Q: I’m running a high temperature ethylene process that will reach 750-850C. I need a fastener that is carburization and creep resistance. Also moderate corrosion can be an issue. Any suggestions on materials?

A: This process is ideal for Incoloy 800H or 800HT bolting. These materials are designed for long-term high temperature use. These specialty alloy fasteners are typically used in temperatures above 1500°F where creep and stress rupture protection required. Incoloy bolts also offer moderate corrosion resistance to seawater, brine, sour gas, chlorides and sulfur containing atmospheres as well as oxidation and carburization. However depending on the size you need Incoloy fasteners may have limited availability so Inconel 600 bolts would be a safe bet as well.

Molybdenum can be used to over 2900F but only in a vacuum where oxygen isn’t present, otherwise it will oxidize quickly. For the temperatures you are dealing with in an air-rich environment, I would suggest Inconel 600 which is usable to 2000F in air or a ceramic like alumina which is usable to 3000F.