What is the Iron Carbide diagram?
Short answer
graph TD
A[Iron–Carbon Diagram] --> B[Phases: Ferrite, Austenite, Cementite]
A --> C[Eutectoid: 0.8% C<br>austenite → pearlite]
A --> D[Eutectic: 4.3% C<br>liquid → austenite + cementite]
A --> E[Pearlite = ferrite + cementite layers]
| Region | Carbon range | Microstructure |
|---|---|---|
| Hypoeutectoid | < 0.8 % | Ferrite + Pearlite |
| Eutectoid | 0.8 % | Pearlite |
| Hypereutectoid | > 0.8 % | Pearlite + Cementite |
| Cast iron | > 4.3 % | Graphite/Cementite in matrix |
- Definition: equilibrium phase diagram for iron–carbon alloys (steel and cast iron)
- Key carbon points: eutectoid at 0.8 % C (pearlite formation), eutectic at 4.3 % C (cast iron)
- Phases: ferrite (BCC), austenite (FCC), cementite (Fe₃C)
- As Second Engineer: explains why hull steel is low-carbon (ductile, weldable) while machinery uses higher-carbon alloys
Full answer
The full answer explains each point step by step, with the regulations and figures behind it and the discussion from other candidates. It is in the MEO Class II section of the Marine One forum, open to members enrolled for the MEO Class II exam.