White iron is extremely hard and brittle. The answer lies in its microstructure. The microstructure consists of a thick continuous network of carbides embedded in the Pearlitic or martensitic matrix. This carbide network is extremely hard and resists any plastic deformation. This is the main reason for white cast iron to be hard and brittle. When crack generates within carbide network, crack flows immediately and no other micro cracks are generated. That’s why the surface of fractured white cast iron appears white.