
[11] NM Renevier H Oosterling U Koumlnig H Dautzenberg BJ Kim L Geppert FGMKoopmans J Leopold Surf Coat Technol 172 (2003) 13
[12] RI Amaro RC Martins JO Seabra NM Renevier DG Teer Tribol Int 38 (2005)423
[13] E Arslan F Buumllbuumll A Alsaran A Celik I Efeoglu Wear 259 (2005) 814[14] M Fenker M Balzer H Kappl A Savan Surf Coat Technol 201 (2006) 4099[15] NMRenevier VCFox DGTeer J Hampshire Surf Coat Technol127 (2000) 24[16] MC SimmondsA SavanE P1047298uumlger H VanSwygenhoven Surf Coat Technol126
(2000) 15
Fig 9 SEM morphologies (a) of the wear scar and the EDX spectrum (b) on the contacted area on the alumina ball after sliding wear against the MoS 2ndashTi (95 at) coating under
RH=75 atmosphere
230 X Ding et al Surface amp Coatings Technology 205 (2010) 224ndash 231
892019 Tribological properties of Cr- and Ti-doped MoS2 composite coatings under different humidity atmosphere
Fig 8 SEM morphologies (a) of the wear scar and the EDX spectrum (b) on the contacted area on the alumina ball after sliding wear against the MoS2ndashCr (96 at) coating under
RH=75 atmosphere
229 X Ding et al Surface amp Coatings Technology 205 (2010) 224ndash 231
892019 Tribological properties of Cr- and Ti-doped MoS2 composite coatings under different humidity atmosphere
rate in various RH atmosphere indicating that the optimum Ti doping
level for thebestwear resistant MoS2ndashTi coatings is also around 10 at
Fig 7 shows the morphology of the wear scar on the Al2O3 ball and
the corresponding EDX spectrum taken from the contact area after the
sliding wear test against the pure MoS2 coating in a RH=75
atmosphere Only a very little amount of Mo was detected in the
contact area on the alumina ball indicating that there was little MoS2
transfer layer formed on the alumina ball which is responsible for the
higher wear rate of the pure MoS2 coatings in high humid atmosphereThe bad tribological properties of the pure MoS2 coatings under
humidity conditions could be interpreted that the water vapor andor
oxygenatoms go into the space between the sulphur planes disrupt the
bonding between the plane [13] Thus pure MoS2 coating is not able to
form stable transfer layer on the counterbody
Fig 8 shows the morphology of the wear scar on the Al2O3 ball and
the corresponding EDX spectrum taken from the contact area after
sliding against the MoS2ndash96 at Cr composite coating in a 75 RH
atmosphere In contrast to the case against the pure MoS2 coating
evident Mo S and Cr signals were detected in the contact area on the
alumina ball after sliding wear against the MoS2ndash96 at Cr coating
indicating that a transfer layer composed of Mo S and Cr was formed
on the alumina ball The formation of this lubricious transfer layer
prevents the direct contact between the Al2O3 ball and the MoS2ndashCrcoating and results in the lower wear rate of the coating For the
MoS2ndashTi composite coatings with lower Ti content the formation of a
similar lubricious transfer layer on the alumina counterbodys contact
surface was also con1047297rmed as shown in Fig 9 which leads to the
excellent wear resistance of the composite coatings
The addition of a small amount of Cr or Ti atoms might enter the
space between thesulphur planes andprevent thewater vapor entering
the coating The lower doped MoS2ndashCr or MoS2ndashTi coatings still remain
the lamellar base structure of MoS2 material so they are able to form a
stable transfer layer and provide good tribological properties in high
humidity atmosphere However when the limit of the solubility
reaches the Cr or Ti would no longer stay in the interstitial sites but
precipitate out forming a discrete metal or multilayer bad tribological
properties would be observed
4 Conclusions
Pure MoS2 coatings exhibit excellent tribological properties in dry
atmosphere but they are very sensitive to moisture Their friction
coef 1047297cient and wear rate increased signi1047297cantly with the increase of
relative humidity With a small amount of Cr or Ti (le16 at) doping the
tribological properties of the resultant composite coatings remain
excellent even the relative humidity is increased up to 75 When the
doping content is further increased(N20 at) the tribological behavior of
these composite coatings changed distictivelyandtheir wear resistance is
greatly degraded The optimum doping level was found to be around
10 at for both MoS2ndashCr coatings and MoS2ndashTi coatings to show the best
tribological properties with both the lowest friction coef 1047297cient and wear
rate The excellent tribological properties of the MoS2ndashCr and MoS2ndashTi
coatings with an appropriate metal doping level in moist atmosphere are
found dueto their abilityto form stable transfer layer on the surface of the
counterbody which supplies lubrication for the contact surface Theseexcellent tribological properties demonstrated a very promising applica-
bility of the MoS2ndashCr and MoS2ndashTi composite coatings in wide range
working conditions from dry to high humidity atmospheres
Acknowledgements
The authors would like to express their gratitude to Mr Anthony
Yeo and Ms Liu Yuchan for their technical assistance in this work
References
[1] HG Prengel WR Pfouts AT Santhanam Surf Coat Technol 102 (1998) 183[2] A Erdemir Solid lubricants and self-lubricating 1047297lms in B Bhushan (Ed)
Modern Tribology Handbook CRC Press Boca Raton FL 2001 p 787[3] T Spalvins ASLE Trans 12 (1969) 36[4] T Spalvins J Vac Sci Technol A 5 (1987) 212[5] LE Pope JKG Panitz Surf Coat Technol 36 (1988) 341[6] MR Hilton PD Fleischauer Surf Coat Technol 5455 (1992) 435[7] C Donnett JM Martin MT Le M Beiin Tribol Int 29 (1996) 123[8] DG Teer V Bellido-Gonzales J Hampshire UK Patent GB95147732
(19071995) EU Patent 0842306[9] DG Teer JH Hampshire V Bellido EU Patent EU 969249879 (1996)
[10] DG Teer J Hampshire V Fox V Bellido-Gonzalez Surf Coat Technol 94ndash95(1997) 572
[11] NM Renevier H Oosterling U Koumlnig H Dautzenberg BJ Kim L Geppert FGMKoopmans J Leopold Surf Coat Technol 172 (2003) 13
[12] RI Amaro RC Martins JO Seabra NM Renevier DG Teer Tribol Int 38 (2005)423
[13] E Arslan F Buumllbuumll A Alsaran A Celik I Efeoglu Wear 259 (2005) 814[14] M Fenker M Balzer H Kappl A Savan Surf Coat Technol 201 (2006) 4099[15] NMRenevier VCFox DGTeer J Hampshire Surf Coat Technol127 (2000) 24[16] MC SimmondsA SavanE P1047298uumlger H VanSwygenhoven Surf Coat Technol126
(2000) 15
Fig 9 SEM morphologies (a) of the wear scar and the EDX spectrum (b) on the contacted area on the alumina ball after sliding wear against the MoS 2ndashTi (95 at) coating under
RH=75 atmosphere
230 X Ding et al Surface amp Coatings Technology 205 (2010) 224ndash 231
892019 Tribological properties of Cr- and Ti-doped MoS2 composite coatings under different humidity atmosphere
Fig 8 SEM morphologies (a) of the wear scar and the EDX spectrum (b) on the contacted area on the alumina ball after sliding wear against the MoS2ndashCr (96 at) coating under
RH=75 atmosphere
229 X Ding et al Surface amp Coatings Technology 205 (2010) 224ndash 231
892019 Tribological properties of Cr- and Ti-doped MoS2 composite coatings under different humidity atmosphere
rate in various RH atmosphere indicating that the optimum Ti doping
level for thebestwear resistant MoS2ndashTi coatings is also around 10 at
Fig 7 shows the morphology of the wear scar on the Al2O3 ball and
the corresponding EDX spectrum taken from the contact area after the
sliding wear test against the pure MoS2 coating in a RH=75
atmosphere Only a very little amount of Mo was detected in the
contact area on the alumina ball indicating that there was little MoS2
transfer layer formed on the alumina ball which is responsible for the
higher wear rate of the pure MoS2 coatings in high humid atmosphereThe bad tribological properties of the pure MoS2 coatings under
humidity conditions could be interpreted that the water vapor andor
oxygenatoms go into the space between the sulphur planes disrupt the
bonding between the plane [13] Thus pure MoS2 coating is not able to
form stable transfer layer on the counterbody
Fig 8 shows the morphology of the wear scar on the Al2O3 ball and
the corresponding EDX spectrum taken from the contact area after
sliding against the MoS2ndash96 at Cr composite coating in a 75 RH
atmosphere In contrast to the case against the pure MoS2 coating
evident Mo S and Cr signals were detected in the contact area on the
alumina ball after sliding wear against the MoS2ndash96 at Cr coating
indicating that a transfer layer composed of Mo S and Cr was formed
on the alumina ball The formation of this lubricious transfer layer
prevents the direct contact between the Al2O3 ball and the MoS2ndashCrcoating and results in the lower wear rate of the coating For the
MoS2ndashTi composite coatings with lower Ti content the formation of a
similar lubricious transfer layer on the alumina counterbodys contact
surface was also con1047297rmed as shown in Fig 9 which leads to the
excellent wear resistance of the composite coatings
The addition of a small amount of Cr or Ti atoms might enter the
space between thesulphur planes andprevent thewater vapor entering
the coating The lower doped MoS2ndashCr or MoS2ndashTi coatings still remain
the lamellar base structure of MoS2 material so they are able to form a
stable transfer layer and provide good tribological properties in high
humidity atmosphere However when the limit of the solubility
reaches the Cr or Ti would no longer stay in the interstitial sites but
precipitate out forming a discrete metal or multilayer bad tribological
properties would be observed
4 Conclusions
Pure MoS2 coatings exhibit excellent tribological properties in dry
atmosphere but they are very sensitive to moisture Their friction
coef 1047297cient and wear rate increased signi1047297cantly with the increase of
relative humidity With a small amount of Cr or Ti (le16 at) doping the
tribological properties of the resultant composite coatings remain
excellent even the relative humidity is increased up to 75 When the
doping content is further increased(N20 at) the tribological behavior of
these composite coatings changed distictivelyandtheir wear resistance is
greatly degraded The optimum doping level was found to be around
10 at for both MoS2ndashCr coatings and MoS2ndashTi coatings to show the best
tribological properties with both the lowest friction coef 1047297cient and wear
rate The excellent tribological properties of the MoS2ndashCr and MoS2ndashTi
coatings with an appropriate metal doping level in moist atmosphere are
found dueto their abilityto form stable transfer layer on the surface of the
counterbody which supplies lubrication for the contact surface Theseexcellent tribological properties demonstrated a very promising applica-
bility of the MoS2ndashCr and MoS2ndashTi composite coatings in wide range
working conditions from dry to high humidity atmospheres
Acknowledgements
The authors would like to express their gratitude to Mr Anthony
Yeo and Ms Liu Yuchan for their technical assistance in this work
References
[1] HG Prengel WR Pfouts AT Santhanam Surf Coat Technol 102 (1998) 183[2] A Erdemir Solid lubricants and self-lubricating 1047297lms in B Bhushan (Ed)
Modern Tribology Handbook CRC Press Boca Raton FL 2001 p 787[3] T Spalvins ASLE Trans 12 (1969) 36[4] T Spalvins J Vac Sci Technol A 5 (1987) 212[5] LE Pope JKG Panitz Surf Coat Technol 36 (1988) 341[6] MR Hilton PD Fleischauer Surf Coat Technol 5455 (1992) 435[7] C Donnett JM Martin MT Le M Beiin Tribol Int 29 (1996) 123[8] DG Teer V Bellido-Gonzales J Hampshire UK Patent GB95147732
(19071995) EU Patent 0842306[9] DG Teer JH Hampshire V Bellido EU Patent EU 969249879 (1996)
[10] DG Teer J Hampshire V Fox V Bellido-Gonzalez Surf Coat Technol 94ndash95(1997) 572
[11] NM Renevier H Oosterling U Koumlnig H Dautzenberg BJ Kim L Geppert FGMKoopmans J Leopold Surf Coat Technol 172 (2003) 13
[12] RI Amaro RC Martins JO Seabra NM Renevier DG Teer Tribol Int 38 (2005)423
[13] E Arslan F Buumllbuumll A Alsaran A Celik I Efeoglu Wear 259 (2005) 814[14] M Fenker M Balzer H Kappl A Savan Surf Coat Technol 201 (2006) 4099[15] NMRenevier VCFox DGTeer J Hampshire Surf Coat Technol127 (2000) 24[16] MC SimmondsA SavanE P1047298uumlger H VanSwygenhoven Surf Coat Technol126
(2000) 15
Fig 9 SEM morphologies (a) of the wear scar and the EDX spectrum (b) on the contacted area on the alumina ball after sliding wear against the MoS 2ndashTi (95 at) coating under
RH=75 atmosphere
230 X Ding et al Surface amp Coatings Technology 205 (2010) 224ndash 231
892019 Tribological properties of Cr- and Ti-doped MoS2 composite coatings under different humidity atmosphere
rate in various RH atmosphere indicating that the optimum Ti doping
level for thebestwear resistant MoS2ndashTi coatings is also around 10 at
Fig 7 shows the morphology of the wear scar on the Al2O3 ball and
the corresponding EDX spectrum taken from the contact area after the
sliding wear test against the pure MoS2 coating in a RH=75
atmosphere Only a very little amount of Mo was detected in the
contact area on the alumina ball indicating that there was little MoS2
transfer layer formed on the alumina ball which is responsible for the
higher wear rate of the pure MoS2 coatings in high humid atmosphereThe bad tribological properties of the pure MoS2 coatings under
humidity conditions could be interpreted that the water vapor andor
oxygenatoms go into the space between the sulphur planes disrupt the
bonding between the plane [13] Thus pure MoS2 coating is not able to
form stable transfer layer on the counterbody
Fig 8 shows the morphology of the wear scar on the Al2O3 ball and
the corresponding EDX spectrum taken from the contact area after
sliding against the MoS2ndash96 at Cr composite coating in a 75 RH
atmosphere In contrast to the case against the pure MoS2 coating
evident Mo S and Cr signals were detected in the contact area on the
alumina ball after sliding wear against the MoS2ndash96 at Cr coating
indicating that a transfer layer composed of Mo S and Cr was formed
on the alumina ball The formation of this lubricious transfer layer
prevents the direct contact between the Al2O3 ball and the MoS2ndashCrcoating and results in the lower wear rate of the coating For the
MoS2ndashTi composite coatings with lower Ti content the formation of a
similar lubricious transfer layer on the alumina counterbodys contact
surface was also con1047297rmed as shown in Fig 9 which leads to the
excellent wear resistance of the composite coatings
The addition of a small amount of Cr or Ti atoms might enter the
space between thesulphur planes andprevent thewater vapor entering
the coating The lower doped MoS2ndashCr or MoS2ndashTi coatings still remain
the lamellar base structure of MoS2 material so they are able to form a
stable transfer layer and provide good tribological properties in high
humidity atmosphere However when the limit of the solubility
reaches the Cr or Ti would no longer stay in the interstitial sites but
precipitate out forming a discrete metal or multilayer bad tribological
properties would be observed
4 Conclusions
Pure MoS2 coatings exhibit excellent tribological properties in dry
atmosphere but they are very sensitive to moisture Their friction
coef 1047297cient and wear rate increased signi1047297cantly with the increase of
relative humidity With a small amount of Cr or Ti (le16 at) doping the
tribological properties of the resultant composite coatings remain
excellent even the relative humidity is increased up to 75 When the
doping content is further increased(N20 at) the tribological behavior of
these composite coatings changed distictivelyandtheir wear resistance is
greatly degraded The optimum doping level was found to be around
10 at for both MoS2ndashCr coatings and MoS2ndashTi coatings to show the best
tribological properties with both the lowest friction coef 1047297cient and wear
rate The excellent tribological properties of the MoS2ndashCr and MoS2ndashTi
coatings with an appropriate metal doping level in moist atmosphere are
found dueto their abilityto form stable transfer layer on the surface of the
counterbody which supplies lubrication for the contact surface Theseexcellent tribological properties demonstrated a very promising applica-
bility of the MoS2ndashCr and MoS2ndashTi composite coatings in wide range
working conditions from dry to high humidity atmospheres
Acknowledgements
The authors would like to express their gratitude to Mr Anthony
Yeo and Ms Liu Yuchan for their technical assistance in this work
References
[1] HG Prengel WR Pfouts AT Santhanam Surf Coat Technol 102 (1998) 183[2] A Erdemir Solid lubricants and self-lubricating 1047297lms in B Bhushan (Ed)
Modern Tribology Handbook CRC Press Boca Raton FL 2001 p 787[3] T Spalvins ASLE Trans 12 (1969) 36[4] T Spalvins J Vac Sci Technol A 5 (1987) 212[5] LE Pope JKG Panitz Surf Coat Technol 36 (1988) 341[6] MR Hilton PD Fleischauer Surf Coat Technol 5455 (1992) 435[7] C Donnett JM Martin MT Le M Beiin Tribol Int 29 (1996) 123[8] DG Teer V Bellido-Gonzales J Hampshire UK Patent GB95147732
(19071995) EU Patent 0842306[9] DG Teer JH Hampshire V Bellido EU Patent EU 969249879 (1996)
[10] DG Teer J Hampshire V Fox V Bellido-Gonzalez Surf Coat Technol 94ndash95(1997) 572
[11] NM Renevier H Oosterling U Koumlnig H Dautzenberg BJ Kim L Geppert FGMKoopmans J Leopold Surf Coat Technol 172 (2003) 13
[12] RI Amaro RC Martins JO Seabra NM Renevier DG Teer Tribol Int 38 (2005)423
[13] E Arslan F Buumllbuumll A Alsaran A Celik I Efeoglu Wear 259 (2005) 814[14] M Fenker M Balzer H Kappl A Savan Surf Coat Technol 201 (2006) 4099[15] NMRenevier VCFox DGTeer J Hampshire Surf Coat Technol127 (2000) 24[16] MC SimmondsA SavanE P1047298uumlger H VanSwygenhoven Surf Coat Technol126
(2000) 15
Fig 9 SEM morphologies (a) of the wear scar and the EDX spectrum (b) on the contacted area on the alumina ball after sliding wear against the MoS 2ndashTi (95 at) coating under
RH=75 atmosphere
230 X Ding et al Surface amp Coatings Technology 205 (2010) 224ndash 231
892019 Tribological properties of Cr- and Ti-doped MoS2 composite coatings under different humidity atmosphere