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Hard Coating 4140 and Ductile Cast Iron

Hard Coating 4140 and Ductile Cast Iron

Hard Coating 4140 and Ductile Cast Iron

(OP)
Question:
Is there a coating process where the equipment (to do the coating process) can be bought?  

Situation:
We currently use a QPQ (Molten Salt Bath Nitriding) but we have to ship the parts to the processing plant.  This type of equipment is approximately $500,000 and carries a good amount of EPA baggage.

We would like to have something above 65 Rc with good corrosion properties (versus bare metal).  Additionally, the dimension stability is very tight - we can tolerate almost no part growth whatsoever.  Our tolerances are +/-.0005 on a finished part.  However, if growth is predictable and repeatable - we can adjust for it.

I have experimented with a boronizing treatment - which might still be the solution, but it appears to cause part growth.  The ductile iron, being cast, will move an intolerable amount due to the machining stresses and the high application temperature.

Does anyone know of a comparible coating (like the QPQ) where the equipment could be purchased for on-site processing?

jackboot

RE: Hard Coating 4140 and Ductile Cast Iron

No matter what you do your have EPA and all the equipment is very expensive.  There are several processes that give you the hardness you desire, but again they are expensive to install and operate.  Boronizing is expensive to operate unless they have made improvements in the process.
We also got growth on components that were Boronized.

There is one you may look at:

http://www.hitecmetalgroup.com/nitrotec.htm

This is a gaseous process that may not be as expensive to install and operate and its is supposed to be environmental friendly.  We had some test parts that were done and were ok. Sorry I don’t have the specs.

Your tolerances will scare a lot processors away.  Are you locked in with your materials?  How big are both weight and volume?

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