电镀铝+热处理扩散工艺是制备阻氚涂层的常用方法,铝镀层表面微观形貌影响后续热处理效果,进而对阻氚性能有着重要影响.在AlCl3-1-乙基-3-甲基咪唑(1-Ethyl-3-methylimidazolium Chloride,EMIC)离子液体中,采用不同工艺参数在316L不锈钢基体表面制备铝镀层.利用X射线衍射(X-ray Diffraction,XRD)、扫描电子显微镜(Scanning Electron Microscopy,SEM)等手段,分析不同工艺参数对铝镀层相结构及内部微观形貌的影响机理.XRD结果表明:所有镀层成分均为单质铝;SEM结果表明:镀层表面部分晶粒随直流电流密度而增大,较优电流密度范围为10～20 mA·cm-2;与直流电沉积工艺相比,单向脉冲电流波形电沉积所得铝镀层厚度最大,双向脉冲电流形成铝镀层晶粒和厚度最小,晶粒大小均匀.主要原因在于,单向脉冲模式下瞬时峰值电流较大,促进镀层晶粒生长,厚度变厚;双向脉冲模式中的反向电流可溶解掉部分镀层,明显抑制镀层内较大晶粒长大,导致所形成镀层晶粒均匀细小.
Effect of different current types on the microstructure of electrodeposited aluminium coatings
[Background]Tritium permeation leakage exists in fusion reactor such as International Thermonuclear Experimental Reactor(ITER),which leads to a series of problems such as fuel loss and environmental pollution,etc.Al2O3 coating is a hot research topic for preventing tritium permeation.The preparation of Al2O3 coatings on the surface of materials is an effective way to solve this problem.Electrodeposition of Al and heat treatment diffusion technology is a common method to prepare tritium-resistant coatings.The relevant parameters during the preparation process have important effects on the microstructure and tritium-resistant performance of Al coatings.[Purpose]This study aims to analyse the mechanism of the effect of different electrodeposition process parameters on the phase structure and internal micro-morphology of aluminium coatings,and to obtain good quality aluminum coatings.[Methods]Firstly,the aluminum coating was prepared on the surface of 316L stainless steel substrate at room temperature with 316L stainless steel as cathode,aluminum wire(99.99%purity)as anode,and AlCl3-1-Ethyl-3-methylimidazolium Chloride(EMIC)ionic liquid as plating solution.Then,the changes of surface and cross section morphology of aluminum coating were observed by changing the current density under direct current mode whilst the plating time(60 min)was fixed,and the difference of the microstructure of the aluminum coating prepared under the three current modes,i.e.,direct current(15 mA·cm-2),unidirectional pulse and bidirectional pulse current,was compared.Both the X-ray diffraction(XRD)and scanning electron microscopy(SEM)were employed to characterize the phase structure and internal microstructure of aluminum coatings.[Results]The experimental results show that the coatings are all composed of Al element and have a face-centered cubic structure,in which the preferred orientation of the crystal faces of the direct current and bidirectional pulsed electrodeposition coatings is different.In the direct current mode,some grains on the coating surface increase with the increase of direct current density,and the optimal current density of direct current electrodeposition ranges from 10～20 mA·cm-2.Compared with the direct current electrodeposition process with similar parameters,under the condition of the same current density and electroplating time,the grain size of the coating microstructure obtained by pulsed current and bidirectional pulse electrodeposition is more uniform,and the grain size after bidirectional pulse electrodeposition is smaller,and the thickness of the aluminum coating obtained by unidirectional pulse current waveform electrodeposition is the largest.The grain and thickness of aluminum coating formed by bidirectional pulse current are the smallest and the grain size is uniform.[Conclusions]The introduction of pulse current has a significant effect on the size and uniformity of particles on the surface of aluminum coating.The coating obtained by pulse current is relatively dense,the grain thinning phenomenon is obvious,and the grain size is relatively uniform.The reason is that the large instantaneous peak current can inhibit the excessive growth of the grain and play a leveling role,so as to further improve the micro-morphology of the coating and improve the quality of the coating.
Tritium-resistant coatingAlCl3-EMIC ionic liquidRoom temperature aluminium platingCurrent typeMicrostructure
NETL
NSTL
万方数据
