HASTELLOY® S alloy is a nickel-base, high-temperature alloy with a unique combination of properties. It has excellent thermal stability, low thermal expansion and excellent oxidation resistance to 2000°F (1093°C). In addition, the alloy has good high-temperature and thermal fatigue strength. S alloy retains its strength and ductility after aging at temperatures of 800 to 1600F (427 to 871°C).

S alloy was developed for applications involving severely cyclical heating conditions where components must be capable of retaining their strength, ductility and metallurgical integrity after long-time exposure. It is used extensively as seal rings in gas turbine engines where its low thermal expansion coefficient is also important.