S32750 is a Super Duplex material (2507)and Avesta makes a filler metal, P100, that is designed specifically for welding the 2507. This steel has very high mechanical strength and very resistant to general corrosion, intergranular corrosion, pitting corrosion, but is origionally designed for it's great resistance to chloride stress corrosion cracking capabilities. Usiing a 316L filler metal will reduce the strength, chloride stress corrosion capabilities, and will lower the ferrite percentage in the weld metal. I will gladly send you a couple of papers I wrote, one for NACE and the other for general information when welding 2507, if you will send me your e-mail address.
Chuck