Incoloy 907 and 909 (UNS N19907 / N19909) are precipitation-hardenable iron-nickel-cobalt alloys containing 35-40% nickel and 12-16% cobalt with a balance of iron, strengthened by niobium and titanium and designed to combine high strength with a low, nearly constant coefficient of thermal expansion. The cobalt addition raises the Curie temperature, extending the low-expansion range to considerably higher temperatures than Invar, and the alloys retain high strength up to approximately 650°C (1,200°F). Because they contain no chromium, their oxidation resistance at high temperature is limited. Alloy 909 adds silicon (0.25-0.50%) to improve notch-rupture strength over alloy 907. They are used where tight clearances must be held through temperature changes, including gas turbine casings, seals and shafts, rocket-engine thrust chambers and steam-turbine bolts. DASM supplies Incoloy 907 / 909 as vacuum-melt quality (VQ) feedstock: every piece is sorted and analyzed, cut to size and shot-blasted on all surfaces for direct furnace charging.

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