*2.1. Experiment Materials*

The cast iron used in the experiment was cut from the brake drum of a heavy truck provided by the First AutomotiveWork shop Group in China. The cast iron brand of the brake drum production was HT250, and the structure of cast iron material is shown in Figure 1. The graphite type contained a small amount of type B flake graphite (see Figure 1a); the matrix structure was pearlite (more than 90%) + a small amount of ferrite (see Figure 1b,c); and the main chemical composition is shown in Table 1.

**Figure 1.** Microstructure of cast iron material. (**a**) Graphite structure with cast iron. (**b**) Matrix structure of matched cast iron. (**c**) Pearlite structure amplification with cast iron.

**Table 1.** Chemical compositions of nodular cast iron.


The wear pair selected for this test was a pair of brake pads commonly used in the brake drum of heavy trucks—semi-metallic brake pads—as shown in Figure 2

**Figure 2.** Semi-metallic brake pads.
