May I offer something? I realize this is an older discussion. Look up the material specification for the metal type you are working with. SSTL 904L is a molybdenum alloyed stainless designed for general fabrication with good resistance to chlorides. The machining, forming, and welding characteristics, plus the hardness, tensile strength etc will be given on the specification. For example: https://www.sandmeyersteel.com/904l.html
On a slightly different subject, here's something I learned about Rolex servicing and parts.
I engraved a Tudor bronze that I purchased used. The bezel had a couple of chips in it so I contacted my Rolex watchmaker friend who works for an authorized Rolex dealer. He told me the bronze Tudor is a "restricted model" and he can't get certain parts for it so it has to go back to Rolex. And since it's engraved, Rolex won't touch it because I've committed a grave sacrilege with unauthorized modifying one of their watches. So I was screwed with getting a replacement bezel insert.
Rolex has also shut down supplying parts to Rolex certified watchmakers that don't actually work in a dealer's store. This is a real game changer if parts are needed and you've got an engraved restricted model that can only be sent back to Rolex for parts replacement like bezels, crystals, bracelets, etc. A private watchmaker can service it, but if parts need to be replaced it really complicates things.
It is true, Rolex watches sent to replace any parts should pass full service and be returned in like-new condition, and any engraved parts are considered "damaged" which might affect waterproofness, so require to be changed.
If the sertified watchmaker is a nice enough person he can still accept such watches on his own risk))