Image icon  Fe, C 0.07, Mn 2.3 (wt%) steel, carburised at 950°C

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Description: 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 left (surface) and hence a martensitic phase, changing to the lighter shade consisting of mostly ferrite.
Keywords: alloy • carbon • carburisation • iron • metal • steel
Categories: Science approaches > Microstructure
Materials > Metals & alloys > Alloy steels
Processes > Thermal treatments > Quenching
Testing, analysis & experimentation > Metallography
Scale > Micro
Created by: Dr R F Cochrane, Department of Materials, University of Leeds
DoITPoMS, University of Cambridge
Published by: DoITPoMS, University of Cambridge
License: This resource is released under the Creative Commons Attribution Non-Commercial Share Alike license (2.0 UK: England & Wales).
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Date created: 04 September 2002
Date added: 21 August 2009
Resource ID: 1309