C-HRA-2合金在700 ℃先进超超临界(A-USC)锅炉煤灰/烟气环境中的高温腐蚀行为

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

采用扫描电镜、能谱仪和X射线衍射仪,分析了C-HRA-2合金在700℃的模拟先进超超临界(A-USC)锅炉煤灰/烟气环境中腐蚀48 h和120 h后表面氧化膜的微观形貌、物相组成和元素分布,并分析了C-HRA-2合金的高温腐蚀行为。结果表明:C-HRA-2合金表面氧化膜主要由外层氧化层、中间混合层和内层硫化物组成;最外层氧化层主要为低熔点的共晶硫酸盐,其下方存在尺寸不一的堎块状NiO层;中间层主要由铬的氧化物、硫酸盐和Mo_(2)S_(3)组成;内层硫化物主要为不连续分布的Mo_(2)S_(3),深入合金基体内部;煤灰与C-HRA-2合金中的钼元素反应,在合金表面生成钼酸盐,随着腐蚀时间的延长,镍不断被氧化,NiO层增厚,硫元素不断向内扩散,Mo_(2)S_(3)硫化物层厚度增加,腐蚀不断加剧。

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 Mo_(2)S_(3). The inner layer of sulfide was mainly discontinuous Mo_(2)S_(3), 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 Mo_(2)S_(3) sulfide layer was increased, the corrosion continued to intensify.