Influence of the Oxidation Mechanisms of Iron Based Sulfides to Improve Brake Pad Wear and Performance

<div class="section abstract"><div class="htmlview paragraph">The stabilization of friction coefficient and reduction of the wear by sulfides are related to their contribution to modify the phenolic resin (PR) decomposition. Synthetic iron sulfide, FeS, has been always seen as a low cost and stable in price alternative to other metal sulfides, but with some drawbacks in terms of high temperature behavior, due to its oxidation mechanism over 400°C. In previous works, it has been demonstrated that sulfide microstructure has an influence on the wear and friction behavior in iron sulfides composite containing tin. This work explores how adjusting the oxidation mechanism of synthetic iron sulfide (IS) leads to a modification of pad tribo-chemistry that contributes to the reduction of the brake pad wear. Two different synthetic materials based on iron sulfide (pure and composite) were compared to understand the oxidation mechanism and chemical interaction with PR. Tribological data have been obtained through SAE standard tests by using dynamometer equipment. Oxidation and tribo-chemistry were studied by scanning electron microscope (SEM), X-ray diffraction (XRD), differential thermal analysis - thermogravimetric analysis (DTA-TGA) and infrared (IR) techniques. The iron sulfide composite (CIS) allows similar friction performance but significantly reduces the wear of the brake pad, and likely the emissions, due to the different oxidation mechanism in comparison to the pure iron sulfide. In particular, metal oxide present in the composite influences the reactivity of metal sulfide and, consequently, the phenolic resin decomposition. With this work it is expected to contribute to better understanding of sulfides behavior in friction material, allowing the community to find new ways to be more sustainable, being London Metal Exchange (LME) independent in their current and future challenges.</div></div>