商用鎳基超合金之電化學腐蝕行為研究

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Title:	商用鎳基超合金之電化學腐蝕行為研究
Authors:	鄭沂聖
Contributors:	材料科學與奈米科技研究所
Keywords:	鎳基超合金孔蝕臨界孔蝕溫度陽極極化
Date:	2010
Issue Date:	2011-10-27 15:47:52 (UTC+8)
Abstract:	本研究在探討鎳基超合金(HD205)在三極式電化學系統在除氧環境下對不同種類、濃度及溫度的氯鹽電解液之腐蝕影響，主要包含鎳基超合金經過電化學腐蝕後的表面形態變化、臨界孔蝕溫度(critical pitting temperature CPT)以及極化曲線(孔蝕電位(Epit))的探討，電解液內的金屬離子與氯離子，對於孔蝕有明顯的影響，因此並更進一步探討電解液內金屬離子與氯離子對孔蝕(pitting)影響。在實驗過程中，利用不同濃度的氯鹽電解液，分別為0.1、0.25、0.5和1 M的氯化鈉、氯化銨及氯化鐵不同電解液，在定電流0.5 mA中進行，測得鎳基超合金(HD205)臨界孔蝕溫度，無論在何種電解液中當提升其中氯鹽濃度，可觀察到當濃度越高所得到臨界腐蝕溫度越低。接著再以不同溫度在固定的電解液濃度下，分別測量鎳基超合金(HD205)的極化曲線，並可得知當溫度越高所得的孔蝕電位(Epit)越低；藉由SEM圖結果可以得知，氯鹽電解液內的金屬離子與氯離子濃度越高，鎳基超合金(HD205)的孔蝕破壞程度越明顯，由此可知Na+、NH4+、Fe3+與氯離子對鎳基超合金(HD205)的腐蝕影響具有重要的關係。 This study investigated the corrosion effects of nickel-base superalloys (HD205) in the electrochemical three-electrode system with deaerated environment on the different cation types , chloride concentration and temperature of the aqueous electrolyte, mainly containing the surface morphology, critical pitting temperature (CPT) and the anodic polarization curve (pitting potential ,Epit ) of the electrolyte inside the metal ions and chloride ions, pitting corrosion for significant impact and, therefore, more further explore the metal ions within the electrolyte and chloride ions on pitting corrosion. By using different concentrations of chloride electrolyte 0.1, 0.25, 0.5 and 1 M sodium chloride, respectively with a determined parameter, the result shows that regardless of the electrolyte which was used, we found that the higher concentration of sodium choloride in the electrolyte, the lower critical corrosion temperature we obtained. At different temperatures and fixed electrolyte concentrations were measured in nickel-based superalloy (HD205) of the polarization curves, we can observe that the higher temperature is, the lower pitting potential (Epit) we got. from SEM graph we can see that the higher concentration of chloride ion on the nickel-based superalloy (HD205), the more obvious damage, can be found. Therefore, we found that the concentration of metal and chloride ions on the nickel-based superalloy (HD205) have played a very important relationship on surface corrosion.
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