Partial pressure in Nitriding potential

[eagertknow]

I want to know what type of pressure is the partial pressure of gas in Nitriding potential = (pNH3)/(pH2)^3/2.
I mean is it static, dynamic or total pressure.

Also how this pressure can be measured in a nitriding furnace for on line control of Nitriding potential.
Link to references will be appreciated.

 

[kenvlach]

The nitrogen potential is a function of temperature and the initial pressures of NH[sub]3[/sub] and any added H[sub]2[/sub]. After the gases reach thermodynamic equilibrium at a temperature, the nitriding potential at the solid surface in equilibrium with the gas phase is given as:

K[sub]N[/sub] = P[sub]NH[sub]3[/sub][/sub]/P[sub]H[sub]2[/sub][/sub][sup]3/2[/sup]

--- H.J. Grabke, 'Kinerics of Gas-Solid Interactions,' Mater. Sci. Forum, Vol 154, p 69-85 (1994).

A recent, on-line article that may be useful: "Kinetics of Microstructure Evolution during Gaseous Thermochemical Surface Treatment" by Marcel A.J. Somers and Thomas Christiansen, Journal of Phase Equilibria and Diffusion, vol.26, pp. 520-528 (2005).

http://tempo.ipl.dtu.dk/ipl/upload/publ/9081_1.pdf

An article on controlling and measuring nitriding potential (same article, 2 links for luck):

http://www.badgermetal.com/nitriding-control-article/fnc-article-sh/controlling-nh3-dissociation.htm

http://www.industrialheating.com/CDA/Archives/c47cfb4be5cb7010VgnVCM100000f932a8c0____

Note: search the Industrial Heating (magazine) website for more info.

A vendor's process overview:

http://www.kayex.com/lindberg/brochures/Homo Nitriding Pit.pdf