Titanium-aluminium-nitride(Ti_(1-x)Al_(x)N)coatings were deposited by close-field un balanced magnetron sputtering on M42 steel substrates and WC-6wt%Co inserts at 450℃.The tribological behavior was analyzed by slidi...Titanium-aluminium-nitride(Ti_(1-x)Al_(x)N)coatings were deposited by close-field un balanced magnetron sputtering on M42 steel substrates and WC-6wt%Co inserts at 450℃.The tribological behavior was analyzed by sliding against steel and WC-6wt%Co balls,while the turning performance was evaluated by a conventional tu rning machine at high cutting speeds without using coolants.In the tribological tests,the formation of transfer layer and the variations of hardness of the co atings played an important role for sliding against steel balls.For the coating s sliding against WC-6wt%Co balls,the Ti-Al-N coatings showed a similar frictio n coefficient,but the TiN coating exhibited a lower value.The difference could be explained by the tri-oxidation wear mechanism.In the turning tests,a super ior cutting performance of the coating was found at x=0.45,which endured 38 min utes before the tool flank wear reached the maximum value of 0.3mm,whereas only 20 minutes were endured for the TiN coating.The excellent performance of the c oatings in the turning tests could be explained by the enhanced mechanical prope rties and oxidation/diffusion resistance of the coatings.展开更多
New multilayer coatings were produced by incorporating alternating soft and hard DLC layers enabled by varying the bias voltage during deposition process while maintaining a constant hard-to-soft layer thickness ratio...New multilayer coatings were produced by incorporating alternating soft and hard DLC layers enabled by varying the bias voltage during deposition process while maintaining a constant hard-to-soft layer thickness ratio.These coatings were deposited onto a Cr/Cr Cxgraded layer by closed field unbalanced magnetron sputtering(CFUBMS).The cross-sectional analysis of the coatings showed that the multilayer coatings possess sharp interfaces between the soft and hard layers with the hard to soft layer thickness ratio(1:1.33)constant in all the coatings.Raman analysis uncovered the increasing sp^(3)character of the DLC coatings as a result of decreasing ID/IGratio and increasing full width at half maximum(FWHM)values of the G band peak induced supposedly by an increase in bias voltage during hard layer deposition.Nanoindentation tests showed an increase in hardness of the DLC coatings which can be correlated with the increase in the sp^(3)content of the coatings as well as decreasing sp^(2)-C cluster size,as calculated from the ID/IGratio.Furthermore,the coatings exhibited excellent plastic deformation resistance and adhesion strength upon microindentation and scratch testing,respectively.Although further investigations are required to assess coating durability,the multilayer design could offer the DLC coatings with a rare opportunity to combine the high hardness with damage resistance with a constant bilayer thickness and without the need to introduce complex multilayer system.展开更多
Ti-Si-N hard coatings were deposited on steel substrates by reactive unbalanced magnetron sputtering from Ti and Si elemental targets in a mixture of Ar and N2 gases.The influences of negative bias voltage(in the rang...Ti-Si-N hard coatings were deposited on steel substrates by reactive unbalanced magnetron sputtering from Ti and Si elemental targets in a mixture of Ar and N2 gases.The influences of negative bias voltage(in the range of-30 to-80 V)on the mechanical properties of the coatings were investigated.In particular,the critical cycle during dynamic impact tests was employed to indicate the bonding strength of the coatings.It was found that the Ti-Si-N coatings prepared at lower constant bias voltages could effectively improve the adhesion and the cyclic impact performance,but their hardness was dropped significantly to 13 GPa at a bias of-30 V.Higher bias voltage values induced greater hardness.A maximum hardness of 47 GPa was obtained at a bias of-60 V.However,the coating adhesion was worse in this case,and the number of impact cycles(～8×10 3)that the coatings could endure was much shorter than that of TiN binary coatings(～2×104).On the other hand,the bias voltage was varied linearly from-40 to-60 V during Ti-Si-N deposition.Under this circumstance,the hardness of the coatings deposited with the bias-graded configuration remained very high(42 GPa),and the adhesion strength was improved substantially.Also,the critical impact cycle could reach as high as 1.8×104.Therefore,bias-graded deposition can provide an effective processing route to prepare Ti-Si-N superhard coatings with high adhesion strength and impact resistance.展开更多
基金The authors wish 10 thank the use of the facilities in ACARL which is suppored by the Innovation Technology Fund of Hong KongPWS acknowledges the support of the research scholarship from the City University of Hong Kong and ME thanks the financial support by a grant awarded by the Research Grant Council of the Hong Kong Special Administrative Region,China(No.CityU 1180/01E)
文摘Titanium-aluminium-nitride(Ti_(1-x)Al_(x)N)coatings were deposited by close-field un balanced magnetron sputtering on M42 steel substrates and WC-6wt%Co inserts at 450℃.The tribological behavior was analyzed by sliding against steel and WC-6wt%Co balls,while the turning performance was evaluated by a conventional tu rning machine at high cutting speeds without using coolants.In the tribological tests,the formation of transfer layer and the variations of hardness of the co atings played an important role for sliding against steel balls.For the coating s sliding against WC-6wt%Co balls,the Ti-Al-N coatings showed a similar frictio n coefficient,but the TiN coating exhibited a lower value.The difference could be explained by the tri-oxidation wear mechanism.In the turning tests,a super ior cutting performance of the coating was found at x=0.45,which endured 38 min utes before the tool flank wear reached the maximum value of 0.3mm,whereas only 20 minutes were endured for the TiN coating.The excellent performance of the c oatings in the turning tests could be explained by the enhanced mechanical prope rties and oxidation/diffusion resistance of the coatings.
基金support from the Australian Government Research Training Program Scholarship。
文摘New multilayer coatings were produced by incorporating alternating soft and hard DLC layers enabled by varying the bias voltage during deposition process while maintaining a constant hard-to-soft layer thickness ratio.These coatings were deposited onto a Cr/Cr Cxgraded layer by closed field unbalanced magnetron sputtering(CFUBMS).The cross-sectional analysis of the coatings showed that the multilayer coatings possess sharp interfaces between the soft and hard layers with the hard to soft layer thickness ratio(1:1.33)constant in all the coatings.Raman analysis uncovered the increasing sp^(3)character of the DLC coatings as a result of decreasing ID/IGratio and increasing full width at half maximum(FWHM)values of the G band peak induced supposedly by an increase in bias voltage during hard layer deposition.Nanoindentation tests showed an increase in hardness of the DLC coatings which can be correlated with the increase in the sp^(3)content of the coatings as well as decreasing sp^(2)-C cluster size,as calculated from the ID/IGratio.Furthermore,the coatings exhibited excellent plastic deformation resistance and adhesion strength upon microindentation and scratch testing,respectively.Although further investigations are required to assess coating durability,the multilayer design could offer the DLC coatings with a rare opportunity to combine the high hardness with damage resistance with a constant bilayer thickness and without the need to introduce complex multilayer system.
基金Applied Research Grant(ARG)of City University of Hong Kong(9667026)
文摘Ti-Si-N hard coatings were deposited on steel substrates by reactive unbalanced magnetron sputtering from Ti and Si elemental targets in a mixture of Ar and N2 gases.The influences of negative bias voltage(in the range of-30 to-80 V)on the mechanical properties of the coatings were investigated.In particular,the critical cycle during dynamic impact tests was employed to indicate the bonding strength of the coatings.It was found that the Ti-Si-N coatings prepared at lower constant bias voltages could effectively improve the adhesion and the cyclic impact performance,but their hardness was dropped significantly to 13 GPa at a bias of-30 V.Higher bias voltage values induced greater hardness.A maximum hardness of 47 GPa was obtained at a bias of-60 V.However,the coating adhesion was worse in this case,and the number of impact cycles(～8×10 3)that the coatings could endure was much shorter than that of TiN binary coatings(～2×104).On the other hand,the bias voltage was varied linearly from-40 to-60 V during Ti-Si-N deposition.Under this circumstance,the hardness of the coatings deposited with the bias-graded configuration remained very high(42 GPa),and the adhesion strength was improved substantially.Also,the critical impact cycle could reach as high as 1.8×104.Therefore,bias-graded deposition can provide an effective processing route to prepare Ti-Si-N superhard coatings with high adhesion strength and impact resistance.
