Yayınlarımız

Friction and wear characteristics of materials used in automotive/train brake systems playimportant roles for efficient and safe brake performance. Using single material has never been sufficient to satisfy performance requirements related to wear resistance, so commercial brake pad materials contain many kinds of ingredients [1-3]. Thus, this study aimed to examine the effect of hexagonal boron nitride (h-BN) on the friction characteristics and material properties of non-asbestos composite brake pad containing binder resin, reinforcing fibers, solid lubricants, space fillers and friction modifier. Seven different wt.% combinations of graphite and h-BN were analyzed and the total amount of these solid lubricants in the brake pad was taken as 7 wt.%. While the wt.% of graphite was ranged between 7% and 4% (namely 7%, 6.5%, 6.0%, 5.5%, 5.0%, 4.5% and 4.0%), the h-BN was added in the range of 0% - 3% (0% (XBN-0), 0.5% (XBN- 0.5), 1.0% (XBN-1.0), 1.5% (XBN-1.5), 2.0% (XBN-2.0), 2.5% (XBN-2.5) and 3.0% (XBN-3.0)). Other ingredients of the initial sample were not changed. Mixtures with different compositions were prepared using a small-scale mixer, and a suitable amount of mixture was put into a mold having heating system. The mixture was then hot pressed into that mold and sintered at 200 ºC for 20 min. After these steps, cylindrical composite samples with 20 mm diameter and 15 mm length were produced for subsequent tests. The friction and wear tests were performed using a pin-on-disc type friction material test machine (Brake Pad Friction Tester) developed to test the brake pad materials in accordance with the NF F 11-292 French standard. A 55 mm diameter brake disc made of AISI 52100 bearing steel and having hardness and surface roughness of HRC 55-58 and 0.05 mm, respectively, was used in these tests. The weight loss in wear testswas measured using a microbalance with an accuracy of 0.1 mg. Experiments were carried out under 8 0 N load and at a sliding speed of 26 m.s-1 (2800 rpm). The load was applied and released to the sample holder for 20 s and 150 s, respectively, for 25 cycles.