MoNiZrTiHf高熵合金在冰晶石熔盐中的腐蚀性能

Corrosion Behavior of High-entropy Alloys in Cryolite Molten Salt

采用真空电弧熔炼法制备MoNiZrTiHf高熵合金,研究其在960℃下冰晶石熔盐中的腐蚀性能。利用带有能谱仪的扫描电镜和X射线衍射仪分析高熵合金腐蚀层的形貌、成分和组织结构。结果表明:MoNiZrTiHf高熵合金在冰晶石熔盐中的腐蚀速率随时间的延长先快后慢再加快。熔盐的NaF与AlF3的分子比影响合金腐蚀性能,合金在分子比为1.8的熔盐中表现出更好的耐腐蚀性能。腐蚀过程主要为氟离子向合金内部渗透后开裂,并加速O、Al、Na等元素向合金内部扩散并且腐蚀层疏松而后脱落,表层的腐蚀产物主要为Zr、Hf的氧化物;腐蚀层中间层的产物主要为金属间化合物及金属氧氟化物。

MoNiZrTiHf high entropy alloy was prepared with vacuum electric arc melting.The corrosion behavior of the prepared high entropy alloy in cryolite composite melt at 960℃ was studied based on structure and morphology characterization and corrosion performance investigation.The experiments involved 960℃scanning electron microscopy（SEM）coupled with electron dispersive spectrometry（EDS）, X-ray diffractometry（XRD）and conventional corrosion measurements.The results show that the corrosion rate of the MoNiZrTiHf high-entropy alloy first increases,then decreases and finally increases again with the increase of corrosion time.The molecular ratio of the composite molten salt dramatically affects those corrosion resistances.Especially,the alloy exhibits best corrosion resistance in the molten salt with a molecular ratio of NaF to AlF3 of 1.8.The corrosion process consists of fluorinion penetration into the alloy internal,which lead to the diffusion acceleration of O,Al,Na and subsequent crack.Afterwards the porous corrosion layer falls off.The corrosion products of the surface layer are mainly zirconium oxide and hafnium oxide,while those of the interlayer are mainly intermetallic compounds and oxyfluoride.