Investigation of the effect of refined boron component addition on the microstructure, hardness, and wear properties of brake pads

In this thesis, the effects of adding refined boron compound to brake pads on microstructure, hardness, and wear properties are investigated. The primary materials used in the study include novolac resin, copper, alumina, graphite, brass, zirconium silicate, calcium sulfate, zinc sulfate, and barium sulfate. Additionally, boric acid and borax decahydrate powders are incorporated into the brake pad mixture in specific weight ratios. In the material formulation, barium sulfate was reduced by 1.25%, 2.5%, 5%, 10%, and 20% of the total weight, and boric acid and borax decahydrate powders were added in place. After weighing, all materials were mixed with a mechanical mixer, placed into 30 mm diameter molds, and pressed for 30 seconds under 10 MPa pressure at 140°C. Three samples were produced for each formulation. The microstructures of the produced samples were examined using an optical microscope. Additionally, the theoretical and bulk densities of the samples were calculated, and porosity rates were determined based on these density values. The samples' hardness was determined using the Brinell hardness test, and wear tests were conducted under an 18 N load at 400 m, 800 m, and 1200 m sliding distances. Microstructure analysis revealed that the samples had a porous structure, and it was observed that as the proportion of boron compound in the structure increased, the porosity also increased. This caused a decrease in density. In the samples with refined boron products, hardness values initially increased with the increasing reinforcement ratio, but a decrease in hardness was detected once a certain reinforcement ratio was exceeded. The highest hardness values were obtained at a 2.5% reinforcement ratio for samples with boric acid and at a 5% reinforcement ratio for samples with borax decahydrate. Furthermore, a linear relationship between hardness and wear was observed. It was noted that the samples with the highest hardness had lower wear volume and rate. Additionally, it was also found that the addition of refined boron compound to the brake pad sample increased the friction coefficient.