Microstructure and High-Temperature Chloride Salt Corrosion Behavior of New Ni–Cr–Mo Alloys

The influence of Mo content on the microstructure, mechanical properties, and high-temperature molten salt corrosion behavior of Ni–Cr–Mo alloys was systematically investigated. After solution treatment, grain refinement was observed with increasing Mo content. Mo-enriched precipitates were observed only in the alloy with 26 wt.% Mo. After exposure to molten NaCl-KCl salt at 700–900 °C, corrosion resistance improved with Mo content up to 24 wt.% but deteriorated at 26 wt.%. All alloys formed a protective oxide scale that consisted of Cr₂O₃, NiO, and NiCr₂O₄. However, its integrity progressively degraded with increasing temperature, transitioning from dense and adherent at 700 °C to porous and cracked at 900 °C. Ni₂(Cr,Mo) phase precipitation was induced during corrosion, and its volume fraction increased with both Mo content and temperature. These Mo-enriched precipitates and abundant Ni₂(Cr,Mo) precipitates may disrupt oxide scale continuity and may initiate localized galvanic corrosion. Ni–15Cr–24Mo showed the most balanced performance among the compositions investigated under the present test conditions. These findings provide important experimental data and theoretical reference for the design of corrosion-resistant alloys for high-temperature chloride environments.

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