casting alloy for nitriding

[pparent]

We are looking to change our existing alloys for investment casting from 431 stainless steel to 4130 or 17-4 ph. We then saltbath nitride the parts. We want to reach a Rc of around 30-34 Rc to prevent the parts to become too brittle but keep a good wear characteristic.

Which alloy would be the best choice and why?

thanks

p

 

[unclesyd]

Either of your materials will SBN with ease.
SBN or salt bath carbo-nitriding of 17/4 will give you one of the best easily wear surfaces there is. If you use a process like QPQ (Quench Polish Quench) it will enhance most of the properties of either over just QP (Quench Polish).

I would go with the 17/4 as it has been my work horse as far as wearing and galling. I have a sleeve and barrel made from 17/4 and Nitronic 60 that have run over thirty year in split case horizontal injection pump for a waste injection well. I haven't used much SBN 4130. We used a lot of 4130/4140 parts that are gas nitrided in some very severe services with good results.
A word of caution 17/4 doesn't gas nitride very well.

If you could describe your application it will help someone give you a better answer.
It would be nice to know what you are running against.

Here is a pretty good paper on the SBN process.

http://www.burlingtoneng.com/wear_resistance.html

 

[unclesyd]

Forgot to add neither material will be brittle as this process is surface phenomena. The core is unaffected if you temper the 4130 at least at 1000F and the 17/4 at H1150.

 

[TVP]

As unclesyd mentioned, both can be surface hardened using salt bath nitriding. 4130/4140 is frequently nitrided as is 17-4 PH, so it probably comes down to what strength do you want and how much will it cost. 30-34 HRC will be no problem for either alloy. 17-4PH will cost several times what 4130 does.

 

[EdStainless]

and how much corrosion resistance you are looking for. the 17-4 will be similar to your 431, the other is a steel.

If you sue the 17-4 you need to integrate the SBN and the aging treatment. You don't want to use 17-4 that has not been properly heat treated and aged.

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