Microstructure, mechanical properties and tribological behavior of Cu-nano TiO2-MWCNTs composite sintered materials

Abstract

The paper presents the results of microstructure, mechanical and tribological tests of copper matrix sinters with the addition of nano-TiO2 and copper-decorated multi-walled carbon nanotubes. A powder metallurgy was used for the production of composite materials. The aim of the work was to determine the properties and wear mechanism of the produced sinters with single additives and to investigate the synergistic interaction of titanium dioxide and carbon nanotubes. Wear tests were carried out using the pin-on-disc method at room temperature and 600 °C. Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Raman Microscopy, Thermogravimetric Analysis (TGA), Dilatometry (DIL), X-Ray Diffraction (XRD), and profilometer were used for the research. Moreover, the stiffness and hardness of the sinters were examined. The main wear mechanisms of the friction pairs tested at room temperature and 600 °C were adhesive, abrasive, and oxidation wear. Furthermore, at the test temperature of 600 °C, the formation of a tribofilm was observed on the surface of the friction pairs, which reduced friction wear. The introduced additions to the copper matrix increased its hardness, stiffness, work of axial deformation, and wear resistance. Moreover, additions decreased the relative value of the thermal expansion coefficient of the sintered copper. The friction pair no. 2 (Cu + 1 wt % MWCNTs – Inconel®625) was characterized by the lowest coefficient of friction at room temperature and 600 °C, of approximately 0.62 and 0.56, respectively. The sintered composite material of Cu – 10 wt% nano TiO2 – 1 wt%. MWCNTs was characterized by the highest mechanical properties and the lowest wear.