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neets (Materials) (OP)
24 May 02 2:01
Hi all,
i want to know various methods of nitrocarburising on SAE 4140 with the required compound zone of 10 -20 microns.

What is the possibility of achieving the compound zone.

What are the factors effecting distortion?

Does the profile of component matter?

how much porosity can be expected?

What process should be followed?
atad (Aerospace)
3 May 03 9:04
I don't know if this is of any help, but there is a couple of similar processes known as Nitrotec and QPQ.

They are similar to carburizing but offer considerable corrosion resistance without any distortion of the component because the process temperature remains below the upper critical temperture of the steel - typically 525°C.
Tribman (Mechanical)
3 Dec 03 11:21
And other process superior to QPQ is the Arcor process. Both are salt bath process but the Arcor achieve a thicker white layer with less porosity. You should achieve 15-18µ of layer.
kenvlach (Materials)
13 Dec 03 22:06
You can get more info by posting in the Metal and Metallurgy engineering, Forum330.
A keyword search for Nitrocarburizing gives 10 threads:
http://www.eng-tips.com/search.cfm?searchstring=nitroca...

Info I posted in 2 additional threads which may be useful.  Note that Kolsterising® isn’t nitrocarburizing, but rather, a relatively low-T carburizing.

From How to increase 304 SS hardness
Thread330-49696:

“Bodycote (http://www.bodycote.com/) has a relatively new Kolsterising® process for case hardening austenitic SS without loss of corrosion resistance.  Similar or identical to i/the process TEV described.
“Wherever components are subjected to severe wear and corrosion attack.”  Also useful for duplex SS & some nickel-based alloys (best corrosion resistance is for ferrite-free alloys containing some molybdenum).  

"Kolsterising is a case-hardening process primarily for austenitic stainless steels. Wear resistance and resistance to galling is improved, while corrosion resistance remains unchanged.

The process involves diffusion of carbon into the work piece surface without the formation of chromium carbides. Post treatment surface hardness is equivalent to between 70 and 74 HRc. Standard case depths offered are 22 or 33 microns."

No change in dimension, so the treatment could easily be used for existing product lines.  It also eliminates the galling problem of SS, so sounds like a winner.”

From Tuftride treatment
Thread330-63253 {link doesn’t work, but I save my posts!}
“The Tufftride® (also known as Melonite® and Tenifer®) nitrocarburizing process belongs to HEF Durferrit, a German company.  The English version of their website is at http://www.durferrit.com/englisch/index.html
About the only info on this site is that “This nitrocarburizing process has undergone continuous development with regard to its regenerability and ecology,” i.e., control parameters may have changed.
    
The most informative site I found is http://www.keighleylabs.co.uk/keighleylabs/HeatTreatmen...

Another site with descriptions of the various Tufftride® processes is at http://www.bowmic.com/bowmic/tufftride.asp

Description of both the Tufftride® process and the Melonite® variation are at http://www.trutecind.com/heat/tuff.htm

Hope this helps,
Ken

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