高熵合金CrNbTiVZr的微观组织及其在模拟PEMFC环境中腐蚀行为研究

Microstructure of CrNbTiVZr high-entropy alloyand its corrosion behavior in simulated PEMFC environment

采用真空电弧熔炼和热处理制备了CrNbTiVZr高熵合金,利用XRD、SEM/EDS、动电位与恒电位极化曲线测试及XPS表面分析等方法,研究了高熵合金铸态及退火后的微观组织特征以及合金在模拟PEMFC环境中的电化学腐蚀行为及其钝化膜组成。结果表明,CrNbTiVZr高熵合金的铸态和退火组织均由富集Ti、Nb元素的无序BCC相和富集Cr、V、Zr元素的Laves相组成。铸态和退火合金在模拟PEMFC阴极环境中腐蚀电流密度Icorr均比304SS不锈钢下降一个数量级,具有较好的耐蚀性和稳定性,但在阳极环境中其耐蚀性与304SS相当,其中铸态合金的稳定性较差。合金在阴极环境良好的耐蚀性主要与其表面形成由Cr2O3、Nb2O5、V2O3、Ti2O3及ZrO2组成的致密钝化膜关系密切。

CrNbTiVZr high-entropy alloy was prepared by vacuum arc melting and heating treatment.The microstructure,electrochemical corrosion behavior in simulated PEMFC environment and the composition of the passive film were investigated by XRD,SEM,XPS,potentiodynamic and potentiostatic polarization test.The results showed that the as-cast and annealed CrNbTiVZr high-entropy alloy were both composed of the disordered BCC phase enriched Ti,Nb and the Laves phase enriched Cr,V and Zr elements.The as-cast and annealed alloy both had good corrosion resistance and stability in the simulated PEMFC cathode environment due to the corrosion current density were one order of magnitude lower than that of the 304 SS,but the corrosion resistance of both alloy in the anode environment were comparable to that of the 304 SS,which the as-cast alloy had poor stability.The good corrosion resistance of the alloy in the cathode environment was mainly related to the formation of the dense passive film of Cr2O3,Nb2O5,V2O3,Ti2O3 and ZrO2.