Mo含量对CoCrFeNiMo高熵合金组织及耐蚀性能的影响

Effect of Molybdenum Content on Microstructure and Corrosion Resistance of CoCrFeNiMo High Entropy Alloy

高熵合金由于具有优异的机械性能及耐蚀性能在涂层工业领域备受关注。采用同步送粉激光熔覆技术在Q235钢表面制备了CoCrFeNiMox高熵合金涂层,研究了涂层的组织结构和耐蚀性能,并结合第一性原理计算分析了涂层耐蚀机理。研究结果表明:CoCrFeNiMo0.1、CoCrFeNiMo0.2高熵合金涂层是由fcc相组成,而CoCrFeNiMo0.3高熵合金涂层则由fcc相和σ相组成。合金的晶粒主要呈树枝晶,枝晶间富集Cr、Mo元素,枝晶内富集Co、Fe元素。在3.5%(质量分数)NaCl溶液中,CoCrFeNiMox高熵合金涂层具有优良的综合耐蚀性能;并且随着Mo元素含量的增加,涂层的腐蚀电位正移,腐蚀电流密度减少,钝化区间变长,阻抗弧半径增大,电极反应阻力增强。通过第一性原理计算证明,涂层较高的耐蚀性能与表面致密的钝化膜形成密切相关。

High entropy alloys have been extensively paid attention in the coating industry due to their excellent mechanical properties and corrosion resistance.CoCrFeNiMoxhigh-entropy alloy coatings were prepared on the surface of Q235 steel by laser cladding with synchronous powder feeding.The microstructure,microhardness and corrosion resistance of the coatings were studied.The corrosion mechanism of the alloys was analyzed and the strengthening mechanism of their corrosion resistance was revealed combined with the first-principle calculation.The results show that CoCrFeNiMo0.1 and CoCrFeNiMo0.2 are composed of the fcc phase.The fcc phase and tetragonal CrMo phase are both observed in the CoCrFeNiMo0.3 high-entropy alloy layer.The microstructure of the alloys is composed of dendrites.Cr and Mo elements are enriched in the interdendritic,and Co and Fe elements are enriched in the dendrites.CoCrFeNiMoxhigh-entropy alloys have excellent comprehensive corrosion resistance in 3.5%(mass fraction)NaCl solution.As the content of Mo increases,the corrosion potential shifts to more positive potentials,the corrosion current density decreases,the length of polarization region increases,the impedance arc radius increases,and the electrode reaction resistance increases.It is found via the first-principle calculation that the higher corrosion resistance of the coating is related to its dense passivation film.