空氣／氮氣氣氛對含沈積氯化鈉之鐵–（鉻）合金在850℃熱腐蝕之影響

The Effects of the Air / N2 Atmospheres on the Hot Corrosion Behavior of Fe-(Cr) alloys with NaCl Deposit at 850℃

本研究選用SB450、A24（2.25Cr-1Mo）、A26（9Cr-1Mo）、430SS等四種鐵（鉻）合金，表面沈積2 mg/cm2氯化鈉後置於850℃氣體流率為600 mL/min之空氣/氮氣氣氛中，探討環境氣氛對氯化鈉熱腐蝕之影響。實驗結果顯示，於空氣氣氛中，SB450呈現最大的金屬損失量，合金之金屬損失量隨著鉻含量之增加而減少。SB450與A24生成由外至內依序為Fe2O3、Fe3O4、Fe1-XO的三相氧化層結構；A26與430SS合金則生成外層氧化鐵、內層為氧化鉻的皮膜形態。於氮氣氣氛中，氯氧化反應因缺氧而無法發生，四種合金均只有輕微之金屬損失量；其中，A26與430SS合金之氧化層，以低氧平衡解離壓的氧化鉻為主。

The purpose of this study is to investigate the effects of alternative air/N2 atmospheres on the hot corrosion behavior of four commercial steels (SB450, STP A24, STP A26 and 430SS) with NaCl deposit. Corrosion tests were carried out at 850℃ with a const flow-rate of 600 mL/min. In the air atmosphere, the results showed that the metal loss decreased with increasing chromium content and the SB450 had the greatest metal loss among the four alloys studied. The scales formed on A24 and SB450 were triple layer of Fe2O3, Fe3O4, and Fe1-XO from the outer to the inner. The high-Cr-content alloys (A26 and 430SS) formed an outer layer of iron oxide and an inner layer of chromina. In the N2 atmosphere, oxychlorination did not occur, and all specimens only had slight metal loss. Only chromina formed on the high chromium content alloys (A26 and 430SS) due to its low dissociation pressure of oxygen.