I'm a little leary to post this, as most posts seem to be dominated by metal oriented people.
But have you considered epoxy vinyl ester/fiberglass? Most are good to 100C. If you want hotter than that, dual laminates are the method of construction of choice. Either a polyolefin or flouropolymer can be mechanically bonded to a fiberglass structure. Lastly, this type of construction can be stamped according to ASME Section X or RTP-1.
Fiberglass should be competitive in price to 316SS. I'm not familiar with the other alloy you mentioned. Dual laminates vary in price greatly depending on the type of flouropolymer used. A 12,000 gallon FEP-Teflon lined vessel is generally 20% lower in cost than Titanium Grade 7. This of course depends on size and the wildly fluctuating price of Titanium.
This is probably more than you ever wanted to know, but please let me know if you want more information.
Ghopkins
We metals types welcome the knowledge of you guys who know the non-metallic materials better than we do. I think we're all here to help each other and none of us should be parochial. As anyone who has tried to compare the relative merits of different materials and been frustrated by the lack of comparable data knows, it's not easy to really know all the real options.
There is an incredible amount of money wasted on more expensive materials than are needed for the job, as well as money wasted on materials that don't last. ( Anyone out there ever looked at the crummy highways and bridges in Pennsylvania?)
Let's continue to give the best help we can to out colleagues.
