【作者】 潘秉锁；

【导师】 杨凯华；

【作者基本信息】 中国地质大学 ， 地质工程， 2003， 博士

【摘要】 近数十年来金刚石工具的制造工艺有了很大的发展，应用领域也在不断扩大，已在地质勘探、石油开采、建筑材料加工、宝玉石加工、医疗保健、塑料制品模具制造等领域获得了广泛的应用。在众多的金刚石工具制造方法中，电镀法具有独特的优点，在探索和研究不用高温制造金刚石工具的方法方面是最有前途的方向之一。作为一种重要的电镀金刚石工具，电镀金刚石钻头已经过三十年的发展，其制造水平有了很大的提高，但还存在着许多问题，如金刚石钻头生产周期长、质量不甚稳定、适应范围窄等。通过从配方到工艺的研究获得快速电镀金刚石钻头的研究成果，提高钻头的生产效率和质量，以满足不断扩大的市场需求，是一件迫切而有意义的事情。电镀金刚石钻头一般采用金属镍或镍钴合金作为胎体材料。虽然在表面工程中镀镍已进行了大量的基础研究和应用研究，但金刚石钻头所要求的镀液和镀层的性能与这些表面工程领域研究的镀液和镀层的性能有着很大的差别。因此，在电镀金刚石钻头制造工艺研究中，需要更多有针对性的研究。稀土元素独特的 4f层电子结构使得稀土金属或合金具有独特的功能，稀土材料是材料科学领域中的一个热门研究课题。在电镀方面，稀土已在镀铬、镀锡等镀种中获得了成功的工业应用，但到目前为止稀土在镀镍中的应用报道还很少，而有关稀土对镀层机械性能影响及其在电镀金刚石工具方面的应用的报道还没有。本文的目的是借鉴稀土在电镀中的成功应用经验，把稀土引入电镀金刚石钻头的制造中，通过试验和理论分析获得电镀金刚石钻头的最佳电镀工艺条件，以解决当前电镀金刚石钻头中存在的问题，达到电镀金刚石钻头的快速、优质生产。通过分析，选择稀土添加量、镀液硫酸钴含量、温度、电流密度、镀液pH为影响镀层和镀液性能的因素，每个因素各研究了四个水平，试验采用正交设计方法安排。在电镀中，金属镀层的性能是由镀液组成及电镀工艺参数决定的。作为金刚石钻头的胎体材料，镀层所应具备的性能与表面工程中要求的镀层性能既有相同的一面，又有其特殊的一面，从而对镀液性能的要求也就不同。分析认为，用于制造金刚石钻头的镀液要具有良好的分散能力，深镀能力的要求则可以稍低，而在镀液稳定性、电流效率、腐蚀性等方面的要求则是与表面工程一致的。在镀液性能方面，本文主要考虑了镀液分散能力、深镀能力、电流效率等指标。分散能力采用远近阴极法测定。在试验范围内，镀镍液的分散能力随稀土添加量的增加而升高。与基本镀液（分散能力为-7.7%）相比，添加稀土的镀镍液的分散能力有很大的改善，可克服普通镀镍液分散能力差的不足。温度对镀镍液的分散能力也有较大的影响。随着镀液温度的升高，镀液的分散能力也逐渐提高。这可能与温度升高使镀液的导电能力提高有关。深镀能力采用内孔法测定。添加稀土后，镀液深镀能力下降。镀液的pH值对深镀能力有很大的影响，pH值从3升高到4.5时，深镀能力提高了31.6%。当pH 值低于4.0时，pH的影响尤其明显。硫酸钴的加入对深镀能力也有一定的提高作用，而温度对镀液的深镀能力有一定的降低作用。这些因素对镀镍液深镀能力和分<WP=6>散能力的影响可以从镍的沉积机理——金属羟合络离子假说来解释。镀液的电流效率通过比较各空白镀液中氢析出的极化曲线评定。镀液底液中氢在玻碳电极上析出的极化曲线表明，随着底液中稀土浓度的升高，氢的析出电流降低。因此，稀土元素的加入有抑制析氢反应的作用，从而可提高镀液的电流效率。本文认为，稀土对镀液性能的影响可能与电沉积过程中阴极附近pH值升高而导致的稀土阳离子水解有关。稀土阳离子的水解对阴极的局部pH起到了一定的缓冲作用，减少了镍的水解；稀土阳离子的水解产物在阴极的吸附则有一定的增加阴极极化作用。镀液的循环伏安曲线表明，稀土的加入没有改变镍电结晶时的极化类型，即本体沉积时阴极过程由电荷传递步骤控制，异相沉积时由成核步骤控制。初始电位为-0. 5V、阶跃电位在-0.85～-1.05V vs. S.C.E之间的单电位阶跃实验结果显示，稀土的加入也没有改变镍电结晶的成核形式和生长方式，电结晶仍按瞬时成核和三维生长方式进行，但稀土可以促进镀层在垂直于基体方向上的生长速度。镀层机械性能的优劣直接关系到镀层的实用价值与应用范围，因此在镀层的开发过程中需要对它们进行测试，以确定合理的工艺条件。由于工作条件和作用不同，作为钻头胎体材料的镀层应具备的性能也与普通镀层不同。本文通过分析，选择镀层硬度、耐磨性、镀层与基体的结合强度、内应力和孔隙率等性能作为研究指标，也对镀层的物相、成分、表面形貌及镀层对金刚石的包镶进行了研究。镀层的硬度采用显微压入硬度法测定。结果表明，随着硫酸钴加量的增加，镀层的硬度有很大的提高，但当硫酸钴添加量超过10g/L时，镀层硬度基本上维持不变。硬度增大的原因是加入的钴离子能和镍离子在阴极共沉积，形成了镍钴固溶体。从镀层中的钴含量随镀液中硫酸钴含量的变化情况可以看出，在研究的镀液体系中当镀层中钴含量低于17%左右时，镀层硬度随钴含量的增加而快速升高；钴含量再增加时，硬度基本不变。镀层硬度随镀液操作温度的变?更多还原

【Abstract】 There have been great improvements in the manufacture of diamond tool in past several decades. Its applied range has been expanded continuously and extensive applications to geological exploration, petroleum extraction, machining of building materials, processing of gem, medical care and manufacturing of plastic products obtained. Among the methods for manufacturing of diamond tools, electroplating method has unique merits and is one of the most promising direction in the research of manufacturing diamond tools disusing of high temperature. As an important kind of electroplated diamond tool, electroplated diamond bit has been developed for thirty years and its manufacturing technique has been highly improved. However, some problems still exist, such as long production cycle, quality instability, narrow applied range. So it is impending and significant to realize high-speed production of electroplated diamond bit to increase production rate and quality in order to meet the expanding market demand. The main content of electroplated diamond bit research is research of electroplating matrix material. Electroplated diamond bit usually adopts nickel or nickel alloy as matrix material. Although nickel electroplating has been studied extensively in surface engineering, in electroplated diamond bit research more directing researches are needed owing to the different requirements of performances of plating bath and deposit between in diamond bit electroplating and in surface engineering. Rare earth material is a hot direction in material science due to the unique 4f electronic shell structure of rare earth elements, which results in the special properties of rare earth metal and rare earth alloy. In electroplating, rare earth has been industrially applied to chromium electroplating and tin electroplating. But there are few applied reports on rare earth in nickel electroplating so far and no report on effect of rare earth on mechanical property of deposit and performance of electroplated diamond tool is found. Drawing lessons from successful application of rare earth to electroplating, this paper is to introduce rare earth into the manufacture of electroplated diamond bit to obtain optimum electroplating technique of electroplated diamond bit through experiments and theoretical analysis, realizing the high speed and high quality production of electroplated diamond bit. Through analysis, concentration of rare earth, concentration of cobalt sulfate, bath temperature, cathodic current density and bath pH were chosen as elements affecting the performance of deposit and plating bath. For every element, four levels were studied. Experiments were scheduled by orthogonal design method.In electroplating, the performance of deposit is dependent on bath composition and electroplating operational parameters. As matrix material of diamond bit, deposit should have some performances same as those required in surface engineering, at the same time other special performances are required. So different bath performances are required. Bath for electroplating diamond bit needs good throwing power, but its covering power can be a little lower. Among<WP=9>bath performances, throwing power, covering power and current efficiency were considered in this paper. Throwing power was measured by far-cathode near-cathode method. In experimental scope, bath throwing power increases with the increasing concentration of rare earth. The throwing power of conventional nickel bath was -7.7%. Compared to that of conventional nickel bath, the throwing power of bath with rare earth had been enhanced obviously. So addition of rare earth can overcome the shortcoming of bad throwing power of conventional bath. Bath temperature also had clear effect on throwing power. With the increase of bath temperature, the throwing power increases little by little. This may be related to the increase of bath conductivity resulting from high temperature. Bath covering power was measured by inner hole method. With the presence of rare earth, bath’s covering power decreased更多还原