Integrated Nanomechanical Characterisation of Hard Coatings

Advanced nanomechanical and nano/microtribological tests combined with simulated stress distributions help understand performance in tribological applications and to design coating systems for enhanced performance. Detailed simulated stress distributions enable data to be interpreted more effectively, providing mechanistic information to explain where and why coating systems fail in scratch and fretting tests, and then to design coatings with improved performance. In this chapter the combined experimental-modelling approach is illustrated with data from a wide range of coating systems including (i) ion beam assisted Ti(Fe,N)x on silicon, (ii) multilayered hard carbon coatings on steel and (iii) nitride-based coatings on cemented carbide. In applications of hard coatings where high temperatures are generated in contact, the mechanical properties determined at room temperature may be less relevant than those measured in high-temperature tests. High temperature coating nanomechanical tests can be complemented by nano-tribological tests. These provide severe tests for coatings that simulate high contact pressure sliding/abrasive contacts at elevated temperature. Analytical modelling shows that coating behaviour in the high-temperature test can be explained by temperature-dependent changes to the stress distribution in the highly loaded sliding contact.