Not enough information. What is the base metal thickness and is this an overlay or butt weld joint? Either way, you will need to butter the S275 base metal with 309L followed by deposition of the 316L with enough thickness to ensure a 316L chemical composition (if an overlay is specified versus a butt weld joint). If PWHT is decided, it should be done after the S275 has been buttered but before the 316L is deposited.
standard construction steel with sigma, yield = 275 MPa. european designation.
the first step up from S235 (sigma,yield = 235 MPa), that's the kind you can buy almost everywhere in hot and cold-rolled forms.
S275 belongs to carbon steel plate,it contains S275JR,S275J0 and S275J2 three different classes owning to the different low temperature when doing impacting test.