鉻鉬鋼於LiNO_3-NaNO_3-KNO_3共晶融鹽的熱腐蝕

Hot Corrosion of Cr-Mo Steel in Molten LiNO3-NaNO3-KNO3 Eutectic Salt

本研究採用不同鉻含量之鉻鉬鋼（0、2.25、5、9、12 wt% Cr），於550℃氮氣保護氣氛之LiNO3-NaNO3-KNO3共晶融鹽進行250、500與1000小時之靜滯腐蝕實驗，目的為探討鋼料鉻含量對於其於融鹽中的熱腐蝕行為影響。研究結果顯示，各鋼料的質量增重皆與腐蝕時間成正比，並且隨著鋼料鉻含量的增加，其質量增重大幅降低。鋼料腐蝕後的顯微結構分析顯示，各鋼料的腐蝕皮膜皆由外側LiFeO2與內側(Fe,Cr)3O4組成，其厚度隨鋼料的鉻含量增加而減薄。綜觀本研究之結果，鋼料抵抗融鹽腐蝕的能力，在鉻含量達到9 wt%時可以得到大幅改善。

This study investigated the effect of the chromium on the hot corrosion behavior of Cr-Mo steels in a mixed molten salt. The corrosion test was performed by immersing Cr-Mo steels with different chromium content (0, 2.25, 5, 9, 12 wt% Cr) in static molten LiNO3-NaNO3-KNO3 eutectic salt at 550 ℃ for 250, 500 and 1000 hours with nitrogen cover gas. The results show the weight gains of the steels are directly proportional to the duration of time while those are inversely proportional to the chromium content. The microstructure analyses of the corroded steels show the corrosion scales on the steels are composed of an outer LiFeO2 and an inner (Fe,Cr)3O4 layers. Also, the thickness of the scales decreased with increasing chromium content. According to the result of this study, it has been confirmed that the corrosion resistance of steels in the molten slat can be dramatically improved when the chromium content reached 9 wt%.