Title

MAGNETITE FORMATION OBSERVED WITH TEM ON BRAKE DISCS

MAGNETITE FORMATION OBSERVED WITH TEM ON BRAKE DISCS

Authorship

Hinrichs, Ruth; Vasconcellos, Marcos Antonio Zen; Oesterle, Werner; Prietzel, Claudia

Hinrichs, Ruth

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Vasconcellos, Marcos Antonio Zen

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Oesterle, Werner

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Prietzel, Claudia

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DOI

10.5151/2594-5327-33497

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Abstract

The most common brakes utilized in automotive braking are polymer matrix composite (PMC) pads that are rubbed against cast iron discs. During the braking process reactions take place and the new phases, mixed with wear debris, adhere to the surfaces forming a third body. Brakes tested with an AK-Master protocol developed a magnetite layer between the interacting surfaces. Disc samples that reached high temperatures (650°C) in the test procedure were prepared with Focused Ion Beam (FIB). Energy Filtered Transmission Electron Microscopy (EFTEM) results revealed that magnetite was formed on the interface next to graphite flakes in the cast iron disc. TEM captured the detachment of nanometer sized iron particles from the matrix due to the wedging in of graphite layers. Nano- sized cracks between particles allowed the access of oxygen and the formation of magnetite. The graphite from the disc was amorphized during the process.

The most common brakes utilized in automotive braking are polymer matrix composite (PMC) pads that are rubbed against cast iron discs. During the braking process reactions take place and the new phases, mixed with wear debris, adhere to the surfaces forming a third body. Brakes tested with an AK-Master protocol developed a magnetite layer between the interacting surfaces. Disc samples that reached high temperatures (650°C) in the test procedure were prepared with Focused Ion Beam (FIB). Energy Filtered Transmission Electron Microscopy (EFTEM) results revealed that magnetite was formed on the interface next to graphite flakes in the cast iron disc. TEM captured the detachment of nanometer sized iron particles from the matrix due to the wedging in of graphite layers. Nano- sized cracks between particles allowed the access of oxygen and the formation of magnetite. The graphite from the disc was amorphized during the process.

Keywords

Tribology, polymer matrix composite, magnetite

Tribology, polymer matrix composite, magnetite