Comparison of Hot Corrosion Behavior of Ni36Fe34Al17Cr10Mo1Ti2 and Ni34Co25Fe12Al15Cr12W2 Alloys in NaCl–KCl–Na2SO4 Salt

Abstract

Hot corrosion in molten salt is a complex process, involving both chemical corrosion and electrochemical corrosion. Interfacial reactions and oxide dissolution can also impact the corrosion results. Compared with single component/type salt, multi-component/type hot corrosion leads to more severe degradation, while the multi-component alloys offer potential chances for developing anti-corrosion metallic materials. In this study, we aim to elucidate the hot corrosion behavior and gain a better understanding of the corrosion mechanism of the multi-component alloys under multi-component/type NaCl-KCl-Na₂SO₄ salt. The corrosion behavior of dual-phase Ni₃₆Fe₃₄Al₁₇Cr₁₀Mo₁Ti₂ (HEA-1) and Ni₃₄Co₂₅Fe₁₂Al₁₅Cr₁₂W₂ (HEA-2) alloys was studied within NaCl-KCl-Na₂SO₄ molten salt with mass ratios of 5:5:1 and 5:5:2. After exposure to the salt at 650 °C for 168 h, it was found that the Ni₃₄Co₂₅Fe₁₂Al₁₅Cr₁₂W₂ exhibited better corrosion resistance than Ni₃₆Fe₃₄Al₁₇Cr₁₀Mo₁Ti₂. The improved performance of Ni₃₀Co₂₅Fe₁₂Al₁₅Cr₁₂W₂ alloy was attributed to the Co element, which facilitated the formation of dense oxides scale and enhanced scale adhesion. Alkali chlorides with stronger penetration ability dominated the corrosion process and alkali sulfate further aggravated the corrosion. The primary corrosion mechanisms involved in this process were identified as “electrochemical mechanism” attacking the body-centered cubic structure in the alloys and “active oxidation” causing dissolution of the alloy elements.