White Cast Iron: Properties, Applications, and Characteristics

White cast iron is a type of cast iron known for its hard and brittle nature due to the presence of iron carbide (cementite) in its microstructure. Unlike other forms of cast iron, such as gray or ductile iron, white cast iron lacks free graphite, which makes it exceptionally hard and wear-resistant but also more brittle and less machinable.

Composition and Microstructure

White cast iron typically contains 1.8% to 3.6% carbon and 0.5% to 1.9% silicon, along with other alloying elements such as manganese, chromium, and molybdenum. The relatively low silicon content prevents the formation of graphite, leading to a microstructure dominated by cementite (Fe₃C) and pearlite or martensite, depending on the cooling rate and alloy content.

When molten iron solidifies rapidly, carbon in the alloy combines with iron to form iron carbide instead of precipitating as graphite. This results in a hard and brittle structure that gives white cast iron its distinct properties.

Mechanical Properties

• Hardness: White cast iron is extremely hard, typically ranging from 350 to 600 Brinell Hardness Number (BHN), depending on its composition and heat treatment.

• Brittleness: Due to the high concentration of cementite, it is brittle and prone to cracking under impact loads.

• Wear Resistance: The hardness of iron carbide makes white cast iron highly resistant to wear and abrasion, making it ideal for applications where surface wear is a concern.

• Low Toughness: The brittle nature of white cast iron means it has poor impact resistance and is not suitable for applications that require high toughness or ductility.