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Incoloy. alloys 800H and 800HT. have significantly higher creep and rupture strength than Incoloy. 800. The three alloys have nearly identical chemical composition limits. However, the chemical composition limits vary with carbon, aluminum and titanium. The carbon content of Incoloy. alloy 800 (UNS n08800) is 0.10% max with no limit on the lower end. The carbon content for Incoloy. alloy 800H (UNS N08810) is 0.05% to 0.10% which is the upper end of the 0.10% maximum specified for Incoloy. alloy 800. The chemical limits for Incoloy. 800HT. (UNS08811) are even more restrictive yet still within the limits specified for Incoloy. 800H. The carbon content for Incoloy. alloy 800HT. is further restricted to 0.06%-0.10%. Additionally the Al plus Ti content of Incoloy. alloy 800HT. is restricted to 0.85%-1.20%. Note that the chemical composition for Incoloy. alloy 800HT. will always be within the limits of Incoloy. alloy 800H. Note also that the limits for Incoloy. alloy 800H may or may not be within the limits of Incoloy. alloy 800HT..
In addition to the controlled carbon content, Incoloy. alloys 800H and 800HT. receive a high temperature annealing treatment that produces an average grain size of ASTM 5 or coarser. The annealing treatment and restricted chemical composition are responsible for these alloys having greater creep and rupture strength.
The mechanical properties of Incoloy. alloys 800H and 800HT., combined with their resistance to high temperature corrosion, make these alloys exceptionally useful for many applications involving long-term exposure to elevated temperatures and corrosive atmospheres. In the hydrocarbon processing industry, these alloys are used in steam/hydrocarbon reforming for catalyst tubing convection tubing, pigtails, outlet manifolds, and quenching-system piping; in ethylene production for both convection and cracking tubes, and pigtails; in oxy-alcohol production for tubing in hydrogenation heaters; in hydrodealkylation units for heater tubing; and i the production of vinyl chloride monomer for cracking tubes, return bends and inlet and outlet flanges.
Industrial heating is another area of wide usage for both Incoloy. 800H and 800HT.. In various types of heat treating furnaces, these alloys are used for radiant tubes, muffles, retorts, and assorted furnace fixtures.
Alloys 800H and 800HT. are also used in power generation for steam superheating tubing and high temperature heat exchangers in gas cooled nuclear reactors.