Nanostructure and properties of TiC/a-C:H composite coatings
Y.T. Pei, D. Galvan, J.Th.M. De Hosson
Acta Materialia
Abstract
TiC/a-C:H nanocomposite coatings, deposited with closed-eld unbalanced magnetron sputtering, have been scrutinized with atomic force, scanning and high-resolution transmission electron microscopy, nanoindentation and tribo-tests. These coatings con- sist of 2 5 nm TiC nanocrystallites embedded in an amorphous hydrocarbon (a-C:H) matrix. A transition from a columnar to a glassy microstructure has been observed in the nanocomposite coatings with increasing substrate bias or carbon content. Micro- ...Morecracks induced by nanoindentation or sliding wear readily propagate through the column boundaries whereas the coatings without a columnar microstructure exhibit substantial toughness. The toughening of the nanocomposite coatings has been achieved eec- tively on two dierent scales, namely by restraining the formation of columns on a microscale and by manipulating the nanostruc- ture on a nanoscale. The hardness (H) and elastic modulus (E) of the coatings are found to increase monotonically with increasing substrate bias, whereas the ratio of the hardness to the elastic modulus (H/E) remains approximately constant. In contrast, H/E increases with C content. Ball-on-disc tribo-tests conrm that the nanocomposite coatings possess superior wear resistance and strong self-lubrication eects with a coecient of friction as low as 0.05 in ambient air and below 0.02 in dry air, under dry sliding against uncoated bearing steel balls. Physical arguments are presented to explain the toughening mechanism and the ultra-low friction.
keywords:TiC/a-C:H nanocomposite; Thin films; Nanostructure; Magnetron sputtering; Properties
本站文章未经允许不得转载；如欲转载请注明出处，北京桑尧科技开发有限公司网址：http://www.sunspraying.com/
|
