Temperature Ranges

Nov. 15, 2002
Superalloys and exotic metals are used to make fasteners that withstand high temperatures.

Superalloys and exotic metals are used to make fasteners that withstand high temperatures. Austenitic alloys are the primary types for use at elevated temperatures. They includenonheat-treated alloys such as the SAE 30300 series of stainless steels, as well as Hastelloy, Inconel, and Monel, and precipitation-hardening alloys, such as AMS 5725, and 17-7PH.

Hot-heading techniques have produced fasteners that have physical properties satisfactory for use at 1,500°F.

Mechanical fasteners made from refractory metal are used for short-term (usually only a few hours) exposure to temperatures up to 3,000°F. Columbium fasteners are usable in the 2,000 to 2,600°F range and tantalum is preferred for the 2,800 to 3,600°F bracket. Tungsten is the only fastener material that survives above 3,600°F, despite its susceptibility to severe oxidation if uncoated. Over a period of time, existing coatings can deteriorate, which can lead to catastrophic oxidation of refractory metals at these temperatures. At cryogenic temperatures, threaded fasteners made from nickel and iron-based alloys have excellent mechanical properties.

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