Thermal Cracking and Friction Performance of Two Kinds of Compacted Graphite Iron Brake Discs under Intensive Braking Conditions

The limited thermal conductivity of compacted graphite iron constrains its application in brake discs. The matrix plays a crucial role in balancing the thermal conductivity and mechanical performance of compacted graphite iron. Therefore, two kinds of compacted graphite brake discs with different ferrite proportions were utilized to investigate their thermal cracking and friction performance under intensive braking conditions based on inertia friction tests. The variations in peak temperature, pressure load and friction coefficient stability were also analyzed. The brake disc with a higher ferrite proportion exhibited a lower peak temperature, attributed to increased thermal conductivity. Moreover, the elevated content of soft ferrite resulted in a greater furrow height on the worn surface, contributing to an increase in friction force and stability. As a result, both the input pressure and mechanical stress decreased. It was observed that the compacted graphite iron brake disc with a higher ferrite proportion exhibited fewer thermal cracks without compromising wear resistance. Furthermore, the results suggest that lowering the disc temperature to 210 °C–250 °C can mitigate fatigue wear and matrix oxidation, hindering the propagation of thermal cracks.