Effect of nitriding on nickel alloys. 1

[knobhead]

I have a piece of maraged steel welded to a piece of nickel alloy (nimocast 718).
After the welding, the assy will be nitrided.
What I need to know, and what seems to be driving our metalugist mental, is what effect (if any) will the nitriding process have on the nickel?
The reason I ask, is we will need to do some machining on the nickel part of the assy following the heat treatment. I would like to turn it, but I don't know if that would be the best choice, given the nitriding. We could grind of course, but that would require us buying some more tooling.
Anyone know?

 

[WKTaylor]

knobhead...

You are nitriding a Nickle Alloy??? Is this REALLY a steel with a nickle constituant???

Every reference I have for nitriding confines the topic to specific STEEL alloys. I think I understand Your metallurgist's "issues" with this situation!

The steel welded to the nickle alloy [Inconel 718?] is a very strange combination. I suggest that the weld-bead will see transition ferrous-nickle alloy elements... and the metallurgy of the weld is going to be a bit strange [may be unpredictable]. I tend to believe that the affects of nitriding should be confined ONLY to the steel and the weld-bead [fusion zone]. What good or bad this nitriding [and weld-material combination] accomplishes may require EXTENSIVE testing [physical, mechanical, environmental]!!!! Regards, Wil Taylor

 

[Hush]

Related Question

Are there any rough guidelines on what materials will take a nitride treatment? I've never tried nitriding alloys 718 or 925, I just assumed it wouldn't work. I know 17-4PH nitrides extremely well but 410 wont take a nitride worth a darn. Do you require a minimum Fe content or is there more to it than that?

 

[knobhead]

Heh, don't blame me, this is the customers idea! The nitriding is only to harden the maraged steel,(which is horrbile enough material) but there is NO masking on the nickel. They've (the customer) has been doing this in-house for ages with no problems, but they grind the part following nitriding and we want to turn it. They don't know what effect nitriding has either (rather worrying for a critical component in a jet engine, but there y'go) The welding is electron-beam welding, and we've got test pieces galore to make sure this is ok, but I agree: the metallurgy in the weld area is going to be...unusual.
The material is nickle base alloy, and is basically the same as the material given by British Standard HC209 with some additional requirements. Our metalurgist has been through the elements that make up the material, and he is of the opinion that nitriding wil probably have no effect. But he can't be sure.
Hmm, I think we're just gonna have to try it, aren't we!

 

CAN I TO USE NITRIDE LAYER IN MARAGING STEEL TO ARMOR APPLICATION ??

 

[bilge]

718 is an extremely complicated alloy and contains a number of elements that form carbides and nitro carbides.

Your metallurgist might be interested in a TTT diagram for the alloy. See: A. Lingenfelter, "Welding of Inconel Alloy 718: A historical Overview," in Superalloy 718 - Metallurgy and Applications, Edited by E.A. Loria, TMS (Warrendale, PA; 1989).

 

[yates]

Yes, nitriding can be carried out on Ni-base alloys. I have experience with ion nitriding an Inconel 718 fastener for an aerospace application.The process is very slow and may require up to 12-15 hours to get .0002 case thickness. So I may suggest that if your nitriding is intended for the steel portion, the relatively short times involved will probably not affect the 718, which removes the need for masking. You will have a lot of difficulty turning the nitrided 718, grinding is the best solution, since it will break through the (very thin - see above) hard case much better.

 

[knobhead]

Excellent! Thankyou very much. Unfortunatly, since I made that post I've been made redundant (9/11 fallout :-()so it's not my problem any more, but I was still wondering.

(I've got another job now.) Excessive accuaracy is a sign of poor breeding. -Socrates.

 

[Maerials]

Please help!
Is there any possibility that the nitriding process can be done in the gear surface?
Thanks a lot!