AZ91D镁合金表面Ni-SiC复合镀层的制备及其性能研究

发布时间：2018-11-03 15:51

【摘要】：镁合金重量轻、比强度高,在航天、军工和电子行业的应用受到广泛关注,如何获得耐蚀、耐磨性高的镁合金是镁合金的研究热点。本文通过向镁合金活化液中添加微量Cu2+来改善镁合金电沉积预处理工艺,进而采用脉冲电沉积的方法在镁合金表面制备Ni-SiC复合镀层,对脉冲电沉积工艺参数进行优化,并研究了Ni-SiC复合镀层的硬度、耐蚀性和耐磨性。以化学镀Ni作为镁合金的电沉积预处理,随后,将化学镀镍后的镁合金置于酸性瓦特镀液中进行直流电沉积Ni,获得的Ni镀层表面粗糙度较大,镀层与基体结合力差,出现局部开裂,且镀层表面出现一些龟裂纹。其次,采用碱式预镀铜作为镁合金电沉积预处理工艺,并优化了在镁合金表面碱式预镀Cu的工艺,将预镀Cu后的镁合金在酸性瓦特镀液中进行直流电沉积,得到了结构完整的Ni镀层,说明碱式预镀Cu处理对镁合金起到了有效的保护作用。采用脉冲电沉积在镁合金表面制备Ni-SiC复合镀层,对复合镀层的微观形貌、成分和性能进行分析,所获得Ni-SiC复合镀层表面结构完整,SiC颗粒均匀地分布于Ni基质镀层中;随着复合镀液中SiC添加量的增加,复合镀层中的SiC含量升高,镀层的硬度、耐蚀性、耐磨性均呈现先提高后下降的趋势,当镀液中SiC的添加量为40 g/L时,复合镀层的耐蚀性、耐磨性达到最佳。以脉冲电流的占空比为单因素变量,探究了脉冲电流占空比对镁合金表面脉冲电沉积Ni-SiC复合镀层的微观形貌、成分及性能的影响,研究表明,当脉冲占空比为50%时,所制备的Ni-SiC复合镀层SiC含量最高,镀层的硬度、耐蚀、耐磨性均达到最佳。
[Abstract]:Magnesium alloys are light in weight and high in specific strength. The applications of magnesium alloys in aerospace, military and electronic industries have been widely concerned. How to obtain corrosion resistant magnesium alloys with high wear resistance is a hot research topic of magnesium alloys. In this paper, the pretreatment process of magnesium alloy electrodeposition was improved by adding trace Cu2 to magnesium alloy activation solution, and then Ni-SiC composite coating was prepared on magnesium alloy surface by pulse electrodeposition, and the parameters of pulse electrodeposition were optimized. The hardness, corrosion resistance and wear resistance of Ni-SiC composite coating were also studied. The electroless Ni was used as the electrodeposition pretreatment of magnesium alloy, and then the electroless nickel plated magnesium alloy was placed in acid watt bath for direct current electrodeposition (Ni,). The surface roughness of the Ni coating was larger, and the adhesion between the coating and the substrate was poor. There are local cracks and some tortoise cracks on the coating surface. Secondly, the basic pre-copper plating was used as the pretreatment process of magnesium alloy electrodeposition, and the process of basic pre-plating of Cu on magnesium alloy surface was optimized. The magnesium alloy after pre-plating Cu was deposited in acid Watt bath. The Ni coating with complete structure was obtained, which shows that the basic preplating Cu treatment has an effective protective effect on magnesium alloy. The Ni-SiC composite coating was prepared on magnesium alloy surface by pulse electrodeposition. The microstructure, composition and properties of the composite coating were analyzed. The surface structure of the Ni-SiC composite coating was complete and the SiC particles were uniformly distributed in the Ni matrix coating. With the increase of SiC content in the composite plating bath, the content of SiC in the composite coating increased, and the hardness, corrosion resistance and wear resistance of the coating increased first and then decreased. When the addition of SiC in the bath was 40 g / L, The corrosion resistance and wear resistance of the composite coating are the best. With the duty cycle of pulse current as a single factor variable, the effects of pulse current duty ratio on the microstructure, composition and properties of pulsed electrodeposition Ni-SiC composite coating on magnesium alloy surface were investigated. The results showed that when the pulse duty ratio was 50, the effect of pulse duty ratio on the microstructure, composition and properties of Ni-SiC composite coating was investigated. The Ni-SiC composite coating has the highest SiC content and the best hardness, corrosion resistance and wear resistance.
【学位授予单位】：西安科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG174.4

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