TiAlN/CrN多层膜的组织结构及耐蚀性机理

Microstructure and Corrosion Resistance Mechanism of TiAlN/CrN Multilayer Coatings

目的研究TiAlN/CrN多层膜及TiAlN、CrN单一膜层的微观组织和电化学性能区别,分析不同结构薄膜材料的耐腐蚀性影响因素。基于电化学参数、组织结构和腐蚀形貌特征,为开发新型腐蚀性薄膜提供理论依据。方法采用多弧离子镀方法,在316不锈钢基底上先沉积150 nm Cr薄膜作为过渡层,然后交替沉积CrN薄膜和TiAlN薄膜,制备单层厚度为10 nm的TiAlN/CrN多层膜。作为对比,制备单一TiAlN、CrN薄膜。通过SEM、XRD表征薄膜断面形貌、组织结构,并分析耐蚀机理,结合极化曲线和阻抗谱对三种涂层进行电化学性能分析,最后对涂层进行浸泡腐蚀试验。结果TiAlN/CrN纳米多层膜为面心立方结构,呈现共格外延生长,且呈(200)择优取向。纳米多层膜的动电位极化曲线测量结果与不锈钢基体和单层薄膜相比,其腐蚀电位正移为−0.36 V,腐蚀电流密度降低为0.501μA/cm^2,极化电阻为120 kΩ·cm^2。阻抗谱试验结果表明,相比较于单层膜和基体,TiAlN/CrN多层膜的CPE值最低,为29.83×10^−6Ω^−1·cm^−2·sn,n值为0.922,电阻为1.50×10^6Ω·cm^2。腐蚀形貌分析可得出,多层薄膜腐蚀后表面形貌与沉积态涂层形貌最为接近,认为其具有较高的耐腐蚀性。结论纳米层状结构改变了单一薄膜的原始生长模式,抑制了粗大柱状晶的生长,减小了薄膜的固有缺陷、晶粒尺寸,对薄膜的耐蚀性有正面积极的作用。

The work aims to study the difference in microstructure and electrochemical properties of multilayer coating(TiAlN/CrN)and single coating(TiAlN and CrN)and analyze the corrosion resistance factors of coatings with different structures,to provide theoretical reference for the development of new anti-corrosive coatings based on the characteristics of electrochemical parameters,microstructure and corrosion morphology.150 nm Cr coating was deposited on 316 stainless steel substrate with multi-arc ion plating as the transition layer.Then,CrN and TiAlN coatings were deposited alternately to prepare the TiAlN/CrN multilayer coatings with a thickness of 10 nm.Finally,CrN and TiAlN coatings were prepared for contrast.The cross-sectional morphology and microstructure of coatings were characterized by SEM and XRD and the corrosion resistance mechanism was analyzed.Combined with polarization curves and impedance spectrum,the electrochemical properties of three coatings were tested and immersion corrosion test was carried out to the coatings.The TiAlN/CrN multilayer coating exhibited a face centered cubic structure and showed co-extensive growth and(200)preferred orientation.Through the comparison of measurement results of potential polarization curves for the multilayer coating,stainless steel substrate and single coating,the corrosion potential of multilayer coating shifted positively to−0.36 V,the corrosion current density decreased to 0.501μA/cm^2 and the polarization resistance was 120 kΩ·cm^2.In terms of EIS,TiAlN/CrN multilayer coating possessed the lowest value of CPE(29.83×10^−6Ω^−1·cm^−2·sn),n of 0.922 and resistance of 1.50×10^6Ω·cm^2,compared with stainless steel substrate and single coating.Furthermore,the corrosion morphology of multilayer coating was closed to the morphology of as-deposited coating.Therefore,the TiAlN/CrN multilayer coating exhibited superior corrosion resistance.Nano-layered structure changes the original growth mode of single coating,inhibits the growth of coarse columnar crystals,reduces the inherent defects and grain size of the coating,and plays a positive role in the corrosion resistance of the coating.