化学气相法制备单层金刚石磨料工具新技术的基础研究

The monolayer diamond abrasive tools occupy the leading position in the grinding field with ultra-hard diamond abrasive tools. Aiming at the shortages of monolayer diamond abrasives tools fabricated by electroplating or brazing, this project presents a new technology for the preparation of monolayer diamond abrasive tools using hot filament chemical vapor deposition (HFCVD) method. , By ultrasonic vibration dispersion of diamond abrasives in photoresist solution and spin coating technique, a variety of diamond seeds is able to evenly dispersed onto the surface of SiC / WC-Co substrates with a low incidence of agglomeration. The effects of photoresist solution properties and its spin-coating process on granularity and distribution of the seeded diamonds are investigated. The ordered arrangement of diamond abrasives is also available with the aid of specially designed optical mask. Based on diamond film growth in low reactive pressure and diamond abrasives growth in high reactive pressure, this project proposes a new mechanism in the segmented growth of CVD diamond binders and single crystal diamond abrasives during the preparation process of monolayer diamond abrasive tools. Furthermore, this project studied the effects of CVD deposition parameters on the thickness and uniformity of diamond binder layers, as well as growth characteristics of single crystalline diamond grains. Besides, a new method to fabricate monolayer boron doped CVD diamond grinding tools adopting dynamic boron doping technique in CVD process is proposed. The mechanism on doping in diamonds and its effects including improvement of bonding strength, reduction of the residual stress of diamond bonded layers and promotion of growth rate of diamonds are discussed. Besides, this project reveals the effect on the boron doping technique which improves the antioxidant capacity of single crystalline CVD diamond. Characterizations of monolayer diamond abrasive tools fabricated by CVD method are conducted, mainly including the morphology, wear resistance and bonding strength of the single crystal diamond abrasives. Then the evaluation systems aiming at the grinding properties of monolayer CVD diamond abrasive tools are established. Finally, grinding experiments are conducted which testify the excellent properties of the monolayer CVD diamond abrasive tools. In conclusion, this research will lay the foundation of fabrication and application of high-performance monolayer CVD diamond grinding tools.. The new technique proposed in this project to fabricate monolayer diamond abrasive tools, can not only improve the qualities of diamond abrasives on the grinding tool surface remarkably, facilitate the crystal forms, guarantee the uniform thickness of diamond bonding layers, but also overcome the shortage of electroplated or brazed diamond abrasive tools, fulfill the fabrication of high-quality diamond abrasive tools, and acquire the diamond abrasives with strange irregular shapes less than 3%. Furthermore, the protrusion of diamond abrasives from the bonding layer reaches 70% of its height with the bonding strength at the same level as brazed abrasives. Both the abrasive quality and grinding properties are significantly enhanced compared with monolayer brazed or electroplated tools. In the meantime, we provide the effective method to fabricate monolayer diamond grinding tools with extreme fine-grained abrasives..

单层金刚石磨料工具在金刚石超硬磨料工具磨削领域占有主导地位。本项目针对单层电镀和钎焊金刚石磨料工具不足之处，提出利用热丝化学气相沉积制备单层金刚石磨料工具新技术，采用光刻胶磨料溶液超声振动旋转甩胶和光学掩模版制备模板，实现碳化硅陶瓷或硬质合金基体表面均匀有序播种金刚石磨粒晶种，研究光刻胶性能及其甩胶工艺对磨料粒度、浓度和分布均匀性的影响特性，根据低压结合剂成膜和高压单晶磨粒生长效应，揭示化学气相法金刚石涂层结合剂和单晶磨粒分阶段生长形成单层金刚石磨料工具的新机制，探讨CVD沉积工艺参数对涂层结合剂层厚度、均匀性以及金刚石磨粒单晶颗粒生长特性的影响规律，进一步采用CVD沉积过程动态掺杂技术，开发硼掺杂制备单层金刚石磨料工具CVD新工艺，分析掺杂在提高金刚石涂层结合力、减少结合剂内应力以及提高单晶磨粒生长速率等方面作用机理，揭示硼掺杂改善CVD金刚石单晶颗粒抗氧化性能的效果，在此基础上，对化学气相法制备单层金刚石磨料工具进行性能表征，研究评价单晶金刚石磨粒的晶形质量、耐磨性能以及结合强度，建立磨削性能试验评价体系并通过试验进一步显示其优异性能，为CVD单层金刚石磨料工具制备和应用奠定基础。

本项目以化学气相沉积法(Chemical Vapor Deposition, CVD)为基础，开发单层金刚石磨料工具制备新技术，实现了金刚石结合剂涂层和金刚石磨粒同步生长，揭示了金刚石磨粒的生长机理及工艺参数对磨粒形貌的影响规律，获得了CVD金刚石磨粒尺寸与出露高度的控制方法，结合硼掺杂技术提高磨粒晶形质量及生长速率，分析了磨粒的晶形特征对磨粒把持力和机械强度的影响，阐明了CVD金刚石磨料工具独特的磨削特性以及失效方式，为单层CVD金刚石磨料工具的制备和应用奠定基础。项目首先针对不同粒度金刚石籽晶，采用光刻胶旋涂法或光学掩模版法在碳化硅基体表面实现均匀布晶和有序排布，金刚石籽晶同质外延生长成为CVD金刚石磨粒，而基体上沉积异质外延金刚石涂层与同质外延金刚石颗粒形成结合剂以固结磨粒，并对CVD磨粒的形貌、纯度、截面结构、出露高度进行表征，结合剂与磨粒同步生长技术巧妙地解决了超细磨粒容易被结合剂层包埋的难题，金刚石籽晶的生长过程可以修补籽晶的形貌缺陷成为晶形统一的高品级立方-八面体单晶磨粒，进一步研究沉积工艺参数对CVD金刚石磨粒形貌、纯度、生长速率的影响，获得CVD法制备单晶、微米晶和纳米晶金刚石磨粒的工艺，通过对磨试验评价磨粒耐磨损性能，采用单颗磨粒磨削试验，分析CVD金刚石磨粒在磨损方式、材料去除形貌、力和比能等方面的特征，从微观角度揭示CVD金刚石磨粒的独特磨削特性。在此基础上，开发硼掺杂的单层CVD金刚石磨料工具，探讨掺杂工艺改善磨粒晶形质量、生长速率的作用机制，揭示掺杂对磨粒力学性能、抗氧化特性及其与涂层结合剂之间残余应力和结合强度的影响效果，结果表明掺硼磨粒的抗压强度、抗氧化性能和磨粒把持力均远高于钎焊金刚石磨粒。磨削试验结果表明CVD金刚石磨粒韧性显著提高，破碎减少，磨损方式以磨耗磨损为主，磨损后表面发生粗化，形成尖锐的金字塔结构，显著提高了磨粒锋利性，获得的超细粒度CVD金刚石磨料工具的耐磨性远高于电镀单层金刚石磨料工具，尤其适用于脆硬材料的精密磨削加工。