Red Mud Ratio Effects on the Tribological Performance of Fly-Ash-Reinforced Bronze Matrix Brake Pad Material

Different amounts of red mud (0%, 2%, 4%, 6%, and 8%) were added to bronze matrix brake pad material reinforced with 12% fly ash and then hot-pressed at 800 degrees C and 40 MPa for 5 min. Wear-friction tests were conducted to determine the friction coefficient and specific wear rate, which are important indicators for evaluating the performance of brake pad samples. For all samples, the hardness and density were determined, fractured surfaces and microstructures were examined, and transverse rupture strength (TRS) was calculated using a three-point bending test. The hardness values of the samples increased with increasing red mud content, and their density values slightly decreased. TRS values of the samples increased with up to 4% red mud addition, but decreased when above 4%, and the friction coefficient of the brake pad samples decreased with an increase in red mud content. Moreover, all samples containing red mud, except the sample containing 2% red mud, showed a lower specific wear rate than the bronze matrix brake pad material reinforced with 12% fly ash. The worn surfaces of the specimens were also examined using scanning electron microscopy (SEM) and a 3D optical profilometer.