Iron Carbide

Iron carbide, specifically epsilon iron carbide (ε-Fe3C), is commonly known as cementite and is a major constituent in steels and cast irons. Here are the key parameters that define its properties:

  1. Chemical Formula: ε-Fe3C (also written as Fe₃C)
  2. Molecular Weight: Approximately 184.11 g/mol
  3. Appearance: Cementite occurs as a hard, brittle, and lath-like or platelet structure within the microstructure of ferrous alloys.
  4. Density: Around 7.70 g/cm³, which is higher than pure iron (7.87 g/cm³) due to its interstitial carbon atoms.
  5. Formation Temperature: Cementite typically forms during the cooling of iron-carbon alloys from high temperatures, below the eutectoid temperature (approximately 727°C for plain carbon steels).
  6. Hardness: It has a high hardness, typically around 800 Vickers (Hv), which contributes to the overall hardness of steels and cast irons.
  7. Thermal Conductivity: Cementite’s thermal conductivity is lower compared to ferrite or austenite phases in steel, affecting heat treatment behaviors and microstructural transformations.
  8. Chemical Stability: Cementite is stable at room temperature but can decompose into iron and graphite under certain conditions, such as prolonged exposure to high temperatures or in the presence of strong reducing agents.
  9. Magnetic Properties: Cementite is paramagnetic, meaning it shows magnetic properties only when subjected to an external magnetic field.
  10. Corrosion Resistance: Cementite can be susceptible to graphitization in the presence of certain acids, leading to microstructural changes and potentially weakening the material.
  11. Role in Steel and Cast Iron Microstructures: In steels, cementite forms as a constituent of pearlite (an alternating layer of ferrite and cementite), influencing the material’s hardness and toughness. In cast irons, it can exist as a primary phase or in complex eutectic structures, affecting the material’s machinability and wear resistance.

  12. Formation Mechanisms: Cementite forms through a diffusion-controlled process during the cooling of iron-carbon alloys, either by direct precipitation or as part of eutectic or eutectoid reactions.

Iron carbide, specifically epsilon iron carbide (ε-Fe3C), is commonly known as cementite and is a major constituent in steels and cast irons. Here are the key parameters that define its properties:

  1. Chemical Formula: ε-Fe3C (also written as Fe₃C)
  2. Molecular Weight: Approximately 184.11 g/mol
  3. Appearance: Cementite occurs as a hard, brittle, and lath-like or platelet structure within the microstructure of ferrous alloys.
  4. Density: Around 7.70 g/cm³, which is higher than pure iron (7.87 g/cm³) due to its interstitial carbon atoms.
  5. Formation Temperature: Cementite typically forms during the cooling of iron-carbon alloys from high temperatures, below the eutectoid temperature (approximately 727°C for plain carbon steels).
  6. Hardness: It has a high hardness, typically around 800 Vickers (Hv), which contributes to the overall hardness of steels and cast irons.
  7. Thermal Conductivity: Cementite’s thermal conductivity is lower compared to ferrite or austenite phases in steel, affecting heat treatment behaviors and microstructural transformations.
  8. Chemical Stability: Cementite is stable at room temperature but can decompose into iron and graphite under certain conditions, such as prolonged exposure to high temperatures or in the presence of strong reducing agents.
  9. Magnetic Properties: Cementite is paramagnetic, meaning it shows magnetic properties only when subjected to an external magnetic field.
  10. Corrosion Resistance: Cementite can be susceptible to graphitization in the presence of certain acids, leading to microstructural changes and potentially weakening the material.
  11. Role in Steel and Cast Iron Microstructures: In steels, cementite forms as a constituent of pearlite (an alternating layer of ferrite and cementite), influencing the material’s hardness and toughness. In cast irons, it can exist as a primary phase or in complex eutectic structures, affecting the material’s machinability and wear resistance.

  12. Formation Mechanisms: Cementite forms through a diffusion-controlled process during the cooling of iron-carbon alloys, either by direct precipitation or as part of eutectic or eutectoid reactions.

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