Surface Modification of Fine Diamond Grains by High-Frequency Magnetron Sputtering

在进行数控镜面磨削的情况下，自由成型模具的精加工应采用细晶、耐磨的球形金刚石砂轮。用镍离子电沉积金刚石颗粒的电镀金刚石工具，与传统的粉末冶金方法生产的砂轮相比，具有更好的耐磨性。然而，刀具的形状精度和磨削性能受到重视，因此在刀具本体上只电沉积了一层金刚石颗粒。因此，刀体上单层金刚石颗粒的切削刃保持锋利的刀具寿命是有限的。使用电铸工具可以提高电镀工具的使用寿命，在电铸工具中，厚实堆积的金刚石颗粒与镍离子一起电沉积。然而，传统的共沉淀法生产厚涂层需要很长的时间，因为必须重复进行一系列过程，包括剧烈搅拌、悬浮颗粒的沉积和电沉积。为了克服传统工艺的不足，本研究开发了一种低速搅拌技术来制备高颗粒密度的厚壁复合涂层。高速电铸是通过低速搅拌沉淀颗粒来提高电导率。此外，通过在颗粒表面覆盖氧化物涂层，增加了金刚石颗粒对粘结材料的夹持强度。

A spherical diamond wheel with fine grains and superior wear resistance should be adopted for the finishing process of free-formed dies and molds in cases where numerically controlled mirror grinding is performed. An electroplated diamond tool in which diamond grains are electrodeposited with nickel ions exhibits superior wear resistance compared with conventional wheels produced by the power metallurgy process. However importance is given to shape accuracy and grinding performance of the tool, thus only a single layer of diamond grains is electrodeposited on the tool body. Hence, the tool life in which the cutting edges of the single-layered diamond grains on the tool body remain sharp is limited. The tool life of the electroplated tool can be increased by using an electroformed tool in which thickly stacked diamond grains are electrodeposited with nickel ions. However, the conventional sediment codeposition technique requires an extremely long time for the production of thick coatings, since a series of processes consisting of vigorous agitation, sedimentation of floating grains and electrodeposition must be conducted repeatedly. In this study, a low-speed agitation technique is newly developed to produce thick composite coatings with high grain density to overcome the disadvantages of conventional techniques. High-speed electroforming is conducted by agitating sedimented grain particles at a low speed to increase the electric conductivity. In addition, the gripping strength of diamond grains to the bond material is increased by covering grain surfaces with oxide coatings.