Nitride networks

per the ams 2759/6 para 3.7 & 3.7.1

we have a job that the parent material is ams 6487 (h-11 tool steel) that requires core hardness of Rc 38-46
case depth of .011-.020 per ams 2759/6...
case hardness of R15n 92 min

these are ext splines by the way.....

#1) what causes nitride networks during nitride..

#2) when is difinable as a nitride network

#3) is it reworkable to remove the nitride network..

 

[metman]

1) I don't really know the answer but will guess it could come from:
a) excess Nitrogen pressure.
b) excess time at primary nitriding temperature and/or if there is a secondary nitriding temperature, which some nitriding processes include, and if this temperature is between the upper and lower critical temperatures. Since this intermediate temperature can cause carbide networks, I suspect the same phenomena might apply to nitride networks.

2) When individual Nitrides agglomerate or join to the extent that there is a discernable spiderweb like microscopic structure. At least this is true for carbide networks so I am guessing again.

3) Again guessing but likely it is reworkable. If you take it to a high enough temperature the nitrides will tend to diffuse and break up. However, this diffusion could cause excessive case depth and since nitrided case is very brittle this could be a problem depending on the application.