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Nitriding steel

  1. Nov 4, 2003 #1
    Hallo erstmal.

    I would like to know how nitriding steel works, how it hardens steel, whether it makes it more brittle and basically everything else that is interesting about it.

    also, I was wondering whether carbon migration has a similar effect, and whether the carbon forms a compound with the iron, and what is the maximum percentage of carbon you can have in steel...

    is it true that in ancient greece (or was it rome) people heated swords and slashed up their prisoners to harden the blades, or is that just a myth??

    answers please.
    thank you.
    cucumber.
     
  2. jcsd
  3. Nov 7, 2003 #2
    Nitriding involves ntrogen diffusing into the surface of certain steels and forming compounds. It then deforms the steel structure at the surface putting the atomic bonds into tension. This makes the surface very hard indeed (you can't touch it with a hacksaw) and also improves the fatigue strength massively. Fatigue occurs when a cycle of tension, then compression continues for a long period of time. By putting the bonds into tension all the time, the compression part of a wear cycle reduces the tension and then increases it, but doesn't actually put it into compression any more - ie there is no longer a compression/tension cycle, so fatigue problems reduce massively.

    It doesn't make the object brittle, as the process only involves the surface and the main material is free to flex as before.

    I've had my BSA motorcycle crankshaft nitrided and it hasn't shown any wear at all in thousands of miles of use!

    The story about the Romans is believed to be true but the effect would be minimal - if any at all.


    Carbon percentages can go to quite high values but as it goes up, the steel becomes very brittle and unusable.

    Carbon atoms help to pin down dislocations in the steel and so reduce the steels ductility. Carburizing is a surface effect that gives a very hard surface.
     
  4. Jan 21, 2011 #3
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