I doubt very seriously that you will get any kind of satisfactory reponse to that question in here. First of all you have not provided near enough info. What is the temp? What is the flow of the medium? What is the particulate matter (if there is any)causing the erosion? What is the media? How long do you wish to make this thing last?
Secondly, this is a design decision and well beyond the expertise or particular knowledge of anyone here.
Its tough enough making material decisions pertaining to corrosion given the vast and particular services out there, most with little or no public data, but erosion adds to this complication.
If you have no precedence it will end with an educated (or not) guess and by golly.
I would suggest contacting one of the manufacturers of such materials such a Cor-Met and provide them with as much info as you can give.

Hey Madibaa,

Here's some cladding material for 17-4 PH stainless...

http://www.conformaclad.com/upload/File/KMT-3333%20Cladding%20Formulas.pdf

http://www.conformaclad.com/docs/Bulletins/TechBulletins/OF-003.pdf

Now with respect to the process to use, well that depends on the application service conditions, etc. So you need to give us much more info than what you have given us so far, and I'm disappointed in you because, you should know by now that you must give us as many details involved as you can in order for us to assist you an a concise manner. ;)

When you give us such vague information and too little details of it as well, it just makes it more difficult for any of us to understand you specific need and after all, we're NOT mind readers... So tell us as much as possible regarding your project! ;)

Respectfully,
Henry

This may not apply to your situation, yet it is an interesting read nonetheless!!! ;)

http://www.lambdatechs.com/html/resources/247.pdf

http://www.lambdatechs.com/html/resources/245.pdf

Some of it may or may not be useful, but then again I may be wrong... It certainly wouldn't be the first time. :)

Respectfully,
Henry