INCOLOY® alloy 909 (UNS N19909) is a nickel-ironcobalt 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 chemical composition of INCOLOY alloy 909 is given in Table 1. 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. Table 1 - Limiting Chemical Composition, % Nickel ..........................................................................35.0-40.0 Cobalt..........................................................................12.0-16.0 Niobium...........................................................................4.3-5.2 Titanium...........................................................................1.3-1.8 Iron ...............................................................................Balance* Silicon..........................................................................0.25-0.50 Aluminum....................................................................0.15 max. Carbon........................................................................0.06 max. In the continuing evolution of SMC-developed low coefficient of expansion superalloys, Special Metals Corporation has introduced INCONEL® alloy 783, offering these improvements over INCOLOY alloy 909: - Excellent resistance to oxidation to 1300°F (704°C) - Resistance to SAGBO comparable to that of  INCONEL alloy 718 - 5% lower density than alloys 909 and 718 -Better impact resistance -Processing characteristics comparable to alloy 718  *Reference to the ‘balance’ of a composition does not guarantee this is exclusively of the element mentioned but that it predominates and others are present only in minimal quantities.