Nickel Incoloy 909

Nickel Incoloy 909 (UNS N19909) is a precipitation-hardenable nickel-iron-cobalt superalloy. It combines high strength with a low, nearly constant coefficient of thermal expansion of about 4.3 x 10^-6 in/in/°F (7.7 µm/m·°C) from room temperature to around 800°F (425°C). It keeps most of its room-temperature strength up to 1200°F (650°C). Its silicon addition, together with very low aluminum, gives better resistance to stress-accelerated grain-boundary oxygen embrittlement (SAGBO) and lower notch sensitivity than earlier low-expansion grades such as Incoloy 903 and 907.

The alloy is hot worked between 1600°F and 2050°F (870-1120°C), is readily welded by the gas-tungsten-arc process, and is best rough machined in the solution-annealed condition. It reaches full strength with a two-step aging treatment. Room-temperature tensile strength is about 185 ksi (1276 MPa), and it keeps about 150 ksi (1034 MPa) at 1200°F. Because it contains no chromium, it is ferromagnetic below its Curie temperature and resists hydrogen embrittlement.

Incoloy 909 is used wherever tight clearances must hold across a wide temperature range. Typical parts include gas turbine casings, shrouds, vanes, seals and shafts, rocket-engine thrust chambers, ordnance hardware, springs, steam-turbine bolts, gauge blocks, instrumentation and glass-to-metal seals.

Tech Steel & Materials offers the alloy Nickel Incoloy 909 in 3 sub-type specifications, each in multiple and customized shapes/forms:

• AMS 5884 (Bar, Forging, Ring or Custom Tube)
• AMS 5892 (Sheet, Strip)
• AMS 5893 (Bar, Forging, Ring or Custom Tube – short-time aging grade)

Incoloy 909 is supplied solution heat treated. Its strength comes from gamma-prime precipitation during aging. The standard treatment is a solution anneal at 1800°F (980°C) for 1 hour with an air cool. This is followed by aging at 1325°F (720°C) for 8 hours, furnace cooling at 100°F (55°C) per hour to 1150°F (620°C), holding for 8 hours, and air cooling. AMS 5893 material is made to respond to a shorter aging cycle. Parts brazed above 1800°F use the higher 1425°F first-step age.

Mechanical Properties Of Incoloy 909

Typical values for solution-annealed and aged material. For minimum guaranteed properties, refer to the applicable AMS specification.

Physical Properties Of Incoloy 909

Incoloy 909 is the third generation of Special Metals’ controlled-expansion superalloys. Incoloy 903 relied on aluminum for strength, which made it prone to SAGBO and notch sensitivity. Incoloy 907 cut aluminum below 0.2%. Incoloy 909 goes further, adding about 0.4% silicon, which improves notched stress-rupture strength and allows simpler heat treatment. Compared with Inconel 718, 909 expands roughly 40% less. It has no chromium, however, so it needs a protective coating for long exposure to oxidizing conditions above about 1200°F (650°C).