Microstructural Analysis and Tribological Performance of Composite Iron Sulfides in Automotive Brake Pads

Abstract

This research explores the tribological characteristics of brake friction materials, focusing on synthetic iron-based sulfides with unique microstructures. Tribological testing, conducted per the SAE J2522 and SAE J2707 standards across diverse temperatures, reveals the superior performance of brake pads incorporating composite iron sulfide, especially at high temperatures. These pads exhibit stable friction levels and reduced wear compared to those utilizing pure iron sulfide, signifying a noteworthy advancement in overall tribological properties. A comprehensive cross-sectional analysis of friction materials using Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM/EDS) reveals chemical alterations. Pure iron sulfide undergoes extensive oxidation compared to composite iron sulfide, which exhibits oxidation near the friction surface due to differences in the oxidation mechanism because of the differential microstructure. Furthermore, Thermogravimetric Analysis (TGA) and X-ray Diffraction (XRD) techniques were employed to validate the observed differences. The research highlights the pivotal role of microstructure in influencing the kinetics of thermal oxidation. An alternative oxidation mechanism is postulated for composite iron sulfides, offering insights into disparities in oxidation processes compared to pure iron sulfides. A noteworthy aspect is the protective function of magnesium oxide in composite iron sulfide, acting as a shield against oxidation. These findings indicate significant performance enhancements for composite iron sulfide (FE50), particularly in high-temperature conditions, exhibiting consistent friction coefficients and reduced wear compared to pure iron sulfide (FE10).