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Micrograph 289 and full record

Link to image file for micrograph 289
Micrograph no
289
Brief description
Fe, C 0.15 (wt%) steel, carburised
Keywords
alloy Link to MATTER Glossary entry for alloy, carbon, carburisation Link to MATTER Glossary entry for carburisation, iron, metal, steel Link to MATTER Glossary entry for steel
Categories
Metal or alloy
System
Fe-C-X   Link to phase diagram
Composition
Fe, C 0.15 (wt%)
Standard codes
Reaction
Processing
Case hardened
Applications
Sample preparation
Nital
Technique
Reflected light microscopy
Length bar
800 μm
Further information
After initial casting of this steel it was subject to a process known as carburisation. The metal is heated to above the ferrite-austenite transition in a carbon atmosphere. This establishes a concentration gradient and hence carbon diffuses into the steel. Usually the steel is then hardened by quenching. This produces what is known as a case hardened steel - with a hard surface (case) surrounding a tough core. The carbon gradient can be seen in the changing shade of the sample from left to right, with high carbon concentration at the right (surface) and hence a martensitic phase, changing to the lighter shade consisting of mostly ferrite.
Contributor
Dr R F Cochrane
Organisation
Department of Materials, University of Leeds
Date
04/09/02
Licence for re-use
Attribution-NonCommercial-ShareAlike 4.0 International
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