Hi

You can easily weld the SDSS to C/S with the normal SDSS filler. If you need to perform PWHT to the C/S due to code requirements, then it would be best to butter the C/S side of the joint with the Inconel filler, perform PWHT and then weld the SDSS to C/S using an Inconel filler.

You can certainly also perform the weld with a 309 filler, but not sure why you would want to do that.

The question as to whether PWHT is required, needs to be answered by the code. At 40mm thick, for C/S, it would often be the case, but needs to be confirmed by looking at the relevant code. In terms of pre-heats and interpass temperatures, you would normally want to stick to temperatures that are between those that are most conservative. Normally for the SDSS, pre-heats and interpass temperatures need to be low, while for the thick C/S, they need to be higher. If possible select temperatures that are allowed by both. (e.g. Pre-heat for C/S:70°C (say) and max interpass for SDSS:150°C(say) - Then have a pre-heat of 70°C with max interpass of 150°C) If you are using a buttering of the C/S with a PWHT, then when welding against the SDSS, use the pre-heats and interpass temperatures you normally would use for SDSS.

Hope this helps.

Regards
Niekie

It would also depend upon the super duplex of which you speak. There is a concern with nitrogen bearing alloys being welded with Cb stabilized fillers, as is the case with NiCrMo-3. The combination precipitates columbium nitrides that have been shown in experiments to contribute to microfissuring. This issue gained most notoriety, with the utilization of NiCrMo-3 as the original workhorse filler for super austenitic and nitorgen containing AL6XN.