Highlights

Microstructure of Superhard Nanocrytalline Films

Scientific Achievement

Thin film coatings (a few microns in thickness) are widely used for protecting bulk materials from abrasion, corrosion, or for reducing friction/wear.  Exemplary applications include cutting tools, engines, artificial bones, microelectromechanical devices, spacecrafts, etc.  The purpose of this proposal is to search for the structure-property relationship between microstructure of the nanocrystalline MoN:Cu coatings and the mechanical properties.  By examining the microstructure of the nanocrystalline films using the SEM of the EMC, we have discovered that the morphology of the films is significantly affected by the film processing conditions.  For example, Cu concentration in the sputtered MoN films determines the surface roughness and the columnar structure of the films.  There is also a close relation between the morphology of the film and the mechanical properties such as hardness and friction.  In conjunction with work at the Advanced Photon Source, we were able to reveal the relationship between the microstructure and the residual stresses inside the coatings, which leads to a better understating of the unusual properties of the coatings.

Significance

The study has potential to enable new applications of the MoN:Cu films for heavy vehicles.  Due to their high hardness and low friction, these coatings could be used for protecting engines from wear and, in the meantime, increasing the fuel efficiency of engines.  A part of this work has been published in Appl. Phys. Lett. 89, 172104 (2006).

Performers

G. Chen, D. Singh (Argonne-ET)