INCOLOY® alloy 909 (UNS N19909) is a nickel-iron-cobalt alloy whose outstanding characteristics are a constant low coefficient of thermal expansion, a constant modulus of elasticity, and high strength. The alloy is strengthened by a precipitation-hardening heat treatment made possible by additions of niobium and titanium.

The combination of low expansion and high strength makes INCOLOY alloy 909 especially useful for gas turbines. The low expansion enables closer control of clearances and tolerances for greater power output and fuel efficiency. The high strength increases strength-to-weight ratios for lower weight in aircraft engines. For those reasons, INCOLOY alloy 909 is used for gas-turbine vanes, casings, shafts, and shrouds.

The properties of INCOLOY alloy 909 are attractive also for rocket-engine thrust chambers, ordnance hardware, springs, steam-turbine bolts, gauge blocks, instrumentation, and glass-sealing applications.