Assessing Hardening Particles Distribution in Composite Coatings

CerMet coatings for brake discs are emerging as innovative technological solution to limit wear of brake devices and the corresponding emission of particulates into the environment. These coatings are usually composed by a dispersion of hard ceramic particles (Cer) in a metallic matrix (Met). Fine tuning of the ratio between Cer and Met components as well as the homogeneity of dispersion of hard particles into the matrix are pivotal parameters defining physico-mechanical properties of such composite coatings, such as their hardness and wear resistance. This contribution proposes an analytical methodology based on scanning electron microscopy (SEM) and image analysis (IA) to evaluate the distribution of ceramic particles in metal matrix composing CerMet coatings for brake discs. The methodology is demonstrated effective in assessing correlation between such parameters and the hardness of the coating, as measured by instrumented indentation carried out on investigated metallographic sections. In particular, a linear decreasing trend is observed in the hardness of the produced coating when decreasing the Cer to Met ratio, moving from maximum values of 670 HV to minimum values of 350 HV for Cer:Met ratio of respectively 24:76% and 6:94%.