We use the salt bath process on numerous different types of SS parts, 17/4, 304, 316, and 303.
You will have a much higher surface hardness than Rc 55.

I have used it for enhancing the wear properties in highly abrasive flow conditions.

I have use it also for treating stainless steel in pumps and rotating process equipment where there is possibility of incidental contact.  

We have found that there is a loss of corrosion resistance in some of our highly oxidizing environments, i.e. HNO3.  I have seen no problems in other environments like steam, water, or any organics

If you could comeback with the end use it might help with the selection of the SS.

 

The parts are part of a small automated mechanism.  This particular part is like a little striking hammer.  I need 55RC in the core to withstand the battering at the nose of this part.  It does not get slammed but undergoes many spring powered strikes.  Melonite on a soft part would soon deform and render the part unusable.

We are currently using 8620 with a .030 case at 60 RC.  This works well but the Melonite will provide better scuffing resistance and make the part more ascetically pleasing with its nice black color (and save us a finishing step)

I would lean toward a PH grade.  They have some corrosion resistance and the temp is in the range for aging to maximum toughness.  The core hardness will only be in the low 30's.

As I think about it I don't know of any grade that you can age or temper at 1075F and end up with 44Rc, except a hot work tool steel like H19.  You wouldn't have much corrosion resistance, but it would be hard as hell.

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Corrosion never sleeps, but it can be managed.
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