高熵合金FeCoCrNiMox 在氫氟酸及氟鹽水溶液中之電化學腐蝕研究

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Title:	高熵合金FeCoCrNiMox 在氫氟酸及氟鹽水溶液中之電化學腐蝕研究 Studies on the electrochemical corrosion of high-entropy FeCoCrNiMox alloys in Hydrofluoric Acids and Fluoride Salts
Authors:	楊敦勝
Contributors:	化學工程與材料工程學系奈米材料碩士班
Keywords:	高熵合金極化曲線 high-entropy alloy anodic polarization curves
Date:	2019
Issue Date:	2019-09-18 13:24:35 (UTC+8)
Abstract:	本論文旨在研究高熵合金FeCoCrNiMox(x=0, 0.3, 0.7, 1.0)在氫氟酸及氟鹽中的電化學腐蝕特性，此成分與一般市面上的316不鏽鋼相近，鐵(Fe)為鋼鐵合金常見的主要成分，而添加鉻(Cr)有助於鈍態膜的形成，而添加鉬(Mo)可以有效抗氯鹽孔蝕，而尋找出與氟鹽反應後的不同之處。由XRD分析結果，當-Mo含量為0和0.3時為單一FCC相，-Mo含量≧0.7時，則有HCP相大量出現。隨著Mo含量增加而逐漸增加，並使用使用微硬度試驗機檢測不同成分合金的硬度。本實驗以恆電位儀測量四種合金，在氫氟酸與氟化納分別為各三種濃度( 0.01M、0.1M、1M )溶液中進行陽極極化曲線測試，來測定合金與溫度相關之腐蝕電位(Ecorr)、腐蝕電流密度(icorr)、鈍態電流密度(ipass)等電化學相關參數，並且比較其變化。並使用阻抗頻譜法檢測合金在酸性及氟鹽環境下的各項數據，可以獲得Nyquist圖及Bode圖，並模擬其電路圖。使用SEM觀察合金在王水腐蝕後以及陽極極化後的表面狀況，成分分析則使用EPMA獲得合金上元素的強度及分布情形。 The purpose of this research is to investigate the electrochemical corrosion characteristics of high-entropy alloy FeCoCrNiMox (x=0, 0.3, 0.7, 1.0) in hydrofluoric acid and fluoride salt. The HEA composition is similar to 316 stainless steel on the market ; the major components Fe. The addition of chromium (Cr) contributes to the formation of a passive film, and the addition of molybdenum (Mo) can effectively resist the pitting of chloride salts. It is interesting to know that the difference may find in the fluoride environments. From the results of XRD analysis, it is observed that when -Mo content between 0 and 0.3, it is a single FCC phase, and when the -Mo content is≧0.7, a large amount of HCP phase appears. As the Mo content increases, the hardness of the alloys is increased unequivocally using a microhardness tester. In this experiment, four kinds of alloys were prepared by arc melting and electrochemically measured by a potentiostat. Anodic polarization curves were obtained in hydrofluoric acid and its sodium salt in three concentrations (0.01M, 0.1M, 1M) to determine all relevant corrosion parameters of the alloy, such as corrosion potential, corrosion current density and passive current density through the potential dynamic polarizations. Use the Electrochemical Impedance Spectroscopy(EIS) in terms of Nyquist and Bode plots to establish an equivalent circuit to simulate the interface electric double layer structures. Both SEM and EMPA were employed for the corroded surface analysis both quantitatively and qualitatively.
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