泡沫金刚石磨粒可控制备及其磨具性能关键技术研究

Due to the difficulty of the balance between quality and efficiency and the low utilization of diamond in ultra-precision machining process for hard and brittle materials, in this project we innovatively proposed a new foamed diamond abrasive with micro/nano structures prepared by thermochemical etching. Firstly, effects of various etching reagents and dosage and reaction conditions on the diamond foaming degree will be studied. The formation mechanism and development rule of micro/nano holes in diamond particles will be proved. Secondly, the cutting mechanism and wear mechanism of diamond grains with multiple cutting edges will be analyzed. Based on this, the porosity and the pore size of diamond can be optimized. Then, diamond grinding tools will be fabricated after the special bonding material suitable for foamed diamond is selected. Finally, grinding experiments will be conducted for sapphire or BK7 glass by using foamed diamond grinding tools. The self-sharpening mechanism of tools will be explored, and their grinding performance will be evaluated. The research above can provide theoretical base and technology support for the preparation of foamed diamond grinding tools and the improvement of machining quality and machining efficiency for hard and brittle materials.

针对目前硬脆材料超精密磨削加工质量和加工效率难以兼顾、金刚石利用率低的问题，课题创新性提出采用热化学腐蚀法制备具有微纳孔结构的新型泡沫金刚石磨料。首先，研究腐蚀剂材料种类、加入量及反应条件等因素对金刚石泡沫化程度的影响，探明金刚石颗粒中微纳孔隙形成机制和规律等相关理论问题；其次，通过研究单刃细化成多刃的泡沫金刚石磨粒的切削及磨损机制，优化泡沫金刚石磨粒孔隙率和孔径；并针对泡沫结构金刚石磨粒的特点选择适配的结合剂，在对金刚石磨具的微观结构设计结合宏观组织调控的基础上，制备出泡沫金刚石磨粒磨具；最后，采用泡沫金刚石磨粒磨具对蓝宝石或BK7玻璃等硬脆材料进行磨削试验，研究磨具的自锐机制，评价分析磨具的磨削性能。通过以上研究，为制备新型泡沫金刚石磨粒磨具，提升硬脆材料的加工质量加工效率奠定关键的理论基础和技术支撑。

本研究首先利用Fe/Fe2O3对金刚石微粉进行热化学腐蚀，获得了泡沫结构的金刚石微粉，采用熔融法设计开发一种适用于泡沫金刚石的陶瓷结合剂。然后探究陶瓷结合剂对泡沫金刚石润湿性提升的机理。其次对陶瓷结合剂/金刚石复合材料的结构与性能进行表征，采用分子动力学仿真方法，建立泡沫金刚石磨削单晶硅宏观模型，通过模拟研究普通金刚石与泡沫金刚石对单晶硅的去除机理，并用普通金刚石和泡沫金刚石所制备磨具分别对单晶硅进行磨削实验，探究泡沫金刚石磨削磨损的机理，分析泡沫金刚石固结磨具代替传统研磨液减薄单晶硅的可行性。最后采用泡沫金刚石砂轮对4H-SiC晶片进行磨削试验，评价泡沫金刚石磨粒砂轮对4H-SiC的磨削加工性能。主要结论如下：. (1) 利用Fe与Fe2O3的协同差异腐蚀作用，以Fe/Fe2O3作为腐蚀剂，Fe、Fe2O3与金刚石的质量比为3:3:1，腐蚀温度为950°C，保温时间4h，腐蚀出具有泡沫结构的金刚石，孔容积达到0.141ml/g。金刚石泡沫化机理为：金刚石与Fe接触区和与Fe2O3接触区的差异腐蚀。. (2) 相较于普通金刚石，陶瓷结合剂对泡沫金刚石具有较好的润湿性。结合剂对普通金刚石膜和泡沫金刚石膜的润湿角分别为64°和29°，即减少了35°。. (3) 磨削实验表明，普通金刚石与泡沫金刚石的切削刃有很大差异，普通金刚石磨粒具有较大的单刃，以脆性切削为主，磨粒以无序破碎或从结合剂中脱离的方式实现自锐；而泡沫金刚石磨粒具有大量微纳米级的多刃，以塑性切削为主，切削深度减小，磨削热和应力得以分散，可以有效减少切削损伤，使得工件表面加工质量提高。. (4) 经粒度为W40的泡沫金刚石磨盘磨削后硅片表面残余应力值低于5MPa，硅片应力层厚度低于5nm。结果表明采用泡沫金刚石磨盘对单晶硅片进行磨削减薄后直接抛光加工，可获得高质量加工表面，泡沫金刚石固结磨盘磨削工艺能大幅降低传统工艺中酸腐、抛光的时间和成本。. (5) 常规金刚石磨粒划擦4H-SiC的去除形式主要为脆性断裂，泡沫金刚石磨粒划擦4H-SiC的去除方式是兼有脆性断裂与延性去除。泡沫金刚石砂轮在磨削4H-SiC时表现出优异性能。