Si对AlCoCrFeNi高熵合金热腐蚀行为的影响研究

Effect of Si Addition on Hot Corrosion Behavior of AlCoCrFeNi High Entropy Alloys

摘要:

采用真空电弧熔炼法制备了AlCoCrFeNiSix（x=0, 0.2, 0.5, 0.8, 1.0）高熵合金，利用75% Na2SO4 + 25% NaCl（质量分数）热盐涂覆的方法，对比研究了Si的添加及其含量对等摩尔比AlCoCrFeNi高熵合金在950℃下热腐蚀行为的影响。结果表明：经100h热腐蚀后，由于发生Al的选择性氧化，合金表层相组成由BCC转变为FCC。适量Si的添加，会促使合金表面快速生成单一Al2O3膜，提高合金的热腐蚀抗力。但随着Si含量的增加，合金表面生成了由Al2O3和富Cr-Fe-Co-Si的尖晶石氧化物组成的混合氧化产物，且在氧化膜生长应力和腐蚀性介质（氧化-硫化-氯化）的协同作用下，组织疏松易脱落，合金发生严重的内氧化和内硫化。

Abstract:

AlCoCrFeNiSix (x=0, 0.2, 0.5, 0.8, 1.0) high entropy alloys were prepared by vacuum arc melting. The effects of Si addition and its content on the hot corrosion behavior of AlCoCrFeNi alloys at 950℃ in mixed salt of 75% Na2SO4 + 25% NaCl (mass fraction) were investigated. The results showed that the surface phase composition of the alloys changed from BCC to FCC due to selective oxidation of Al after 100h hot corrosion. A single Al2O3 scale could be formed preferentially on the surface of the alloy by adding proper amount of Si, and the hot corrosion resistance of the alloy can be improved significantly. However, the mixed oxides scales mainly composed of Al2O3 and Cr-Fe-Co-Si enriched spinel oxides formed on the surfaces of the alloys with the increase of Si content. Under the synergistic action of the growth stress of mixed oxides scale and the multi-element corrosion medium (oxidization-vulcanization-chlorination), the oxide scales were loose and easy to fall off, and serious internal oxidation and vulcanization were observed in the alloys.