Characterization and surface properties of copper-free commercial brake pads

This study focuses on the characterization and compositional analysis of a copper-containing commercial brake pad (Kr-ref) manufactured in South Korea. A sample was extracted for detailed investigation, and a pearlitic gray cast iron disc was used as the counter material in tribological tests. Characterization techniques included Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDXS), and X-ray Diffraction (XRD). XRD analysis revealed a complex mixture of crystalline phases, including barium sulfate, calcium carbonate, graphite, brass, vermiculite, magnesium oxide, and others. Due to the limitations of conventional XRD methods in analyzing friction materials (FM), Image J software was used to estimate phase proportions. Graphite and brass were found to be ۱۲ wt% and ۶ wt%, respectively. Phenolic resin was selected as the binder at ۱۰ wt%, with ۳ wt% NBR added to improve elasticity and reduce brittleness. Carbon fibers were limited to ۱ wt% due to their abrasive nature. Magnesium oxide (۳ wt%) and vermiculite (۷ wt%) were incorporated to stabilize friction and suppress noise. Barium sulfate (۲۰ wt%) and calcium carbonate (۱۵ wt%) were used as fillers to enhance thermal and tribological performance. Molybdenum sulfide and potassium titanate, despite their beneficial properties, were excluded due to cost and availability. The study provides a comprehensive framework for designing copper-free brake pads with balanced mechanical, thermal, and tribological properties suitable for commercial applications.