Alloys 800H (UNS N08810) and 800HT (UNS N08811) are dualcertifiable Nickel-Iron-Chromium materials that resist oxidation, carburization, and other high-temperature corrosion. The chemical composition of the two alloys is identical to Alloy 800 (UNS N08800), with the exception of the higher level of carbon present in both grades —(0.05 – 0.10%) in alloy 800H, and(0.06 – 0.10%) in alloy 800HT. Alloy 800HT also has an addition of up to 1.0% aluminum and titanium. In addition to the chemistry restrictions, both alloys receive a high-temperature annealing treatment that produces an average grain size of ASTM 5 or coarser. The restricted chemical compositions, combined with the high temperature anneal, assure these materials have greater creep and rupture strength when compared to Alloy 800. Alloy 800H has good creep-rupture properties at temperatures.