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Partial pressure in Nitriding potential

Partial pressure in Nitriding potential

Partial pressure in Nitriding potential

(OP)
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.

RE: Partial pressure in Nitriding potential

The nitrogen potential is a function of temperature and the initial pressures of NH3 and any added H2.  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:

    KN = PNH3/PH23/2

--- 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%20Nitriding%20Pit.pdf

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