Beyond Incoloy 800H: Why Inconel 602 CA is the New Standard for Ethylene Cracking Furnace Muffles

Incoloy 800H (UNS N08810) has been the traditional wrought muffle alloy, but above ~1050 degC its chromia-scale strategy breaks down and its creep-rupture design allowables effectively disappear. Inconel 602 CA (UNS N06025 / W.Nr. 2.4633) replaces the chromia-only defense with a yttrium-stabilized Al2O3 + Cr2O3 duplex scale and publishes validated creep-rupture data to 1200 degC. This article quantifies the difference with comparative oxidation, creep and carburization data tables and closes with a cost-to-service-life analysis showing why 602 CA is now the specification of record for 1100-1200 degC ethylene cracking furnace muffle duty.