Corrosion behavior and surface film characterization of TaNbHfZrTi high entropy alloy in aggressive nitric acid medium
Corrosion behavior and surface film characterization of TaNbHfZrTi high entropy alloy in aggressive nitric acid medium
复制标题
DOI：
10.1016/j.intermet.2017.06.002
复制
发表时间：
2017-10-01
期刊：
影响因子：
4.4
通讯作者：
Mudali, U. Kamachi
中科院分区：
文献类型：
--
作者：
Jayaraj, J.;Thinaharan, C.;Mudali, U. Kamachi
研究了TaNbHfZrTi高熵合金（HEA）在硝酸和氟化硝酸中在常温（27 ℃）和沸腾（120 ℃）条件下的腐蚀行为。在环境条件下，在11.5 M HNO3中，合金在动电位极化过程中自发钝化。在沸腾的11.5 M HNO3中暴露240 h，腐蚀速率可忽略不计。扫描电子显微镜（SEM）研究未显示任何显著的腐蚀侵蚀。TaNbHfZrTi HEA的高耐蚀性归因于其单相bcc结构。X射线光电子能谱（XPS）分析表明，在沸腾的硝酸中形成的保护性钝化膜主要由Ta2O5组成，在空气中形成的原生膜中存在ZrO 2和HfO 2。动电位极化研究表明，在11.5 M HNO3 + 0.05 M NaF在环境条件下的HEA的伪钝化行为。在沸腾的氟化硝酸中，TaNbHfZrTi HEA的SEM图像显示出严重的腐蚀形态，表明合金元素的金属氧化物的不稳定性。XPS研究证实了ZrF4、ZrOF2和HfF4沿着Ta、Nb和Ti的非保护性氧化物在膜上的存在，导致TaNbHfZrTi HEA在氟化硝酸中的耐腐蚀性降低。
Corrosion behavior of TaNbHfZrTi high-entropy alloy (HEA) was investigated in nitric and fluorinated nitric acid at ambient (27 degrees C) and boiling (120 degrees C) conditions. The alloy passivated spontaneously during potentiodynamic polarization in 11.5 M HNO3 at ambient condition. The corrosion rate was negligible in boiling 11.5 M HNO3, exposed for 240 h. Scanning electron microscopic (SEM) studies did not show any significant corrosion attack. The high corrosion resistance of TaNbHfZrTi HEA was attributed to its single phase bcc structure. X-ray photoelectron spectroscopic (XPS) analysis revealed that the protective passive film formed in boiling nitric acid was predominantly composed of Ta2O5, in contrast to the presence of ZrO2 and HfO2 in air-formed native film. Potentiodynamic polarization studies indicated a pseudo-passivation behavior of the HEA in 11.5 M HNO3 + 0.05 M NaF at ambient condition. In boiling fluorinated nitric acid, SEM images of TaNbHfZrTi HEA displayed a severely corroded morphology indicating the instability of the metal-oxides of the alloying elements. XPS investigations confirmed the presence of ZrF4, ZrOF2 and HfF4 along with un-protective oxides of Ta, Nb and Ti on the film, resulting in decreased corrosion resistance of TaNbHfZrTi HEA in fluorinated nitric acid.