Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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Q.P.Q. Process
Q. I'd like to now more about QPQ, or other similar nitriding / nitrocarburizing + black oxidation process.
Which kind of salt is used in the QPQ process. What kind of cleaning processes have to be used before nitriding and before oxidation. What environmental problems result from using this salt, in particular the quenching one? Is it possible to couple a gas nitriding process to a QPQ but only for the quenching-oxidising process?
Does there exist other similar HT with the same surface finishing (very important is uniformity and real black colour)? Thanks in a advance for any help.
L. Gessi- Opera (MI) Italy
2000
A. Hi L.,
Kolene offers the QPQ process and has put a paper about it on-line on this site.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2000
Multiple threads merged: please forgive chronology errors and repetition 🙂
Q. I have a specification for finishing a 303SS thumb screw which calls out (Melonite Q.P.Q.). Does anyone have any information on this process?
Michael Morrison- Stafford, Texas, USA
2001
A. Hi Michael. The 'Q.P.Q.' part stands for Quench-Polish-Quench. Kolene has an article on line here about the Quench-Polish-Quench process at http:/www.finishing.com/library/qpq.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2001
A. Hello Michael!
Melonite is an olde trademark of Lindberg Heat Treating for their salt bath nitriding, which they now call Lindure. The QPQ process is Kolene's name for their SBN variant (they quench-polish-quench to give better surface properties). So I don't think that there is a Melonite QPQ. (See below)
However, your best bet is to go right to the horses's mouth, at Kolene.
Good luck!
Lee Gearhart
metallurgist - E. Aurora, New York
2001
A. MELONITE QPQ is a trademark of Houghton Durferrit GmbH, Germany. The MELONITE salt bath nitrocarburizing process is available at commercial heat treaters around the world.
Rainer Willing- Valley Forge, Pennsylvania
2001
Multiple threads merged: please forgive chronology errors and repetition 🙂
Advice on QPQ
(2002)
Q. We manufacture a conveyor belt scraper that consists of a mild steel shaft, a piece of mild steel channel, and two tensioners. We are looking into ways we can make the unit more corrosion resistant. Is QPQ a good option? Is it more cost effective than stainless? Should parts be prepared before coating? And, finally, does the coating replace paint?
Shaun Carnes- Highland, New York
(2002)
A. I do not know what QPQ is.
On a practical side, for economic reasons, I personally would not recommend any coatings on a 'consumable surface'. Short of utilising abrasion resistant (and expensive)chromium or ceramic coatings or hard alloys I would recommend designing the scraper to take a quick-fitting sacrificial module on the workface (cheap). This would need to be a harder tool steel with a simple profile for cheap manufacture. Work life would be long and replacement time measured in minutes (Bolt on?). I would possibly recommend avoiding electrochemical corrosion by isolating the module from mild steel components with a nested block of polypropylene.
John Tuohy- Ireland
Ed. note: We have an article on the Kolene QPQ process here at finishing.com/library/qpq.
Effect of QPQ on thread strength
Q. I am a designer of hydraulic manifold blocks in the water hydraulic industry. These blocks have mounted valves, connection ports and cross drills on all surfaces. These manifolds are used in raw water and 95/5 systems with pressures up to 5000 psi. If carbon steel is used the material receives QPQ or gas nitriding treatment after machining. My question is do the threads lose any of their strength after either of these two corrosion resistant processes? Or do the threads increase in strength? I have not been able to find any information on this subject. Have any tests been done?
Chris Marconihydraulic design - St. Catharines, ON, Canada
2004
A. I don't know the answer to your question, but I would highly recommend you talk to Kolene about it. They are the experts on the QPQ process.
Toby PadfieldAutomotive module supplier - Michigan
2004
Need vendor for QPQ or salt bath nitriding in North America for large diameter parts
RFQ: We are looking to locate a vendor who can complete a Salt Bath Nitriding (QPQ, Melonite, Tenifer, etc.) on some large cylindrical parts (the largest is 52" in diameter by 60" in length) In the past we used to hard chrome the parts but we rather do a QPQ process to ensure long life to the part
Thank you
TechShop - San Jose, Costa Rica
2006
Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)
Seeking melonite QPQ process in Far East (China, Taiwan, or Hong Kong)
RFQ: Looking for QPQ / Melonite process for gears in China / Taiwan.
Andrew OlefsonAutoparts - Fort Lauderdale, Florida, USA
2006
Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)
Multiple threads merged: please forgive chronology errors and repetition 🙂
Q. What does QPQ stand for?
don guidrymachine shop - Laf. Louisiana
July 28, 2008
A. Hi, Don. It stands for Quench-Polish-Quench. Please see the article for the details of what it involves.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
July 31, 2008
Q. We need to have full details of the Nitriding bath.
JAGMOHAN Singh- DEHRA DUN, Uttrakhand, India
May 26, 2009
A. Hi, Jagmohan. You would need to contact Kolene or Melonite for their technical data sheets and MSDS, depending on which brand you are interested in. These are proprietary processes and protected by patent and or trade secrets -- they'll give you enough information for your purposes, but they won't provide "full details". Do you want to know the properties of the deposit? Do you want to inquire whether you can license the process for installation in your factory? Are you looking for a licensed applicator?
If you can be a bit more detailed about your own situation, maybe we can refer you to some published info. Thanks.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
May 26, 2009
Q. I am looking into salt bath nitriding for some pivot pins. 100 ksi yield(1144/1045/1050). Looking for good corrosion resistance (250-300 NSS hours). Have been reading about the process but cannot figure out if nitriding messes with the temper or not. Also, do ASTM/SAE specs exist for this type of process? Seems that they are mostly proprietary. Any help is appreciated.
Thanks,
Product Designer - Greencastle, Pennsylvania
December 17, 2009
Q. Is there any buildup on the parts from this process?
Dean Beenken- Bethel, Minnesota USA
March 14, 2013
Permissible to shot blast nitrided surface to prep for blackening?
Q. Hello sir,
My client is having nitrided parts (with white nitride layer formed on top of the surface). Can we do shot/glass bead blasting to remove this layer?
We are facing great difficulty to do blacking on that surface. We tried cleaning with hydrochloric acid, but still the finishing is not acceptable.
- Bangalore, Karnataka, India
September 10, 2016
A. Plating on a nitrided surface is very difficult if not impossible.
If you blast deep enough to achieve easy plating, then you have probably destroyed much of the hard nitrided surface.
Best advise is to use the parts as is or use a different hardening process.
Jeffrey Holmes, CEF
Spartanburg, South Carolina
September 14, 2016
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