Search for content and authors
 

Nanostructure Functionally Graded Coatings Based on Multilayered Carbides

Isaac Dahan 1Moshe P. Dariel 2Naum Frage 2

1. Nuclear Research Center Negv (NRCN), Department of Physics, Beer-Sheva 84190, Israel
2. Ben-Gurion University of the Negev, Department of Materials Engineering (BGU), Beer-Sheva 84105, Israel

Abstract

Within the framework of the present study, we produced functionally graded (FG) Ti/TiC and Nb/NbC multilayered coatings using a magnetron sputtering system. The composition gradient was generated by varying the relative thickness of the as-deposited metal and carbide layers. Subsequent short diffusion treatments were aimed at eliminating the interfaces between the adjacent layers yet maintaining an overall carbon composition gradient across the thickness of the coating.

We were able to determine the diffusivities of carbon in the TiC layer at different temperatures and, hence, the activation energy, 132 kJ/mole, which is one third that for bulk activation energy. The diffusion coefficients were 3.5x10-18- 5.7x10-15 cm2/s for the temperatures range of 355-550°C. These values are significantly higher than expected from extrapolation of data obtained at elevated temperatures.

The triboligical properties were carried out on coatings consisting of graded Ti-TiC multilayers with different concentration profiles and that had been deposited on WC-Co substrates in two steps. First, 0.5µm thick graded Ti-TiC multilayers were deposited followed by a 2.5µm outer layer of stoichiometric TiC. A critical load ,Lc >27N in the as deposited and post annealed coating was observed for a Ti-rich profile The normal wear resistance in the Ti- rich profile was higher by one order of magnitude than for the other profiles.

The structural evolution of the Nb/NbC multilayers was carried at the temperature range of 400-800°C. At these temperatures, the changes of the relative amount of the phases present are due to the mobility of the carbon atoms. The Nb2C structure was found to have an orthorhombic structure, in contrast to the expected from the phase diagram.

 

Legal notice
  • Legal notice:
 

Related papers

Presentation: Oral at E-MRS Fall Meeting 2006, Symposium A, by Isaac Dahan
See On-line Journal of E-MRS Fall Meeting 2006

Submitted: 2006-05-07 20:33
Revised:   2009-06-07 00:44