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.

Q: My customer is having an issue with his stainless steel fastener bending. They are being used in a high-heat application running at approximately 1600F. Is this normal? Any ideas?

A: This is definitely expected at these temperatures. If temperature and strength are you main focus, I would suggest either Inconel 600 screws or Alloy 330. Inconel is known for it’s high temperature strength offering a yield strength of 84ksi and a usable temperature limit of about 1800F. Inconel’s could used in air or in a vacuum.  Alloy 330 is another alternative as it has very similar high temperature properties but would be best suited inside a vacuum to minimize oxidation.

Q: I have a high temperature application which is exposed to sulfur and chloride gasses. We’re operating at between 1200° and 1400°F. Any suggestions on a bolt material to consider?

A: To deal with both sulfuric/chloride atmospheres as well as high temperatures, you may want to consider Incoloy 800HT bolts or an Inconel 600 bolts depending on the concentrations of the acid gasses. Incoloy is an ideal material for long-term exposure in high temperature environments due to its oxidation, carburization and creep resistance. Incoloy 800 series bolts are all similar and considering your temperature range, I would suggest the Incoloy 800HT since it will not become embrittled even after long periods of usage in the 1200-1600° F. However if you have more severe corrosion issues especially during shut downs or equipment cycling due to acid gasses or condensation formed by the sulfur and chlorine components combining with water, the Inconel fasteners will provide better corrosion resistance than Incoloy.