tapered case depth, carburization vs induction hardening

[lfw618]

Hello, I am a mechanical engineer, could use some input on metallurgical capabilities.

I have a round part that has diameters from 3/4", which are critical, down to less than 1/2". I need a deep case, around .06" on the critical diameters. I am looking to case harden, probably either carburize or induction harden.
I would like to have the deep .06" case on the critical diameters, but shallower (down to around .015"-.03") on the smaller diameters, to help avoid cracking concerns. Would either carburization or induction hardening be a suitable process to create this variable case depth?

Material would most likely be 8620 for carburization or 1038 for induction hardening.

(~60 hrc for the surface hardness, ~50 hrc for effective case depth if that makes a difference)

thank you in advance!

 

[Tmoose]

I'm no metallurgist, but there is not much carbon (.17-.23% ?)in 8620 until it is carburized, so I'm thinking 8620 out of the box probably won't respond much to induction hardening.

 

[AidanMc]

Related, I'm not sure that you'll be able to get to 60 HRC with a 1038 steel...

 

[lfw618]

Tmoose, yea I meant to say that 8620 would be the intended material if carburization would work, and that we would use 1038 if induction hardening were to be used.

AidanMc, OK, that would be an issue. Do you think you might still be able to control case depth depending on location, even if you may not be able to achieve 60 hrc with 1038?

 

[Maui]

You could do it, but it would have to go through the carburizing operation twice. In the first run through carburizing, the areas where you would want to have the shallow case depth would need to be copper plated in order to prevent them from absorbing carbon. And you would have to aim for an effective case depth in the deeper case areas that is slightly below your aim of 0.060". Then strip the copper off, and then re-copper plate the parts but this time plate them in the areas that have already been case carburized to a depth of slightly less than 0.060". Run through the carburizing operation a second time using an aim value of 0.015" - 0.030". It should work if done correctly. We have done it here successfully, but don't like doing it. It takes a lot of time and effort, and ties up our operation when we could be doing things that are more productive. For these reasons, you can expect to pay a premium for someone to carburize these parts for you.

Maui

 

[dbooker630]

If you want to use a medium carbon steel like 1038 or 1045, you should look for material with Manganese at least 0.80% so it can respond well to induction hardening without needing high power and avoiding grain growth.