AVS 53rd International Symposium
    Advanced Surface Engineering Friday Sessions
       Session SE2-FrM

Paper SE2-FrM11
Synthesis and Tribological Properties of Novel 'Chameleon' Coatings

Friday, November 17, 2006, 11:20 am, Room 2007a

Session: Wear Mechanisms, Tribochemistry and Nanotribology
Presenter: C.C. Baker, North Carolina State University
Authors: C.C. Baker, North Carolina State University
J.J. Hu, Air Force Research Labs, MLBT
A.A. Voevodin, Air Force Research Labs, MLBT
Correspondent: Click to Email
'Chameleon' coatings are nanocomposite coating systems adapt their tribological performance to changes in environmental conditions such as humidity and temperature. In this research we have investigated the tribological properties of two new nanocomposite 'chameleon' coating systems. One of the system includes the incorporation Al2O3 in an Au matrix with diamond like carbon (DLC) and MoS2 nanoparticle inclusions. The coating design approach included a formation of nanocrystalline hard oxide particles for wear resistance, their embedding onto an amorphous matrix for contact toughness enhancement, and inclusion of nanocrystalline and/or amorphous solid lubricants for friction adaptation to different environments. The other coating system that we have studied includes a composite of Rhenium and hexagonal Boron Nitride. Rhenium is a unique ultra hard material that shows low coefficient of friction at elevated temperatures to 700 @degree@C and in vacuum environments, while Boron Nitride is also excellent for high temperatures and for humid environments. All coatings were produced using a combination of laser ablation and magnetron sputtering. Chemical and structural analysis of the coatings included x-ray photoelectron spectroscopy, x-ray diffraction, transmission electron microscopy, and micro-Raman spectroscopy. Mechanical properties such as coating hardness and toughness were investigated using nanoindentation, scratch, and indentation adhesion tests. Friction measurements were studied by cycling between humid air and dry nitrogen conditions, as well as tests at temperatures of up to 700 @degree@C. Both of the new coating systems validate the universality of the 'chameleon' design approach.