Corrosion resistance and microstructural stability of austenitic Fe–Cr–Al–Ni model alloys exposed to oxygen-containing molten lead

Abstract

The goal of the study was to determine the critical concentrations of Al, Cr and Ni, at which the quaternary Fe-Cr-Al-Ni model alloys, exposed to oxygen-containing molten Pb up to 600°C, are corrosion resistant, while preserving the austenite structure of the alloy matrix. Twelve alloys were designed to meet the above mentioned requirements; six of them showed corrosion resistance and preserved the austenite phase in the alloy bulk, during the exposure at 550°C and 600°C for 1000 hours to molten Pb containing 10-6 wt.% oxygen. Based on experimental results a general formula was substantiated as follows: Fe-(20-29)Ni-(15.2-16.5)Cr-(2.3-4.3)Al (wt.%). In case of temperatures below 550°C, the critical Cr content was 14.4 wt.%. Two corundum-type crystalline structures were identified as the constituent phases of the passivating scales, one being Cr2O3 and the other Al2O3-Cr2O3 solid solution. The average amount of Cr2O3 in the Al2O3-Cr2O3 solid solution, found in the passivating scales of the Fe-Cr-Al-Ni model alloys, was estimated at ≈ 40 wt.% at 550°C and ≈ 35 wt.% at 600°C. A transitional layer, consisting of Fe-and Ni-enriched austenitic matrix and exhibiting randomly distributed intermetallic B2-(Ni,Fe)Al, was formed below the oxide scale up to a depth of two microns. The austenite, as matrix, and Ni3(Al,Fe) as precipitates are the microstructural phases of the bulk alloys after exposure for 1000h at 600°C to oxygen-containing molten Pb.

Experimental Investigation on the Cleaning Effect and Influence Rule of Hydrogen Peroxide–Acetic Acid on Lead–Bismuth Eutectic Alloy

“…The most commonly applied cleaning lotion of lead-bismuth alloy consists of three components, including an oxidant (hydrogen peroxide, H 2 O 2 , 30% aqueous solution), an acid (concentrated acetic acid, CH 3 COOH, > 96% aqueous solution), and a solvent (ultrapure water or ethanol), typically with a volume ratio of 1:1:1, and the cleaning process should be performed normally at room temperature. This cleaning method defined by Schroer ( 2015) is adopted as a standard procedure by many research groups in their routine laboratory applications (Fazio et al, 2003;Ejenstam et al, 2013;Shi et al, 2019;Gong et al, 2021).…”

A Review of the Surface Modifications for Corrosion Mitigation of Steels in Lead and LBE

“…In contrast, 14Ni AFA did not suffer from dissolution attack tanks to the formation of a thin protective (<100 nm) Al rich oxide after one year of exposure in liquid lead at 550 • C. However, the austenitic structure transformed into ferrite. In view of maintaining the austenitic structure, the research of Shi et al [81] aimed at determining the concentration ranges of the alloying elements (Cr, Al, and Ni), for which quaternary FeCrAlNi-based model alloys exhibit corrosion resistance in liquid lead at 600 and 550 • C (oxygen contain equal to 10 −6 wt.%), while preserving the austenitic structure as the alloy matrix. In case of application temperatures less than 550 • C, the critical Cr content was found at 14.4 wt.%.…”

Alumina-Forming Austenitic (AFA) steels and aluminium-based coating on 15-15 Ti steel to limit mechanical damage in presence of liquid lead-bismuth eutectic and liquid lead

“…Among the solutions explored over the past 10 years [6], one of the most promising seems to be the presence of a layer of alumina on the surface of steels, because of its stability whatever the oxygen content in the liquid metal [1]. Two types of solution have been proposed: 1. the development of Al2O3 coating to protect the steel [7][8][9], 2. the development of adapted steels containing aluminum to promote the insitu formation of a stable and protective Al2O3 oxide layer [3,[10][11][12][13][14][15][16]. Note that concerning the coatings, one of the problems could be the damage of the steel in the case of surface deterioration of the coating (cracking, wear, scaling, delamination, dissolution).…”