La_2O_3对铁基合金激光熔覆层耐蚀性能的影响

Effect of La_2O_3 on Corrosion Resistance of Laser Clad Ferrite-Based Alloy Coatings

通过扫描电镜(SEM)观察和X射线衍射(XRD)分析,研究了不同稀土加入量对铁基合金激光熔覆层组织形貌、相组成的影响;通过极化曲线和交流阻抗谱(EIS)的测量,研究了熔覆层的电化学性能。结果表明,加入稀土细化了熔覆层的晶粒,使组织趋向均匀;同时降低了材料的极化电位,减小了极化电流密度,降低了熔覆层在腐蚀性介质中的溶解速度,随着稀土加入量的增加,EIS曲线低频区感抗弧逐渐减小,容抗弧逐渐增大,增强了熔覆层表面在交变电流下形成钝化膜的能力。腐蚀失重实验结果表明,加入稀土改善了熔覆层表面钝化膜的抗剥落能力,不同程度上减轻了材料的腐蚀失重,提高了熔覆层的耐腐蚀能力。

The Ferrite-based alloy powders with different contents of La_2O_3 were laser-clad onto steel substrate. The microstructural features and phase structure of these coatings were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. Moreover, the electrochemical properties of the coatings were investigated by anodic polarization curves and electrochemical impedance spectroscopy (EIS). The results show that the microstructure of the coatings with La_2O_3 is refined and purified and the main phase of the coating is γ(Fe, Ni). Anodic polarization results indicate that both polarization potential and polarization current density are reduced with the addition of La_2O_3. EIS results show that, with the increasing of La_2O_3, the inductive arcs shrink and capacitive arcs expand. The inductive arc at low frequency is disappeared and fully changes to capacitive arc when the La_2O_3 addition reaches 1.2%. The corrosion weight loss experiment results show that the corrosion rate is lower and the corrosion attack is lighter in the coatings with La_2O_3 than that without La_2O_3, resulting in a substantial improvement of the corrosion resistance.