High-temperature corrosion behaviour of IN617 and AISI 304H alloys in mixed salt environment at 750 °C for power plant applications

Abstract

This study examines the hot corrosion behavior of Alloy 617 and AISI 304H under mixed salt environments at 750 °C, relevant to their use in reheater, superheater, and steam header tubing in advanced ultra-supercritical boilers. A 100-h cyclic hot corrosion test was conducted using 3–5 mg/cm² salt mixtures (75% Na₂SO₄ + 25% NaCl and 75% Na₂SO₄ + 20% NaCl + 5% V₂O₅). Corrosion kinetics were monitored through weight gain measurements, while SEM/EDS and X-ray diffraction (XRD) analyzed surface and cross-section morphology. Results showed IN617 exhibited better resistance in the Salt 1 environment, whereas SS304H performed better in Salt 2, as indicated by lower weight gain and parabolic rate constants. Higher chlorine and vanadium content accelerated corrosion, promoting cracks and voids from molten chlorides. Oxide scales formed at high temperatures were enriched with Ni, Cr, Fe, and O, alongside other reactive species.