第四代核反應器之一的超高溫氣冷式反應器(VHTR) ， 其設計以氮氧作為工作流體，爐心出口溫度達 700 0C 至9500C '且為了達到更高的發電效率(> 50%) ， 最終目標為1000 0C 以上的操作溫度。在這樣的高溫 環境下，冷卻劑中的微量雜質， 或發生進氣事故中流人的氣體，都可能加速結構材料的腐蝕速率。被開發 應用於飛機渦輪引擎元件的鎳基超合金，便因其在700 0C 以上高溫的熱阻抗性與抗腐蝕性，成為新型核電 廠中間熱交換管(1取)的候選結構材料。本研究還用以氧他錯作為其防護層的Inconel625 與Hastelloy C4' 以及以氧他鋁作為保護層的HR-224 三種鎳基超合金作為待測材料， 探討其在850 與950 0C 的氮氧環境 下，不同濃度之氧氣水氣雜質所造成的氧他行為影響。而氧f 七測試的結果顯示，溫度的提高使三種合金的 氧他速率均上升， Inconel 625 在950 0C 下表現出三合金中最大的單位質量變他。而在所有測試條件下 Inconel 625 、Hastelloy C4 都在表面形成連續的氧他錯層，其下則可見氧他鋁內氧忱的出現。但僅有 Hastelloy C4 ' 在特定氧f七條件中被發現有孔洞出現於氧他層與基材界面處。而以形成氧他鋁作為保護層 的HR-224 合金，則隨著氧f七條件的差異在表面出現氧他錯、氧f 七矽等其他氧f 七物，氧他層剝落的情形也 在水氣條件中更為嚴重。本研究亦會利用分析所得結果與相關文獻討論三種合金的氧他機制。

The Very-high-temperature Reactor (VHTR) is one of the Gen-IV reactors. Helium is usedps the coolant of a VHTR and the core outlet temperature can achieve 700-950oC, which might reach up to 1000oC for higher efficiency in the future. At such high temperature, the impurities from original coolant or a loss-of-coolant accident (LOCA) may have a significant impact on the performance of structural materials. As the promising candidate materials for Intermediate Heat Exchanger (IHX), chromia formers Inconel 625 and Hastelloy C4 alloys and alumina former HR-224 alloy should be tested in further studies to prove their corrosion resistant ability. In this research, three alloys were tested at 850〇C and 950〇C in helium environments with various concentrations of 〇2 and H2O. In general, the oxidation rates of all the alloys increased with the increasing temperature, and Inconel 625 alloy showed the highest mass gain among the alloys at 950^. Continuous chromium oxide layer with internal alumina was formed on the surface of Inconel 625 and Hastelloy C4 alloys in all conditions, while the alumina scale spalled and other oxides could be found on the surface of HR-224 alloy under specific conditions. Further analyses and oxidation mechanisms of these alloys would be presented in this study.