The Influence of Alloying Elements on Damping Capacity of Nodular Cast Irons for Braking System Components

The brake noise is one of the highest incidences of complaints from OEM’s customers, causing problems such as passenger disappointment and warranty costs. With the improvement of the comfort and soundproofing of the automobile, the brake noise has increased customers’ concerns, making them believe that it is a component defect, although it is fulfilling its functions. One of the factors that can attenuate the vibration in a structure is the increase in its inherent damping capacity. Therefore, a material capable of dissipating energy of vibrations may minimize noise, vibration and harshness problems in the braking system. In this work, an experimental study of mechanical properties, microstructural analysis and damping capacity was carried out on different nodular cast irons with variation of the Co, Si, RE contents. The research goal is the achievement of the best compromise between the mechanical properties required for the braking system parts and their damping capacity. In spite of the damping capacity and tensile strength that were likely to be mutually exclusive, a simultaneous increase in both was registered for samples with high Si content, comprising different additions of RE, and for samples alloyed with Co. These results seem to be associated with solid solution strengthening of a fully ferritic matrix, combined with nodule density increase.