What is the intended application? Sticking together and suitable foor service are widely different ranges. The materials you mention have vastly different mechanical properties that require consideration during design annd engineering of a product.

Pieces joined together that are dis-similar may lose some of the properties in the WM or HAZ.  Both are weldable alloys and your best bet would to perform testing using filler metals suggested by the manufacturer. If none are suggested for the bimetallic weld, try one with each of the filler metals suggested for each base metal.

This would probably be best answered by someone familar with the application and service conditions. If you are making some Yard art, you have a great deal of fllexability, if you are making surgical implants or aerospace equipment,  its an entirely different story and in need of some actual research and testing that is far beyond the scope of online forums.

Consulting an actual metallurgist would be a great place to start however there very well may be some here that are familar with this material.  (More the Nickel Cobalt than the PH Stainless). In addition, you failed to mention the condition in which the 15-5 ph is supplied which would propably be of interest to someone smarter than I that ccould give you some real help.

Old welders like me,,, i just start with RN-82 if anything seems odd :)

Hopefuully you will find some help and welcome to the forum.

I'd like too ask, What brings you here? How did you hear about this forum? I would imagine working with those materials, you would be looking in quite a few places.

Have a great day and good luck. I'm looking forward to some responses that help you out. Tell us more about the product though.

Gerald Austin