Corrosion of Stainless Steels In Supercritical Water

Abstract

The behavior of stainless steels, including both hardenable and nonhardenable grades, in degassed super-critical water at 800, 1000, and 1350 F and a pressure of 5000 psi is described. In general, the corrosion at 1350 F observed for the alloys was found to be intergranular, while at 1000 F, only Inconel X exhibited selective penetration along grain boundaries. All alloys suffered some decarburization and carbide precipitation after exposure to supercritical water at 1350 F. No significant phase changes were observed at 800 and 1000 F. The Armco 17-4PH, Armco 17-7PH, and Hastelloy F alloys were the most resistant materials at 1350 and 1000 F. All of the alloys evaluated had excellent resistance to 800 F degassed supercritical water. The AISI Type 316 material was shown to be susceptible to stress-corrosion cracking at 1350 F. 4.6.5