The effects of natural aging, stress relief & ferritic nitrocarburizing treatment on the damping development of ventilated grey cast iron brake discs

Abstract

This report investigates the change in Q-factor that ventilated grey cast iron brake discs with different treatments applied experience over time to analyse the impact of natural aging, stress relief treatment and ferritic nitrocarburizing treatment (FNC). Eighty grey cast iron brake discs in groups of twenty, each group having a different combination of material treatments applied to them, were measured with a standard damping measuring tool equipped with an excitation hammer and a microphone. Coupled with a microstructural analysis, thorough literally review and additional analysis, in-depth conclusions have been made regarding natural aging, stress relief treatment and ferritic nitrocarburizing treatment (FNC), and much more. The results show that stress relief treatment and ferritic nitrocarburizing treatment (FNC) have significant initial negative effects on the Q-factor, however they are also perceivably self-repairing this initial damage over time. The rate of self-repair is considerably slow, not being close to fully undoing the initial damage after 82 days but considering that the self-repairing trend shows no signs of stopping in its tracks there is a real possibility that it will give time. Other results include natural aging improving the Q-factor over time, geometric design having an impact on the Q-factor of the point measured and ferritic nitrocarburizing treatment (FNC) increasing the hardness of the grey cast iron material.