【作者】 杨海燕；

【导师】 卫英慧；

【作者基本信息】 太原理工大学 ， 材料学， 2007， 硕士

【摘要】 化学镀Ni-Co-P合金镀层具有高密度磁性特点，由它制成的磁盘线密度大，而且膜层厚度均匀、硬度高、耐蚀性好，且操作方便，成本低，成为近年来的研究热点。但是，目前所报导的化学镀Ni-Co-P工艺存在镀速低、镀液不稳定、施镀过程中pH值变化大等问题。本研究采用复合络合剂，通过正交试验对化学镀Ni-Co-P工艺进行了优化，得出了最佳的工艺参数，并对镀层的形貌、成分、组织结构和性能进行了检测并分析了它们之间的关系；同时详细研究了热处理对化学镀Ni-Co-P合金组织结构和性能的影响。然而，化学镀三元Ni-Co-P合金一个无法回避的问题就是反应较复杂，薄膜成分不易控制，重复性不好。由于化学镀Ni-P二元合金发展历史较长，工艺成熟；且离子注入又具有注入元素可控，同时还可提高材料表面硬度、耐磨性、耐蚀性和磁性能等。因此，我们结合化学镀和离子注入这两种表面技术，在化学镀Ni-P膜中离子注Co获得Ni-Co-P薄膜，并研究了离子注Co对镀层表面形貌、组织结构和性能的影响。在正交试验的基础上优化得到的化学镀Ni-Co-P配方为：NiSO₄·6H₂O 0.1 mol·L^-1 CoSO₄·7H₂O 0.1 mol·L^-1NaH₂PO₂·H₂O 0.2 mol·L^-1 Na₃C₆H₅O₇·2H₂O 0.5 mol·L^-1 CH₃CH（OH）COOH 0.2 mol·L^-1 （NH₄）₂SO₄ 0.5 mol·L^-1 pH：9温度：80℃研究结果表明：1．化学镀Ni-P和Ni-Co-P合金为P在Ni（Co）基上的过饱和固溶体，镀层中P含量和Co含量的增加都使得“胞状”组织尺寸减小，Co的共沉积能减低镀层沉积速度，并使镀层更加致密均匀；随着镀层中Co含量的增加，镀层硬度和耐腐蚀性能提高，磁性能有从软磁特性向硬磁特性转变的趋势。2．镀态下为微晶或纳米晶结构的化学镀Ni-P和Ni-Co-P合金，处于热力学亚稳定状态；300℃热处理1h后镀层发生重结晶，晶粒细化，400℃处理后晶粒达到最小值，更高温处理晶粒长大并开始析出稳定相Ni₃P；Co的共沉积提高了Ni₃P稳定相的析出温度，还稳定了纳米晶粒尺寸，大大提高了镀层的热稳定性。3．热处理显著影响镀层性能，各镀层在400℃处理后由于具有最小晶粒尺寸，硬度达到最大值，温度继续升高，晶粒长大硬度有所下降，但500℃处理后，由于析出大量稳定相Ni₃P而硬度又有所回升；热处理对镀层磁性能影响较小；热处理后镀层耐蚀性先提高，400℃处理后耐蚀性最优异，继续提高温度耐蚀性则又有所下降；当Co含量达到27.57at．％时，由于良好的热稳定性，镀层硬度变化平稳，热处理后镀层耐蚀性稍有下降。4．化学镀Ni-P合金表面形貌为凸显“胞状”结构，离子注Co后表面变得较平整，“胞”结合更加紧密，Co在化学镀Ni-P膜中呈梯度分布，镀层中Co含量和注入深度随注入剂量的增加而增加。5．化学镀Ni-P合金为纳米晶结构，离子注入Co后镀层晶粒明显长大，且析出大量Ni₃P，在结合面形成了Cu-Ni合金；当注入剂量增加至5×10¹⁷ions·cm^-2时，镀层表面形成氧化膜。6．离子注Co可提高化学镀Ni-P镀层硬度，但幅度不大，最大可提高6％；离子注Co后镀层矫顽力H_c、饱和磁化强度M_s和耐腐蚀性能都明显提高，且随着注入剂量的增加而增加。更多还原

【Abstract】 In recent years, many studies were carried out to develop the electroless Ni-Co-P alloy for numerous interests such as good magnetic performance of high line density, uniform thickness, high hardness, good corrosion resistance, easy operation and low cost. However, some problems of the present reported electroless Ni-Co-P process have to be solved urgently, such as low deposition rate, low stability and great variation of pH during plating. In this study, the electroless Ni-Co-P plating was stabilized using complexing agents, sodium citrate and lactic acid. Moreover, the electroless Ni-Co-P process was optimized by orthogonal experiment and the optimal operating conditions were obtained. The surface morphology, chemical composition, microstructure and properties of the coating were investigated and the relationship among them was analyzed. The effect of heat treatment on the microstructure and properties of the coating were also studied.It is an avoidless problem of the electroless Ni-Co-P alloy that the chemical compositions of the coatings are difficult to be controlled for its complex reaction. However, the electroless Ni-P process have been studied for a long time, and the quantity of the ions can be controlled well by ion implantation technology. In addition, ion implantation has been widely used for a valuable surface modification to improve the near-surface properties, such as surface hardness, wear and corrosion resistance and magnetism of various metals. Therefore, ion implanted Ni-Co-P alloy was obtained by combining the electroless plating and the ion implantation technology, i.e. Co ions were implanted into the electroless Ni-P alloy by ion implantation technology. The effect of Co ion implantation on the surface morphology, microstructure and properties were discussed.Based on the orthogonal experiment, the optimal electroless Ni-Co-P alloy bath is obtained as follows: The experimental observations show:1. The electroless Ni-P and Ni-Co-P alloy is a supersaturated solid solution of P dissolved in Ni （Co） matrix. The size of the "cell" decreased with the increase of the P or Co content in the coatings. Co co-deposition decreased the deposition rate and improved the density of the coatings. With the increase of the Co content, the hardness and corrosion resistance increased and a trend from soft to hard magnetism was observed.2. The as-plated Ni-P and Ni-Co-P alloy with microcrystalline or nanocrystalline structure is metastable. When heat treated for one hour at 300℃, recrystallization occurred and grain size refined, and the grain size decreased with temperature for one hour up to the minimum at 400℃. The grains begin to grow and the Ni₃P separate when heat treated for one hour at higher temperature. Thermostability is improved greatly by Co co-deposition for higher Ni₃P precipitation temperature and stabilizing the grain.3. Obviously, the properties of the coating are affected by heat treatment. The hardness increased with heat treatment temperature at 400℃up to a maximum and decreased with higher temperature. However, the hardness increased again when heated at 500℃because of many equilibrium Ni₃P precipitates. Heat treatment has a little effect on magnetism. Corrosion resistance increased with heat treatment temperature at 400℃up to the best and decreased with higher temperature. When the Co content is up to 27.57at.%, the hardness change placidly and heat treatment caused a little decrease in corrosion resistance because of good thermostability.4. After Co ion implantation, the surface morphology of electroless Ni-P alloy with "cell" structure become more and more smooth, dense and the grains attached each other. A gradient profile of Co content in the electroless Ni-P alloy is found. The Co content and ion implantation depth increased with the increase of the fluence.5. The as-plated Ni-P alloy has a nanocrystalline structure. After Co ion implantation, the grains grow, Ni₃P precipitates separate from Ni matrix and Cu-Ni alloy forms at the interface between substrate and coating. When the fluence is up to 5×10¹⁷ions·cm^-2, oxide film forms on the surface of the Ni-P coating.6. After Co ion implantation, the hardness increased with 6% compared to un-implanted Ni-P coating. The coercivity, saturation magnetization and corrosion resistance of the Ni-P coating also improved by Co ion implantation, and their values increase with the increase of the fluence.更多还原