Hardening effect induced by incorporation of SiC particles in nickel electrodeposits
Hardening effect induced by incorporation of SiC particles in nickel electrodeposits
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DOI：
10.1007/s10800-005-9082-y
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发表时间：
2006-04-01
影响因子：
2.9
通讯作者：
Spyrellis, N
中科院分区：
文献类型：
--
作者：
Pavlatou, EA;Stroumbouli, M;Spyrellis, N
在无添加剂的瓦茨型镀液中，在直流和脉冲电流条件下制备了含微米和纳米碳化硅颗粒(分别为1微米和20 nm)的纯镍和镍基复合电镀层。研究了碳化硅颗粒尺寸、共沉积率和外加电流类型对镀层显微硬度的影响以及对镀层组织结构的影响。无论是在直流条件下还是在脉冲电流条件下制备的Ni/SiC复合镀层相对于纯Ni镀层都表现出了显著的强化效果。复合镀层硬度的提高与碳化硅颗粒表面吸附H+引起镍微晶的特殊结构变化有关，从而导致了镍晶体生长的(211)织构模式。脉冲电沉积显著提高了镍/碳化硅复合镀层的硬度，特别是在低占空比条件下，晶粒细化和较高的碳化硅含量(体积分数)。%)。与Ni/微米碳化硅复合材料相比，Ni/纳米碳化硅涂层硬度的提高归因于随着颗粒尺寸的减小，镶嵌在镍基中的碳化硅颗粒数密度增大。此外，观察到的碳化硅颗粒的硬化效果可能与其不同的包埋机制有关，对于微米级的碳化硅颗粒，可表现为晶间结合，而对于纳米碳化硅颗粒则表现为部分晶内结合。
Pure Ni and nickel matrix composite electrocoatings containing micron- and nano-SiC particles (1 mu m and 20 nm respectively) were produced under direct and pulse current conditions from an additive-free Watts type bath. The effect of the particle size, codeposition percentage of SiC and type of imposed current on the microhardness as well as on the microstructure of the electrodeposits were investigated. Ni/SiC composite deposits prepared under either direct or pulse current conditions exhibited a considerable strengthening effect with respect to pure Ni coatings. The improved hardness of composite coatings was associated to specific structural modifications of Ni crystallites provoked by the adsorption of H+ on the surface of SiC particles, thus leading to a (211) texture mode of Ni crystal growth. Pulse electrodeposition significantly improved the hardness of the Ni/SiC composite coatings, especially at low duty cycles, in which grain refinement and higher SiC incorporation (vol. %) was achieved. The enhanced hardness of Ni/nano-SiC deposits, as compared to Ni/micron-SiC composites, was attributed to the increasing values of the number density of embedded SiC particles in the nickel matrix with decreasing particle size. In addition, the observed hardening effects of the SiC particles might be associated to the different embedding mechanisms of the particles, which could be characterized as inter-crystalline for micron-SiC and partially intra-crystalline for nano-SiC particles.