ELECTROCHEMICAL IMPEDANCE OF HOT CORROSION OF SPUTTERED CoCrAlY COATING ON Ni_3Al And Ni_3Al－Fe INTERMETALLICS

采用电化学交流阻抗技术并结合物相分析技术研究了溅射ＣｏＣｒＡｌＹ涂层对Ｎｉ３Ａｌ、Ｎｉ３Ａｌ－Ｆｅ金属间化合物在７００℃熔融（Ｎａ，Ｌｉ，Ｋ）２ＳＯ４中腐蚀行为的影响．结果表明，Ｎｉ３Ａｌ和Ｎｉ３Ａｌ－Ｆｅ的耐熔融盐腐蚀性能较差，其交流阻抗Ｎｙｑｕｉｓｔ图高频端表现为一曲率半径很小的圆弧，低频端为一直线，腐蚀反应受氧化剂的扩散所控制；施加ＣｏＣｒＡｌＹ涂层后，Ｎｙｑｕｉｓｔ图则呈双容抗特征，发生了沿涂层缺陷的腐蚀；提出了交流阻抗模型并解析了其中的参数．

ELECTROCHEMICAL IMPEDANCE OF HOT CORROSION OF SPUTTERED CoCrAlY COATING ON Ni_3Al And Ni_3Al-Fe INTERMETALLICS

The electrochemical impedance combined with physical analysis techniques was employed to study the effect of sputtered CoCrAlY coating on hot corrosion of Ni3Al and Ni3Al-Fe intermetallics. It is shown that Ni3Al and Ni3Al-Fe suffer severe hot corrosion, and their Nyquist diagrams are composed of a semicircle at high frequency portion and a line at low frequency portion, which means the diffusion-controlled reaction.The Nyquist plots of sputtered CoCrAlY coating are composed of two capacitive loops, which means the pitting corrosion. Equivalent circuits to interprete the features of the impedance are proposed, and the parameters in the equivalent circuits are also calculated.