Changing the Structure of a Single-Crystal Ni-Based Superalloy During Its High-Temperature Salt Corrosion at 750°C

The VZhM4 single-crystal Ni-based superalloy was tested for high-temperature salt-induced corrosion resistance in Na₂SO₄ + NaCl at 750°C. The equilibrium composition of phases formed during the interaction of the alloy with oxygen and sulfur across the temperature range of 600 – 1000°C were calculated. Changes in the structure and composition of the surface layer of the alloy during high-temperature salt corrosion were studied using scanning and transmission electron microscopy. The results obtained were used to compile structural diagrams for the corrosion layer formed on the alloy after 5 and 20 test cycles. The quantitative composition of the main phases in the corrosion products was determined. A qualitative assessment of Re, Ta, and Ru diffusion was performed.