ZrB₂-Copper-Graphite Composite for Electric Brushes: Positive Effect of ZrB₂ Addition on Composite Properties

A ZrB₂-copper-graphite composite was produced through powder metallurgy and was tested as a new electric brush material. The aim of this paper was to study the effect of ZrB₂ addition on the composite's properties. Besides its physical properties such as density and resistivity, its mechanical properties, such as hardness, bending strength and wear resistance, were studied. A scanning electron microscope (SEM) was used to study the morphology of the wear surface, and a configured energy-dispersive spectrometer (EDS) was used to research the chemical composition of the samples. The results showed that, with the addition of ZrB₂, the composite's properties such as density, resistivity, hardness, and bending strength improved significantly. Compared with samples without ZrB₂, samples with the addition of 4% ZrB₂ achieved a hardness of 87.5 HRA, which was improved by 45.8%, and a bending strength of 53.1 MPa, which was increased by nearly 50.0%. Composites with 1% content of ZrB₂ showed the best wear resistance under non-conductive friction; however, under conductive friction, composites with 4% content of ZrB₂ showed better wear resistance.