Study on the Hot Corrosion Behavior of Nitrogen-Containing Nickel-Based Cladding Layer in Na2SO4 + NaCl Mixed Salt at 700°C

Abstract

Based on the core idea of replacing Ni with N, this article designs a nitrogen-containing nickel-based alloy powder for plasma cladding. The corrosion behavior of Inconel 625 and the nitrogen-containing nickel-based cladding layer in a mixture of 75% Na₂SO₄ + 25% NaCl at 700°C was studied, and its mechanism was analyzed. The results of corrosion weight loss show that the corrosion weight loss per unit area of Inconel 625 is 2.95 times that of the nitrogen-containing nickel-based alloy. The results of XRD, SEM of surface corrosion and elemental distribution indicate that the phase compositions of Inconel 625 and the nitrogen-containing nickel-based alloy after corrosion are basically the same, all containing Cr₂O₃, NiO, Fe₂O₃, NiCr₂O₄, and Ni₃S₂. NiFe₂O₄ was also detected in the nitrogen-containing nickel-based cladding layer. Through the cross-sectional morphology and elemental distribution after the corrosion of the cladding layer, it can be seen that a chromium-depleted layer appears in Inconel 625 after corrosion, while it was not observed in the nitrogen-containing nickel-based cladding layer. In summary, the corrosion resistance of the nitrogen-containing nickel-based cladding layer to the Na₂SO₄ + NaCl molten salt is better than that of Inconel 625. It can be proved through the corrosion mechanism and XPS that Cr₂O₃ plays a crucial role in it.