电沉积方式对铌表面熔盐渗硅的影响

Effects of different electrodeposition methods on siliconizing of niobium in molten salt

采用由氯化钠、氯化钾、氟化钠和二氧化硅(摩尔比为1∶1∶3∶0.3)组成的熔盐,分别以直流、单脉冲、换向脉冲的电沉积方式在纯铌表面渗硅。对比研究了不同电沉积方式下所得渗硅层的厚度、成分、组织、相结构和抗氧化性。结果表明,渗硅层厚度按照单脉冲、换向脉冲、直流电沉积的方式依次降低。与直流和单脉冲电沉积相比,换向脉冲方式所得渗硅层的组织更加致密、平整。电沉积方式对渗硅层的相结构无影响,所得渗硅层均由单相Nb Si2组成,并在(110)和(200)晶面上择优生长。换向脉冲方式制备的渗硅层抗高温氧化性能最好。

Pure niobium was siliconized by direct current, single pulse current, and pulse reverse current electrodeposition in a molten salt comprising NaC1, KC1, NaF, and SiO2 at a molar ratio of 1：1：3：0.3. The thickness, composition, structure, phase, and oxidation resistance of the siliconized layers obtained by different electrodeposition methods were comparatively studied. The results showed that the thickness of siliconized layers is in the following descending order： single pulse current electrodeposition 〉 pulse reverse current electrodeposition 〉 direct current electrodeposition. The siliconized layer electrodeposited by pulse reverse current possesses a more compact and smoother morphology as compared with those obtained by direct current and single pulse current electrodeposition methods. The phase structure of the siliconized layer is not influenced by electrodeposition method and all the siliconized layers consist of single-phase NbSi2 with （110） and （200） preferred orientation. The siliconized layer deposited by pulse reverse current has the best high-temperature oxidation resistance.