Alloys 800(UNS N08800), 800H(UNS N08810),and 800HT (UNS N08811) are extensively used in industrial heating, power plants, and petrochemical industries due to their good corrosion resistance. Under certain high temperature service conditions M23C6-type carbides... Keywords: Alloys 800, 800H, 800HT, thermal stability, tensile testing stress rupture properties