Question:
Which sequence correctly orders steel microstructures from highest to lowest hardness?
Which sequence correctly orders steel microstructures from highest to lowest hardness?
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Hardness increases with lattice distortion and decreases with carbide spheroidization.
Updated On: Jun 29, 2026
- Fine pearlite, Martensite, Bainite, Spheroidite
- Martensite, Tempered martensite, Bainite, Spheroidite
- Bainite, Martensite, Fine pearlite, Spheroidite
- Tempered martensite, Fine pearlite, Martensite, Spheroidite
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Verified By Collegedunia
The Correct Option is B
Solution and Explanation
Concept:
The hardness of steel microstructures depends on carbon distribution, lattice distortion, and phase morphology.
In general:
\[
\text{Martensite} > \text{Tempered Martensite} > \text{Bainite} > \text{Pearlite} > \text{Spheroidite}
\]
Step 1: Understand martensite hardness.
Martensite:
• supersaturated solid solution of carbon in BCT iron
• highly distorted lattice
• maximum hardness among steel phases
Step 2: Effect of tempering.
Tempered martensite:
• carbide precipitation reduces stresses
• slightly lower hardness but improved toughness
Step 3: Bainite and spheroidite.
• Bainite → intermediate hardness
• Spheroidite → lowest hardness (softest, most ductile) Final Answer: \[ \boxed{\text{Martensite, Tempered martensite, Bainite, Spheroidite}} \]
Step 1: Understand martensite hardness.
Martensite:
• supersaturated solid solution of carbon in BCT iron
• highly distorted lattice
• maximum hardness among steel phases
Step 2: Effect of tempering.
Tempered martensite:
• carbide precipitation reduces stresses
• slightly lower hardness but improved toughness
Step 3: Bainite and spheroidite.
• Bainite → intermediate hardness
• Spheroidite → lowest hardness (softest, most ductile) Final Answer: \[ \boxed{\text{Martensite, Tempered martensite, Bainite, Spheroidite}} \]
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