Question

Which of the following is not the characteristics of a gray cast iron?

• A. Brittle
• B. Breaks preferentially along the graphite flakes
• C. Produce a white fracture surface
• D. Good damping property

Hint:

Gray cast iron fractures with a \textbf{gray surface} due to graphite — unlike white cast iron, which produces a white surface.

Answer 1

The Correct Option is C

Step 1: Properties of Gray Cast Iron
Gray cast iron is a type of cast iron that contains: - Flake graphite in its microstructure, - High carbon content (~3–4%). Key characteristics: - Appears gray due to the graphite flakes, - Brittle, due to stress concentration around flakes, - Has excellent damping properties, - Fractures preferentially along the graphite flakes, - Produces a gray fracture surface, not white. Step 2: Contrast with White Cast Iron
- White cast iron has cementite (Fe\(_3\)C) instead of graphite. - It fractures with a white, shiny surface due to absence of graphite. - Gray cast iron has a dull gray surface when fractured due to presence of graphite flakes. Conclusion: The statement "Produce a white fracture surface" is not true for gray cast iron.