In grey cast iron, carbon is present in the form of flakes.

Explanation:
Grey cast iron is a type of cast iron that contains graphite flakes. These flakes are formed during the solidification process of the iron. The presence of these graphite flakes gives grey cast iron its characteristic grey color and unique properties.

Formation of graphite flakes:
During the solidification of grey cast iron, the carbon present in the iron forms graphite flakes rather than remaining in the form of cementite or pearlite. This is due to the specific conditions under which grey cast iron is cast.

Graphitization:
The formation of graphite flakes in grey cast iron is a result of a process called graphitization. Graphitization occurs when the carbon atoms in the iron rearrange themselves into a graphite structure. This process is favored by the slow cooling rate of the iron during solidification.

Flakes vs. other forms:
The presence of graphite flakes in grey cast iron gives it unique properties compared to other forms of cast iron. These flakes act as a lubricant between the metal grains, providing excellent machinability and wear resistance. They also contribute to the damping properties of grey cast iron, making it suitable for applications that require vibration absorption.

Applications of grey cast iron:
Grey cast iron is widely used in various industries due to its desirable properties. Some common applications include engine blocks, pipes, fittings, automotive components, and cookware.

Conclusion:
In grey cast iron, carbon is present in the form of flakes. These graphite flakes give grey cast iron its characteristic properties and make it suitable for a wide range of applications.