How does cast iron’s microstructure influence its susceptibility to cracking?

Cast iron’s susceptibility to cracking is heavily influenced by its unique microstructure, which consists of graphite flakes embedded in a pearlite or ferrite matrix. The graphite flakes act as stress concentrators, creating weak points where cracks can initiate and propagate under mechanical or thermal stress. The size, shape, and distribution of these flakes play a critical role—larger or irregularly shaped flakes increase brittleness and crack risk. Additionally, the pearlite matrix, while strong, can become brittle under rapid cooling, further exacerbating cracking tendencies. Thermal cycling or uneven cooling can induce internal stresses, leading to microcracks that grow over time. Understanding these microstructural factors helps in selecting or engineering cast iron for applications where cracking resistance is crucial.