Hot corrosion of Fe-Cr-Ni multi-principal element alloys in Na₂SO₄+25% NaCl mixture salts at 700-900C

This study investigates the hot corrosion of two multi-principal element alloys (MPEAs) and two commercial alloys when exposed to Na2SO4+25%NaCl at high temperatures ranging from 700 to 900 degrees C in ambient air. Above 800 degrees C, FeCrNi and FeCrNiCoMn exhibit superior corrosion resistance compared to 310S and Inconel 625. High concentrations of Fe and Ni in commercial alloys prove detrimental to hot corrosion resistance due to the formation of non-protective layers and induced alloy decomposition. Moreover, the exploration of critical partial pressure associated with oxidation, chlorination, and sulfurization activities aligns with the sequence of Mn > Cr > Fe > Co > Ni. The addition of Mn does not enhance hot corrosion resistance, as evidenced by poor adherence and high corrosion activity (i.e., lowest critical partial pressure of O-2) for Mn2O3. This comprehensive analysis concludes that element selection plays a pivotal role in optimizing hot corrosion resistance in MPEAs within the Fe-Cr-Ni system. Specifically, it advocates caution in using Mn and emphasizes the need to curtail Fe and Ni contents for strategic enhancement of hot corrosion resistance in such alloy systems.