Q: I need a 12 point bolt for a vacuum application with low off-gassing, min yield of 120 ksi, low magnetic permeability and minimum operating temps of 400C / 750F. Is Inconel 718 a good choice?
A: An Inconel 718 bolt will certainly work. The only other material you may want to consider would be an A286 in the cold worked version which will get you a min Tensile of 160ksi and a min yield of 120ksi. A286 bolts are readily available in a Socket Head Cap Screw design (if lead time is important) but if you need a 12 Point it could be made that way. Same is true for Inconel 718.
For more information on A286 see the link: https://www.extreme-bolt.com/