White cast iron is characterized by extreme hardness due to rapid cooling.

White cast iron is characterized by extreme hardness due to rapid cooling.

• A. Brittle
• B. Extreme hardness due to rapid cooling
• C. Not wear resistant
• D. High ductility

Answer: (B)

Extreme hardness in white cast iron comes from its microstructure formed when molten iron with high carbon content cools very quickly. The rapid cooling prevents carbon from forming graphite and instead yields hard cementite (iron carbide) and related phases. This cementite-rich combination is extremely hard, giving the material its characteristic hardness and wear resistance, while the lack of graphite makes the metal brittle and low in ductility. So describing white cast iron as extremely hard due to rapid cooling best matches both its observed property and the reason behind it.

Extreme hardness in white cast iron comes from its microstructure formed when molten iron with high carbon content cools very quickly. The rapid cooling prevents carbon from forming graphite and instead yields hard cementite (iron carbide) and related phases. This cementite-rich combination is extremely hard, giving the material its characteristic hardness and wear resistance, while the lack of graphite makes the metal brittle and low in ductility. So describing white cast iron as extremely hard due to rapid cooling best matches both its observed property and the reason behind it.