Friction instability induced by iron and iron oxides on friction material surface

• Published in: Wear Vol. 400-401; pp. 93 - 99
• Main Authors: Noh, H.J., Jang, H.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15-04-2018; Elsevier Science Ltd
• Subjects: Adhesion; Amplitudes; Brake disks; Brakes; Coefficient of friction; Contact pressure; Friction; Friction instability; Gray iron; Hematite; Interface stability; Iron oxide; Iron oxides; Organic chemistry; Sliding; Slip; Surface energy; Surface stability; Vibration; Wear; Wear particles; Gray iron; Iron oxide; Friction instability; Adhesion; Surface energy
• ISSN: 0043-1648; 1873-2577
• DOI: 10.1016/j.wear.2017.12.025

This study analyzed the effect of ferrous wear particles, which can be transferred from gray iron brake discs to the friction material surface during brake applications, on friction instability. To simulate the chemical change of the sliding surfaces, ferrous particles, such as pure iron, Fe2O3, and Fe3O4 particles, were embedded on the sliding surface of a friction material, and their friction characteristics were investigated using a scale dynamometer. The results showed that the ferrous particles aggravated friction instability, showing larger stick-slip amplitudes and wider velocity ranges for friction instability than the bare specimen. The embedded ferrous particles increased the static coefficient of friction and produced larger stick-slip amplitudes in the order of Fe2O3, iron, and Fe3O4, while the friction material without ferrous particles showed the least instability. The surface energy and amount of high-pressure contact plateaus on the sliding surface were attributed to the high friction instability caused by the interfacial adhesion increased by ferrous particles at the sliding interface. This explained the frequent friction-induced noise and vibrations found with a corroded or relatively soft gray iron disc.
•Ferrous particles on the friction material surface aggravates friction instability.•Stick-slip is prominent when ferrous particles are present on the sliding surface.•High surface energy increases interfacial adhesion and static friction.•Brake noise can be affected by the ferrous particles on the sliding interface.