7075铝合金化学镀对镍磷合金镀膜组织和性能的影响

Effect of electroless for 7075 aluminum alloy on microstructure and properties of Ni-P alloy coatings

金属表面处理直接影响7075铝合金的力学性能及耐腐蚀性能。以7075-T6铝合金为基体,采用化学镀(EN)技术在光滑基体表面均匀镀覆一定厚度的镍磷(Ni-P)镀膜,镀膜厚度分别为3.64、5.87和7.33μm,并通过扫描电子显微镜(SEM)、X射线衍射(XRD)、硬度测试及电化学工作站等手段分析膜层特性及膜厚对7075-T6铝合金力学和腐蚀性能的影响。结果显示,化学镀镍可以在7075铝合金表面形成Ni-P镀膜,由SEM观察,Ni-P镀膜与铝合金基体结合紧密;经由XRD分析,该镀层为微晶状态;通过Rockwell-C压痕试验法可观察到镀膜具有良好的附着力。在力学性能方面,由于Ni-P镀膜的存在,除疲劳强度略有下降、伸长率下降较为明显外,硬度、屈服强度、抗拉强度和弹性模量都有明显改善。在耐腐蚀性研究方面,Ni-P镀膜的存在使基体表面耐腐蚀能力提高1个数量级,显著改善了7075-T6铝合金材料表面耐腐蚀性,能够较完好地保护基体材料。

Surface treatment directly affects mechanical properties and corrosion resistance of 7075 aluminum alloy. The base material used in the experiment was 7075-T6 aluminum alloy, the Ni-P coating with a certain thickness was fabricated by electroless nickel(EN) on the surface of smooth substrate surface, and the coating thicknesses were 3.64, 5.87 and 7.33 μm, respectively. The effect of characteristics and thickness of the coating on mechanical and corrosion properties of 7075-T6 aluminum alloy was analyzed using methods such as scanning electron microscope(SEM), X-ray diffraction(XRD), hardness test and electrochemical workstation. The experimental results showed that electroless nickel plating could form Ni-P layer on the surface of 7075 aluminum alloy, and the Ni-P coating was observed by SEM, which was tightly bonded to the substrate. The XRD analysis showed that the coating presented a microcrystalline morphology, and the coating showed good adhesion through observation by Rockwell-C indentation test. In terms of mechanical properties, the fatigue strength decreased slightly, and the elongation decreased more obviously, while the hardness, yield strength, tensile strength and elastic modulus were significantly improved. In terms of corrosion resistance, the Ni-P coating could significantly improve the corrosion resistance of the surface for 7075-T6 aluminum alloy by one order of magnitude, and the base material can be better protected.