低缺陷高性能陶瓷刀具的超声烧结机理及高速干切削性能研究

Ceramic cutting tools exhibit excellent cutting performance in machining difficult-to-machine materials. However, the present sintering technologies are difficult to inhibit the formation of defects such as micro-voids and micro-cracks and to refine grains in fabricating ceramic cutting tool materials, which is disadvantageous to improve the mechanical properties of ceramic cutting tools and limits the application of ceramic cutting tools. Based on this, this project puts forward a new technology – the ultrasonic sintering technology for fabricating ceramic cutting tool materials. This project will study the coupling effect mechanism of ultrasonic vibration field, sintering temperature field and sintering pressure field for revealing influence of coupling effect on ultrasonic sintering mechanism. Meanwhile, a mapping relation model between mechanical properties and the coupling effect mechanism will be built for optimizing coupling effect and then optimizing ultrasonic parameters and sintering parameters. Then effects of ultrasonic sintering parameters on the microstructure and mechanical properties of ceramic cutting tool materials will be investigated for obtaining the optimal ultrasonic sintering parameters to fabricate ceramic cutting tool materials with fewer defects and higher properties. Moreover, oxidation resistance mechanism and wear mechanism will be revealed by investigating high temperature oxidation properties and room temperature tribological properties of ultrasonic-sintered ceramic cutting tool materials, respectively. In addition, the superiority of ceramic cutting tools in machining difficult-to-machine materials will be shown through investigating the cutting performance of ultrasonic-sintered ceramic cutting tools machining typical difficult-to-machine materials under high speed dry cutting condition. These research results will lay a theoretical foundation of developing ceramic cutting tools with fewer defects and higher properties and have a practical guiding significance for machining difficult-to-machine materials efficiently.

陶瓷刀具在切削难加工材料方面展现出优异的切削性能，目前由于其烧结工艺存在难以抑制微孔洞、微裂纹等缺陷及难以细化晶粒等难题，不利于提高陶瓷刀具的力学性能，限制了陶瓷刀具的应用。本研究提出超声烧结陶瓷刀具材料的新工艺，研究超声波振动场、烧结温度场和烧结压力场的耦合作用机理，揭示耦合作用对烧结机理的影响机制，建立陶瓷刀具力学性能与耦合作用机理的映射关系模型，利用其优化耦合作用效应，进而优化超声参数和烧结参数。研究超声烧结新工艺对所制备陶瓷刀具材料的微观组织、力学性能的影响规律，研制低缺陷高性能陶瓷刀具材料。研究所制备陶瓷刀具材料高温氧化性能和摩擦磨损性能，揭示其抗氧化机制和磨损机理；研究所制备陶瓷刀具高速干切削典型难加工材料的性能，展现其切削难加工材料的优越性。本项目的研究结果将为低缺陷高性能陶瓷刀具的研制奠定理论基础，对难加工材料的高效加工具有实际指导意义。

本项目系统地研究了超声热压烧结陶瓷刀具材料的新技术，研究了超声润湿机理、超声致密机理、超声晶粒细化机理和超声耦合机理。基于此技术，与浙江晨华科技有限公司合作研制了超声热压烧结炉，并系统研究了超声变幅杆的超声特性。研究了烧结工艺参数对其微观组织和力学性能的影响，确定了相应的烧结工艺参数，研制了多种新型陶瓷刀具材料。研究了新型陶瓷刀具材料的摩擦磨损性能、氧化性能和抗热震性。在此基础上，研制出了五种新型陶瓷刀具，研究了其切削难加工材料的性能。结果表明在烧结前，对粉体施加超声，可以提高粉体的压缩率，当超声时间超过20min后，粉体的压缩率基本趋于稳定；在液相烧结中，施加超声能够提高金属相与陶瓷相间的润湿性，增大固相颗粒在液相中的驱动力，降低液相的粘度，这有利于提高材料的致密性。同时，超声空化能够提高晶格的振动频率和振动能量，从而增大形核率，阻碍晶粒的生长，起到细化晶粒的作用。在高温烧结阶段，随着烧结时间的延长，由陶瓷坯体中心到模具体外缘的径向温差逐渐减小，当保温时间为30min时，其各点的温度趋于烧结温度。随着烧结温度的升高，变幅杆的特征频率随之降低，加载冷却水可以减小特征频率的偏移。随着烧结压力的增大，变幅杆的特征频率保持不变。陶瓷刀具在与钛合金对磨时的磨损机理主要为粘着磨损、磨粒磨损和氧化磨损。随着氧化时间的延长，材料的氧化层越来越厚，由外及里出现了分层，各层形成了新的复合材料。在空冷条件下，随着热震温差的增大，材料表面的氧化层逐渐变厚。新型硼化钛基陶瓷刀具干切削高温合金GH4169后，后刀面都发生了严重的磨损，磨损机理主要为粘着磨损和沟槽磨损，刀具的使用寿命较低。新型碳氮化钛基陶瓷刀具干切削淬硬AISI H13钢后，前刀面发生了月牙洼磨损，后刀面主要发生了磨颗磨损、粘着磨损和氧化磨损，刀具的使用寿命高。这些研究结果可为其他高性能陶瓷刀具的研发提供理论和应用上的借鉴。