Expansion Alloy Heat Treatment
Heat Treatment of Controlled Expansion Alloys Special Heat Treating Processing of Certain Nickel-Iron and Nickel-Iron-Cobalt Alloys Controlled low expansion, nickel-iron and nickel-cobalt-iron alloys are the alloys that are characterized by: an inflection temperature of at least 330 °C, a coefficient of expansion between ambient and inflection temperature not greater than 1 x 10 -6 per C., high room temperature tensile strength, improved elevated temperature stress-rupture properties, including notch-rupture strength, good notch ductility where notch bar rupture life exceeds smooth bar rupture life The controlled expansion alloys contain about 34% to 55% nickel , up to 25% cobalt, about 1% to 2% titanium, about 1.5% to 5.5% columbium, about 0.25% to 1% silicon, not more than about 0.2% aluminium, not more than about 0.1% carbon, with iron being essentially the balance. A more advantageous and preferred composition contains about 35% to 39% nickel, about 12% to 16% cobalt, about 1....