Oxidation Behavior of Nickel Based Alloys in Supercritical Water Environment

Florentina Galan,Marian Catalin Ducu,Denis Aurelian Negrea,Manuela Fulger

doi:10.37358/rc.20.9.8328

Abstract

Corrosion resistance is a key performance factor for engineering materials used in the supercritical water-cooled reactors (SCWR). Choosing the materials with the best characteristics in the corrosive environment for SCWR, at high temperatures and pressures, is a real challenge for many researchers. Therefore, this paper aims to test two nickel-based alloys (Incoloy 800HT and Inconel 718) and to analyze the microstructures of the samples following exposure in a supercritical environment. Oxidation tests were performed at high temperature and pressure (550oC, 25MPa) for up to 70 days. The samples were investigated using gravimetric corrosion test and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX). The results obtained can be used in future research of the test protocol to identify alloys that could be used for SCWR components.

Highlights

The importance of developing new generations of nuclear power systems has led to the expansion of concepts for supercritical water-cooled reactors (SCWR), these reactors will operate above the critical thermodynamic point of water (Tc = 647.096 K, ρc = 0.322 g·cm-3 and Pc= 22.064 MPa)
The SEM results on Incoloy 800HT after oxidation for 70 days in Supercritical water (SCW) shown two types of areas with different colors developed on the surface
The energy-dispersive X-ray spectroscopy (EDX) analysis results indicated high percentages of iron and oxygen which suggest the presence of magnetite (Fe3O4)

Summary

Introduction

Nickel-based alloys are considered possible candidate materials for coating fuel tank and other components in the proposed supercritical water reactor, as they have been widely used in the design of nuclear power plants [1-4]. The characteristics of nickel-based alloys are given by resistance to high temperatures and hardness. The nickel-based alloys Incoloy 800HT and Inconel 718 were chosen, because they have the optimal balance of structural strength and corrosion resistance required for applications at high temperatures. The samples were exposed to supercritical water to study their behavior in the corrosive environment. These were investigated by gravimetry and scanning electron microscopy coupled with energy dispersive Xray spectroscopy

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