沉积时间对Ni-Cr合金层组织及耐蚀性的影响

Influence of depositing time on microstructure and corrosion resistance of Ni-Cr alloyed layer

采用双辉等离子表面冶金技术在Q235低碳钢表面制备了不同沉积时间的Ni-Cr合金层。利用扫描电镜(SEM)、EDS能谱仪和X射线衍射仪(XRD)等分析了Ni-Cr合金层的组织成分,并运用开路电位、极化曲线和交流阻抗技术研究了Ni-Cr合金层的电化学腐蚀行为。结果表明,Ni-Cr合金层主要由沉积层和扩散层组成,其厚度随沉积时间增加而增加。Ni-Cr合金层的主要物相为Ni2.9Cr0.7Fe0.36相和FeNi3相。极化曲线数据表明在3.5%NaCl溶液中,3 h沉积时间下的Ni-Cr合金层具有最高的耐蚀性和最低的腐蚀速率,其保护效率和孔隙率分别为99.23%和1.18%。随着沉积时间增加,电荷转换电阻Rct逐渐增大,其腐蚀抑制能力提高。当沉积时间大于3 h时,Ni-Cr合金层的Rct增加不明显,表明沉积3 h后Ni-Cr合金层的耐蚀性提高十分有限。

Ni-Cr alloyed layers with different depositing time were prepared on the surface of Q235 steel by double glow plasma surface metallurgy technology.Microstructure and phases of the alloyed layers were characterized by means of scanning electron microscopy(SEM),energy dispersive spectrometer(EDS)analysis and X-ray diffraction(XRD).Electrochemical corrosion behavior of the Ni-Cr alloyed layers was studied by using open circuit potential,potentiodynamic polarization and electrochemical impedance spectroscopy(EIS).The results show that the Ni-Cr alloyed layers consist of a deposited layer and an inter-diffusion layer,and the thickness of the Ni-Cr alloyed layers increases with the increase of deposition time.The main phases of the Ni-Cr alloyed layers are Ni2.9Cr0.7Fe0.36 phase and FeNi3 phases.The polarization curve data shows that the Ni-Cr alloyed layer with the depositing time of 3 h has the highest corrosion resistance and the lowest corrosion rate in 3.5%NaCl solution,and the protection efficiency and porosity are 99.23%and 1.18%,respectively.As the deposition time increases,the charge conversion resistance(Rct)of the Ni-Cr alloyed layers gradually increases,and its corrosion inhibition ability is improved.When the deposition time is more than 3 h,the increment of the Rct is not obvious,which shows that the improvement of corrosion resistance of the Ni-Cr alloy layers with deposition time more than 3 h is very limited.