Al-Ni 复合涂层的结合强度及耐蚀性能研究

Bonding Strength and Corrosion Resistance of Al-Ni Composite Coatings

目的研究冷喷涂Al-Ni复合涂层的结合强度和耐蚀性能,尝试通过在Q345R钢材表面制备防护涂层的方法来改善Q345R钢的服役寿命。方法采用冷喷涂技术在Q345R板材表面制备纯Al涂层和Al-Ni复合涂层,利用SEM观察、拉伸试验、腐蚀质量损失试验和EIS测试等技术,测试与分析涂层的结合强度和耐蚀性能,研究Ni粉的含量对涂层的孔隙率、显微组织、涂层–基体间结合强度和耐蚀性能的影响规律。结果涂层与Q345R钢结合良好,在500倍电子显微镜下,界面处没有观察到明显的孔洞与裂纹。由于Ni颗粒的夯实作用,Al-Ni复合涂层的致密性有所提高。相比纯Al涂层,Al-10Ni复合涂层的界面结合强度有略微提升,断裂失效形式为典型的界面粘结断裂。Al-15Ni复合涂层的界面结合强度提升明显,其强度为31 MPa。腐蚀结果显示,纯Al涂层和Al-Ni复合涂层的腐蚀质量损失率较基体材料Q345R钢都明显降低,耐蚀性能有所提升。其中纯Al涂层的耐蚀性最好,腐蚀质量损失率为0.26 g/(cm^(2)·a),而Q345R基体的腐蚀质量损失率为2.95 g/(cm^(2)·a)。结论冷喷涂Al-Ni复合涂层与基体结合良好,其耐蚀性优于Q345R基体,可为基体提供保护作用,其中Ni颗粒的质量分数为15%时,涂层的结合强度和耐蚀性综合性能最好。

With the basic equipment of national economic development,pressure vessel is widely used in the sector of petroleum,chemical,energy and other industries.However,due to the complex working environment,the surface of the equipment is easy to generate mechanical scratches,corrosion and wear defects,which affect the service life of the plate.As a rapid prototyping technology characterized by low temperature and solid deposition of powder,cold spraying technology has been widely used in additive manufacturing,anti-corrosion coating preparation,repair and remanufacturing.In this paper,pure Al coating and Al-Ni composite coating are prepared on the surface of Q345R steel by adding different contents of Ni powder in cold spraying Al powder.The influence of Ni powder particles in terms of the bonding strength and corrosion resistance of the coatings is systematically studied.Pure Aluminum,Al-10wt.%Ni,Al-15wt.%Ni and Al-20wt.%Ni coatings(The following was called Al coating and Al-10Ni,Al-15Ni,Al-20Ni composite coatings)are prepared by cold spraying on Q345R substrate.The microstructure,porosity,bonding strength and corrosion resistance of the coating are tested by SEM observation,XRD analysis,tensile test,electrochemical test and weight loss test.The results show that the plastic deformation of Al particles increases and the porosity of the coating decreases due to the tamping of Ni particles.With the increase of Ni particles content,the coating becomes more compact.The porosity of Al coating and Al-10Ni,Al-15Ni,Al-20Ni composite coatings are 5.8%,1.5%,1.0%and 0.8%.The bonding strength of Al coating and Al-10Ni,Al-15Ni,Al-20Ni composite coatings are 14.6,15.2,31.0 and 22.0 MPa.During the deposition process,the impact of Ni particles makes the interface bonding area between the coating and the substrate become bigger.On the other hand,some Ni particles embedded in the surface of the substrate have a pinning effect on the interface between the coating and the substrate,and these conditions are favorable for increasing the bonding strength.Corrosion weight loss test and electrochemical test are used to evaluate the corrosion resistance of the coating.The conventional three-electrode system is used in the experiment,and the scanning frequency is 0.01~105 Hz.The samples are encapsulated with epoxy resin,and the 3.5%sodium chloride solution is for test.According to the actual application environment of Q345R steel,the solution is added with acetic acid to adjust the pH value to 2.8.It can be found that the corrosion weight loss rates of Q345R steel substrate,pure Al coating,Al-10Ni,Al-15Ni and Al-20Ni composite coatings are 2.95,0.26,2.38,1.32 and 1.34 g/(cm^(2)·a).The corrosion weight loss rate of the four coatings is lower than that of Q345R steel,which indicates that both pure Al coating and Al-Ni composite coating can effectively protect the substrate material.However,compared with pure Al coating,the corrosion weight loss rate of Al-Ni composite coating increases possibly due to the existence of potential difference between Al element and Ni element in Al-Ni composite coating,which is easy to form galvanic corrosion and promotes the corrosion of Al element in the composite coating.Zview software is used to fit the electrochemical test results,and the electrochemical test results are consistent with the conclusion of corrosion weight loss test.Compared with Q345R substrate,pure Al coating and Al-Ni composite coating have better corrosion resistance,which can effectively prevent the corrosive medium from contacting directly with the substrate and prevent the substrate from being corroded.In practical engineering applications,Q345R steel has high requirements for comprehensive indicators of corrosion resistance and bond strength.This paper systematically compares the bonding strength and corrosion resistance of composite coatings with nickel content of 10%,15%and 20%.The results show that when nickel content is 15%,the composite coating has the best bonding strength and corrosion resistance,which provides data to evidence the preparation of protective coatings for pressure vessels.