High Temperature Corrosion Behavior of C-HRA-2 Alloy in Advanced Ultra-Supercritical (A-USC) Coal Ash/Flue Gas Environment at 700 ℃

Scanning electron microscope, energy dispersive spectrometer and X-ray diffractometer were used to analyze the micro morphology, phase composition and element distribution of oxide film on the surface of C-HRA-2 alloy after corrosion in simulated advanced ultra-supercritical (A-USC) boiler coal ash/flue gas environment at 700 ℃ for 48 h and 120 h. And the high temperature corrosion behavior of C-HRA-2 alloy was analyzed. The results showed that the oxide film on the surface of C-HRA-2 alloy was mainly composed of an outer oxide layer, a middle mixed layer and an inner layer of sulfide. The outermost oxide layer was mainly eutectic sulfate with low melting point, there were NiO layers of different sizes below it. The middle layer was mainly composed of chromium oxides, sulfates and Mo₂S₃. The inner layer of sulfide was mainly discontinuous Mo₂S₃, which penetrated deeply into the alloy matrix. The ash reacted with molybdenum element in C-HRA-2 alloy to form molybdate on the surface of the alloy. With the prolongation of corrosion time, the nickel was continuously oxidized, the NiO layer thickened, the sulfur element was continuously diffused inward, and the thickness of Mo₂S₃ sulfide layer was increased, the corrosion continued to intensify.