Surface decarburization at various material numbers

 

Surface decarburization is a loss of carbon in the skin of the material. Favoring factors are high temperatures and larger quantities of oxygen in the atmosphere.
In the following some characteristics for a decarburization are listed :
   1. Increased amount of ferrite
   2. Reduction of the amount at carbides
   3. Lamellar pearlite at annealed hypereutectoid steels
   4. Worse etchenability at higher alloyed steels
   5. Various amounts of the different microstructures
These details have to be understood as a change in proportion to the basic structure. You measure up to an imaginary line after which the carbide distribution or the composition of the microstructure doesn't change any more. Smaller fluctuations, which represent a natural irregularity at the carbon distribution, are not considered.
The links listed below lead you to some examples of different heat treatment conditions at various steel grades. The measured depth of the decarburization are marked in the pictures. The represented surface decarburizations and the measurings have been confirmed in this form, also in the conversation with other metallograher. 0,01 - 0,02 mm have to be described as normal differences in the assessment.

1.3505 spheroidised

1.7139 spheroidised

1.7034 untreated

1.8159 spheroidised

1.4034 spheroidised

1.8159 untreated

1.7035 spheroidised

1.2249 spheroidised

1.8507 quenched and tempered

1.2379 spheroidised

1.7709 spheroidised

1.4718 quenched and tempered

1.2826 spheroidised

1.6582 untreated

1.4006 quenched and tempered

1.2381 spheroidised

1.2210 untreated

1.7039 quenched and tempered

1.2516 spheroidised

1.2210 untreated

 

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