本研究主要是探討新開發之高熵合金的腐蝕行為及其電化學特性之研究，此系列合金非常特殊，高熵合金Co1.5CrFeNi1.5Ti0.5為FCC相，但其硬度比一般的FCC型合金高，為了進一步測試其實用性，因此做了一些材料腐蝕性質方面的研究；然而，Mo元素的添加有助於抗氯鹽之孔蝕，因此添加Mo元素於高熵合金內，改變Mo成份之莫耳比進行探討，並嘗試做加工和表面氧化的變化，並與商用304不□鋼做比較。
實驗分別於0.5 M硫酸與1 M氯化鈉溶液中進行，結果顯示：無論於室溫、高溫、高氯離子濃度環境下，Co1.5CrFeNi1.5Ti0.5Mox的抗孔蝕能力遠高於304不□鋼，當高熵合金還未到達孔蝕電位，304不□鋼的電流密度已經高於高熵合金104倍，而從循環極化以及SEM的結果，亦可明顯看出此高熵合金具有極佳的抗孔蝕能力。
於硫酸溶液中，此高熵合金極化曲線的結果顯示其抗蝕能力與304不□鋼相當，但是觀察腐蝕後的表面形貌，高熵合金腐蝕破壞的情形較為嚴重，可能為鑄造後形成之樹枝晶與樹枝間相所造成。添加Mo元素則可有效提升合金的抗蝕能力，但是隨者Mo含量增加至0.8份時，由於第二相的生成，反而使抗蝕能力下降；另外，將高熵合金浸泡於硫酸溶液中30天後，亦發現Co1.5CrFeNi1.5Ti0.5有明顯的樹枝晶結構，Co1.5CrFeNi1.5Ti0.5Mo0.1卻無明顯的樹枝晶結構。
測試均質化加工後之試片得知：對硫酸之抗蝕性有顯著的改善，因此可藉由其他方式之加工來改善其抗蝕性。表面氧化之試片，目的為觀察於表面生成一層薄的自生氧化物之後，是否有達到保護內部合金的效果，而本實驗利用於900 ℃下持溫4小時之製程參數生成的氧化物太厚；因為熱膨脹係數的差異，導致熱應力存在而容易剝落，應考慮縮短氧化時間，生成一層薄且附著力佳的氧化膜。

High entropy alloys (HEAs) are a newly developed family of multi-component alloys composed of at least five major elements, such as chromium, iron, nickel, aluminum, cobalt, titanium, copper, as well as molybdenum, etc. HEAs Co1.5CrFeNi1.5Ti0.5 has an FCC structure, a higher hardness than other FCC, good resistances to oxidation, and atmospheric corrosion. The potential applications of the HEAs are very significant. On the other hand, the addition of Mo, such as 304ss and 316ss, may have good pitting corrosion resistance.
To further understand the electrochemical properties of the HEAs, the HEAs Co1.5CrFeNi1.5Ti0.5Mox was conducted in 0.5 M H2SO4 and 0.1 M NaCl solution. The result of this study shows that the HEAs Co1.5CrFeNi1.5Ti0.5Mox have much higher pitting corrosion resistances (~1.2 V) than 304ss (~0.18 V) in the Cl- containing environments, as indicated by the significant differences in passive range as well as in pitting potential. The anodic polarization curves determined for Co1.5CrFeNi1.5Ti0.5Mox and for 304ss are very similar to each other in the chloride-free 0.5M H2SO4. However, the SEM images show that the surface morphology of the HEAs has been seriously damaged due to their cast-structure. The corrosion phenomenon will be discussed via electrochemical impedance spectroscopy together with the SEM observations.
The HEAs which was set in 1100 ℃ for 6 hours, then quenched by water is called homogenization. This kind of HEAs has good corrosion resistance in sulfuric acid solution. The oxidation film of HEAs was too thick. It was under the 900℃environment which was filled with oxygen for 4 hours treatment. The improvement way is to shorten the oxidation time or transform the atmosphere. In order to form an good adhesion and thin film.

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