Influence of ion bombardment on structure and tribological performance of nanoscale multilayer C/Cr PVD coatings

KOK, Y. N., WEN, J. G., PETROV, I. and HOVSEPIAN, P. E. (2006). Influence of ion bombardment on structure and tribological performance of nanoscale multilayer C/Cr PVD coatings. Surface Engineering, 22 (2), 92-98.

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Link to published version:: 10.1179/174329406X98377

Abstract

Low friction C/Cr coatings have been successfully deposited by the combined steered cathodic arc/unbalanced magnetron sputtering technique. The present paper focuses on the properties, tribological performance and microstructure evolution of C/Cr coatings as a function of the bias voltage U-b ranging from -65 to -350 V. As the bias voltage increases from -65 to -95 V, the structure changes from columnar to dense structure which comprises of randomly distributed onionlike carbon clusters. Further increase in the bias voltage to -350 V led to segregation and self-organisation of the carbon atoms induced by the high energy ion bombardment and finally to the formation of a new type self-organised multilayer structure. On the other hand, the phase composition transforms from graphitic (sp(2) C-C bonded) to Me carbon (Cr-C bonded), where the content of the carbide phase increases with increasing the bias voltage. The C/Cr coatings showed an excellent adhesion (L-c > 70 N), with hardness ranging from 8.23 to 25 GPa depending on the bias voltage. Pin on disc tests showed that the friction coefficient was reduced from 0.22 to 0.16 when the U-b was increased from -65 to -95 V. A strong correlation was found between the microstructure, the residual stress, the sp(2)/sp(3) content and the coating friction behaviour. Dry high speed milling trials on automotive aluminium alloy (Al-Si8Cu(3)Fe) showed that C/Cr coated cemented carbide end mills enhance the tool performance and the tool life compared with the uncoated tools by a factor of 2, suggesting the potential for dry high speed machining of 'sticky' alloys.

Item Type: Article
Research Institute, Centre or Group: Materials and Engineering Research Institute > Thin Films Research Centre > Nanotechnology Centre for PVD Research
Identification Number: 10.1179/174329406X98377
Depositing User: Ann Betterton
Date Deposited: 16 Feb 2010 14:39
Last Modified: 16 Feb 2010 14:39
URI: http://shura.shu.ac.uk/id/eprint/1127

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