effects of steel fibers and cu powder on wear and friction characteristics of brake pads

Brake pads are critical components in any vehicle's braking system, providing the friction necessary to convert kinetic energy into heat and bring the vehicle to a safe stop. their reliability and performance directly impact the driver's ability to maintain control and prevent accidents, underscoring their paramount importance in road safety. generally, pad friction materials of brake systems are composed of a mixture of ingredients grouped into four material categories: fillers, abrasives, lubricants, and reinforcing. cu has proved to be one of the most important ingredients in brake pads. indeed, it improves the thermal conductivity of brake pads and helps to build up a compact friction layer, in such a way as to avoid the thermal fade and decrease the wear rate of brake pads. although cu has a multifunctional contribution to brake performance, its usage in brake pads has recently become a subject of debate due to its potential toxicity to aquatic species. for this reason, potential alternatives for the production of cu-free brake pads have recently been evaluated.in this study, steel fibers with a particle size range of 300-600 µm were prepared instead of cu powder in proportions of 8, 6, 4, 2, and 0 %. cylindrical samples with a diameter of 25 mm and a height between 8 and 11 mm were produced by the following steps: 1. single ingredient raw powders/fibers and phenolic resin were mixed for 30 min; 2. a cylindrical mold was filled with the achieved mixtures; 3. hot pressing with a uniaxial hydraulic press under 20 mpa pressure and 160℃ temperature for 5 min. 4. hot-pressed samples were initially heat treated for 1 hour at 100°c, followed by 2 hours at 130°c, and finally, 2 hours at 180°c.a pin-on-disk tribometer was used to measure the specific wear rate of the samples by applying a force of 29n at a rotation of 240rpm, based on archard's law. the optimal wear rate was reported based on the isiri 586 standard for samples containing 4% cu and 4% steel fibers with a specific wear rate of 0.8118 ×10^(-6) gr/m . in order to check the actual braking conditions and changes in morphology and material interaction, the wear test was also evaluated at 300℃. the samples containing 2% cu and 6% steel fibers with a specific wear rate 10.153×10^(-6) gr/m had the lowest wear rate. finally, the changes in the friction coefficient of the samples during different heating and fade stages were compared. it was found that samples with a constant and stable friction coefficient of 0.25 to 0.6 have favorable wear properties.