Synthesis and tribological investigation of carbon nanotube, onion-like carbon and nanodiamond reinforced nickel matrix composites

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Carbon nanotubes, onion-like carbon and nanodiamonds are considered as highly promising reinforcement particles for metal matrix composites. This is justified by their outstanding physical properties like high strength, hardness, electrical and thermal conductivity as well as friction and wear reduction. The present proposal deals with the production of carbon-nanoparticle-reinforced nickel matrix composites and their microstructural, chemical and tribological characterisation. This will provide a direct comparison of the different composites concerning their tribological properties under dry friction.The first milestone will be to optimise the powder-metallurgical parameters of the fabrication, best adapted to each reinforcement. A stable and homogeneous particle/solvent dispersion must thus be achieved and analysed. The subsequent composites will be analysed, compared and optimised in terms of density, microstructure, hardness, topography, particle/matrix dispersion and post-sintering structural particle quality.The second objective consists in interpreting and comparing the tribological behaviour of the composites through further characterisation of the produced wear tracks. This involves the microstructure, oxide formation and particle displacement as well as the wear rate and wear mechanisms. Furthermore, particle degradation or even graphitisation will be surveilled. If observed, the load range responsible for the transformation will be of interest. Consequently, the tribological behaviour, as a function of the relative humidity and load, before and after said transformation will bring further clues as to the governing mechanisms.The next step is the prediction of the mean grain size of the nickel matrix as a function of particle type and volume fraction. A consequent and pronounced particle-matrix pinning effect correlates particle and grain size. For this purpose, the Zener equation will be adapted using experimental microstructural characterisation to fit the corresponding nickel matrix composite. Thus, a direct correlation between the mean grain size and the wear behaviour of the composites will be possible.The present objectives achieved, the most fitting particle can be favoured for tribological applications in nickel matrix composites. The presented study could be the starting grounds for further scientific work in this field using other matrix materials, since, to the best of our knowledge, no such publication compares the tribological properties of different carbon nanoparticles as reinforcement phases in the same metal system.