Cast iron classification — white iron characteristics: Which statements correctly describe white cast iron?

Introduction / Context:
White cast iron is a cast iron in which carbon exists predominantly as cementite (iron carbide) rather than as free graphite. This microstructure confers specific mechanical and machining characteristics that distinguish it from grey and ductile irons.

Given Data / Assumptions:

• Rapid cooling or appropriate composition suppresses graphite formation.
• Microstructure: ledeburite and cementite networks with little to no free graphite.
• Mechanical behavior considered under static loading.

Concept / Approach:
Cementite is extremely hard and brittle. Consequently, white iron exhibits very high hardness and compressive strength but poor tensile strength and virtually no ductility. Its lack of graphite makes it difficult to machine. These features make white iron suitable for abrasion-resistant applications such as liners and wear plates, but unsuitable where tensile loads or machining are dominant considerations.

Step-by-Step Solution:
Identify carbon state: present as carbide rather than graphite → white fracture surface.Infer mechanical properties: hard and brittle → low tensile strength, high compressive strength.Compare to grey iron: grey iron has graphite flakes that aid machinability; white iron does not.Therefore, all listed statements (a), (b), and (c) correctly describe white cast iron.

Verification / Alternative check:
Metallography reveals cementite networks; hardness tests show high values; machining is extremely difficult without special tooling.

Why Other Options Are Wrong:
Option (e) describes grey cast iron where graphite flakes improve machinability and damping; it does not apply to white iron.

Common Pitfalls:
Confusing white iron with malleable iron (which is produced by heat-treating white iron to convert carbides to temper carbon nodules) or assuming all cast irons machine easily.

Final Answer:
all of these