The analysis of the tribological properties of multiple strengthened nanocomposite of the Cu-Al2O3 system

Abstract

This paper presents the results of examined tribological properties of the multiple strengthened nanocomposite Cu-Al2O3 system. Cu-Al2O3 composite powder was obtained by combination of the thermo-chemical procedure and mechanical alloying, which is a completely new approach to synthesis of these materials. The synthesized powders were cold pressed with 940MPa and sintered in hydrogen atmosphere in temperature range of 725-925oC during 15-120 minutes. The samples were thermomechanically treated in two stages after sintering: cold rolling with the final reduction degree of 30% and annealing at 800oC for 1h in hydrogen atmosphere. Characterization of the sintered, rolled and annealed samples included the microstructural examination by scanning electron microscopy (SEM), the quantitative analysis of the SEM microphotographs and the examination on tribological properties. Tribological examinations have shown that the best wear resistance have the samples after heat treatment. The significant influence on the tribological properties has the effect of multiple strengthening mechanisms. These mechanisms include strengthening of copper matrix achieved by dispersion of fine particles of Al2O3, strengthening by the grain boundaries due of the appearance of nanosized Al2O3 particles and the CuxAlyOz phase, as well as by deformation strengthening and strengthening by annealing. Based on the results of the quantitative analysis and tribological examinations, it can be concluded that apart from these strengthening effects porosity also has a significant influence on the tribological properties, i.e. reduction of the volume share in porosity improves tribological properties.