If you intended 308 as your filler in the question, or a varying alloy as the filler, the answer is, in my opinion, it depends upon the service intended. If, by specifying 316, they intend pitting resistance with the Mo, then you would be well served to stick with 316. However, if 316 is specified for strength purposes(since the Mo adds strength to the material), then 308 has been found acceptable, since the WM will demonstrate greater strength than annealed 316 BM and therefore match the 316 BM. Bottom line, there is no absolute rule to alloy mathcing for SS's. But when in doubt about the service, or the metallurgy of the allys, its best to match 316 with 316, and 308 with 304, etc.
Jeff, if I may elaborate just a little regarding moly in a 316 filler metal. The main purpose of moly in a SS is that moly supports chromium in providing chloride corrosion resistance. But, in the 316 in particular, when a SS contains at least 18% chromium, the additions of moly become about 3 times as effective as chromium additions agaainst pitting corrosion in chloride containing environments. And, as you said, it adds strength at elevated temperatures.
Thanks Chuck.
Your elaborations are always welcome.
Thanks, Jeff, as I most assuredly enjoy your responses. We have had some quite interesting discussion.
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