For Led Myne's 15th birthday, I replaced her 316 ss chainplates with:
* 2205 duplex ss (for most chainplates); and
* 2507 super duplex ss (for chainplates that were at the waterline or subject to significant spray and dunking).
These were external chainplates.
Three pairs of shroud
c'plates had to be curved to fit the shape of the hull
and with one or two slight bends. A couple of other c'plates had to have an slight bend. Three or more c'plates needed lugs welded onto them.
For what little it is worth, I sourced the plate 2205 and 2507, laser cut to shape, from Sterlings at Coopers Plains. I carried the plate to NRG Piping at Beenleigh for pressing (curving and bending), welding, and polishing (to mirror No. 8). Those enterprises just happen to be reasonably local to me (although far enough to pack a cut lunch for the journey).
NRG Piping had massive experience working with duplex ss and super duplex ss. I discussed with them the particular characteristics of welding duplex. They were more than familiar with what I had learned from my research
No annealling, just controlled speed and lubricated drilling to avoid overheat.
Led Myne's external c'plates are attached with carriage bolts. Enamoured by the idea that fasteners ought be a grade more resistant to oxygen-starvation corrosion and chlorine ion-induced corrosion than the c'plates, I went to Anzor Fasteners at Acacia Ridge (also fairly local if you accept the need to pack a cut lunch for the journey) and asked them to source carriage bolts and nuts in 2507 super duplex ss. I suspect Anzor sourced them from somewhere in NW Eurasia but since I left that to them I really have 0 knowledge of the source.
As mentioned above, Sterlings supplied the duplex and super duplex plate laser cut to size. Sterlings also laser cut the square holes to accommodate the square necks of the carriage bolts. I figured that meant less stress (Led Myne's original 316 ss c'plates showed stress corrosion cracks originating at the corners of a couple three of those square holes. The fabricator of the original c'plates had I guess drilled the 316 plate and then filed the circular holes to make square holes).
I've discussed other detail of that project on CF in the past.