The environment that the MP35N will be seeing is High Temp, High Abrasive, CO2 and H2S. I am using this material for a stem. It is 1" dia round bar. I am looking to find a replacement for this material because it is so hard to get. I hav had delivery times as long as 32 weeks for raw material.
I don't think you will be able to easily replace this, meaning directly substitute one metal alloy for MP35N while retaining the same geometry, manufacturing process, etc. Abrasive wear means that titanium is not a great option, unless coatings can be considered, which then means a great many things need to be evaluated. If you are open to design and manufacturing changes then I am sure that there are other options available with shorter lead time.
Elgiloy is the other cobalt based alloy used for springs in sour service valves. A little crazy to use Cobalt alloy for a 1" stem when a Ni base alloy like 718 will usually be adeqaute.
Based on my slow strain rate testing experience I would not use 718. I would stick with a "C" alloy (C-22, 59, 686) or 625.
And no, 32 weeks isn't bad. I am waiting 18 weeks for high alloy cold rolled sheet, and that is an improvement from last year. Of course todays prices are through the roof, maybe that is why demand is down a bit......
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Rust never sleeps
Neither should your protection
Mmm, unobtainium! Not much out there commonly available with yield>200 ksi and very corrosion resistant.
By all means, ask SPS and Carpenter for advice, but as advised above, don't expect lead times of anything like this to be days rather than months.
Carpenter claim their Custom Age 625 PLUS Alloy can be cold worked and aged up to the sort of properties you're after. Its toughness may still be acceptable.
Also, MP159 may well be more readily available than MP35N, but probably not by much.
