Influência do desgaste e do calor de frenagem na microestrutura de discos de freio

Abstract

With the increasing improvement of automotive vehicles, it became necessary to improve all the brake systems, following the automotive evolution. Of all the existing systems, disc brake system is the most widely used, consisting of the disc locking the compression applied by tablets, providing braking. Usually these discs are manufactured in gray cast iron because they have good wear resistance, good conductivity and thermal diffusivity, low cost and other advantages, which make this one of the most suitable materials for the production of discs. However, the properties of this material and consequently the drive efficiency is influenced by the morphology, distribution and size of this graphite phase which may change during the steps of the disk fabrication process or during use in automotive vehicles due the heat variations and wear during braking, and the reason for carrying out the work, which aims to determine the degree of influence of heat and wear on the microstructure and properties of gray cast iron brake discs. Thus it was performed the current study, where through the metallographic preparation was possible to analyze the microstructures of samples of the new discs and used, using for this an optical microscope at 100x magnification and 1000X, identifying the graphite phase in the form of shafts, and the predominantly pearlitic matrix. It can be concluded therefore that the discs showed no differences in morphology and type of a graphite, but there was greater dimensioning of graphite flakes disk used than the new record, indicating that the braking heat or the process itself of casting may have influenced the used disk microstructure.