Surface chemistry and corrosion behavior of Inconel 625 and 718 in subcritical, supercritical, and ultrasupercritical water

Abstract

Corrosion behavior of Inconel 625 and 718 in subcritical, supercritical and ultrasupercritical water was studied as a function of temperature and time. The change in the chemistry of the as-received surface film on Inconel 625 and 718 after exposure to subcritical water at 325°C and supercritical water at 425°C and 527.5°C for 2 hours was studied. After exposure to 325°C subcritical water, the CrO4 2based film formed; however minor quantities of NiFexCr2-xO4 spinel compounds were observed. The oxide film formed on both alloys when exposed to supercritical water at 425°C consisted of NiFexCr2-xO4 spinel. The surface films on both alloys were identified as NiFe2O4 when exposed to supercritical water at 527.5°C. To characterize the fully developed oxide layer, studies were conducted at test solution temperatures of 527.5 and 600°C. Samples were exposed to these temperatures for 24, 96, and 200 hours. Surface chemistry was analyzed using Xray diffraction, as well as Raman and X-ray photoelectron spectroscopies. Inconel 718 exhibited greater mass gain than Inconel 625 for all temperatures and exposure times. The differences in corrosion behavior of the two alloys are attributed to the lower content of chromium and increased iron content of Inconel 718 as compared to Inconel 625.

Degradation of Incoloy‐800HT in molten FLiNaK salt at high temperatures

“…These spinel oxides have a characteristic Raman shift of approximately 660–710 cm −1 in Raman spectroscopy. [ 26–29 ] The change in the Raman shift with the exposure time (at both the temperature) indicates a change in the composition of this phase. …”

Imaging XPS for industrial applications

“…XPS imaging has therefore understandably found application in the areas of oxidation, corrosion and magnetism [26][27][28][29][30], surface binding and diffusion [31,32], polymer surface chemistry [27,[33][34][35] and geological applications [36]. What follows are examples of different applications where imaging XPS has been successfully applied to industrially relevant situations.…”

“…One of the greatest issues industry faces is the failure of manufactured parts, which is typically caused by oxidation or corrosion [28,42]. Imaging XPS has been successfully applied to many systems, including adhesive joint failure [43], pitting corrosion in Inconel [26], Ni-Cr-Mo alloys [44] and the analysis of contaminated channelplates [45].…”

Oxidation Behavior of Nickel Based Alloys in Supercritical Water Environment

“…The characteristics of nickel-based alloys are given by resistance to high temperatures and hardness. It has good creep resistance, high surface stability and excellent resistance to oxidation and corrosion at high temperatures [5][6][7][8]. Thus, nickel based alloys are in high content in Ni, Cr, which could increase the oxidation and corrosion resistance at high temperatures [9][10][11][12].…”