Tribological properties of single (AlSi7/SiC_p, AlSi7/GC_sf) and hybrid (AlSi7/SiC_p + GC_sf) composite layers formed in sleeves via centrifugal casting

When designing the composition and structure of a composite material intended for tribological cooperation, many external and structural factors must be considered. The aim of this research was to compare the tribological properties (wear resistance and friction coefficient) of AlSi7Mg1Sr0.03/SiC_p and AlSi7Mg1Sr0.03/GC_sf single-reinforced composite layers with AlSi7Mg1Sr0.03/SiC_p + GC_sf hybrid composite layer formed in sleeves via vertical centrifugal casting. Profilometry enabled quantitative and qualitative analyses to be performed on the wear traces formed on investigated surfaces. The results show that a hybrid composite layer containing spherical glassy carbon particles had a significantly lower and more stable coefficient of friction (μ) and a higher wear resistance compared with single composite layers. The obtained effect was related to the mechanism of vitreous carbon consumption, which was crushed during operation, and then introduced between the cooperating friction surfaces. In this way, it acted as a solid lubricant, which stabilized the coefficient of friction and reduced the wear process.