Coefficient of Friction Measured from Nano- to Macro-Normal Loads on Plasma Sprayed Nanostructured Cermet Coatings

Alumina dispersed FeCuAl-based nanostructured cermet coatings were deposited from nanostructured powders by atmospheric plasma spraying on low carbon steel substrates. Nanostructuring was retained in the deposited coatings which exhibit up to four distinctive phases as revealed by electron microscopy. In this study, the friction behavior of the distinctive phases at nano-normal load scale was investigated alongside their contribution to the overall friction behavior at macro-normal load scale. Friction behavior at nano-normal load scale was investigated by lateral force microscopy, whereas conventional tribometers were used for investigations at micro and macro-normal loads. It appeared that, the friction measured at nano-normal loads on individual phases is dictated by both composition and hardness of the corresponding phases, and thus influences the overall friction behavior of the coatings at macronormal loads. Moreover, the coefficient of friction at macro-normal loads differs from the one at nano-normal loads, and deviates from Amonton's friction law. (C) The Minerals, Metals & Materials Society and ASM International 2013