What microstructure is
Microstructure is the arrangement of phases and grains inside a metal, visible under a microscope after polishing and etching — it is what sets a part’s hardness, toughness and wear resistance.
In steel, the main phases come from how much carbon it holds and how it is heated and cooled.
The main phases in steel
- Ferrite — iron with little dissolved carbon; soft and ductile.
- Pearlite — alternating layers of ferrite + cementite; medium hardness (shown in the photo).
- Austenite — forms at high temperature (~800–900°C) and dissolves a lot of carbon; the starting point for hardening.
- Martensite — forms on rapid quenching from austenite; very hard but brittle = the source of hardness.
- Bainite — a tough/hard balance, formed at intermediate cooling rates.
Why metallurgy matters for hardening
Hardening transforms the microstructure into martensite, then tempering reduces brittleness — control the phases and you control quality.
Microstructure analysis in the lab confirms real martensite (not false hardness) and checks case depth and surface decarburization.
FAQ
Why look at microstructure?+
To confirm real martensite formed, measure case depth, and find the cause of failures — the heart of heat-treatment QC.
What is the photo in this article?+
A real micrograph of low-carbon steel showing ferrite (light) and pearlite (dark); the scale bar is 100 µm.
Can V.S. Heat Treatment analyze microstructure?+
Yes — our in-house lab checks microstructure, hardness and coating thickness on every lot.
