基于纳米多层结构的cBN/GNCD刀具涂层增韧机制及性能研究

The project is about the research on the preparation, mechanical properties and cutting performance of cubic boron nitride (cBN) and gradient nanocrystalline diamond (GNCD) nano_multilayer structure tool coatings for difficult-to-cut materials in aviation industry. The cBN/GNCD multilayer structure tool coating is deposited by alternating reactant gas components. The toughness of the coating layer is improved by nanocrystalline and multilayer structure, so that the cutting tool coating can obtain good comprehensive mechanical properties to improve the cutting performance. The nanocrystalline cBN and diamond deposition mechanism is studied to obtain the crystalline size controllable deposition technology. The cBN/GNCD multilayer coating preparation process and its modulation deposition mechanism are studied in this project. The effects of multilayer modulated structure on the microstructure and interface characterization are investigated. The study is carried out on the effects of multilayer modulated structure on the hardness, elasticity modulus, fracture toughness, residual stress and frictional wear of the coating to discover the internal relation between nanocrystalline multilayer structure and mechanical property and the toughening mechanism of cBN/GNCD multilayer structure. The cBN/GNCD coated inserts are prepared to investigate the damage, wear and failure mechanism of the tool coating in cutting process and to establish the evolution model of cutting performance of the tool coating.

本课题面向航空难加工材料开展纳米立方氮化硼（cBN）/梯度纳米金刚石（GNCD）多层结构涂层刀具的制备及其机械性能与切削性能的应用基础研究。本课题提出改变气氛交替调制生长cBN和GNCD膜，通过纳米晶与多层结构提高涂层韧性，使刀具涂层获得良好的综合力学性能，从而提高切削性能。本课题研究cBN和NCD抑晶生长机理，形成晶粒可控的制备工艺。研究纳米cBN/GNCD多层结构涂层制备工艺及其调制生长机理。研究cBN和GNCD的调制结构对其微观结构和界面特征的影响。本课题研究纳米cBN/GNCD多层结构对涂层硬度、弹性模量、断裂韧性、残余应力以及摩擦磨损等性能的影响机理，得到多层结构与机械性能的内在联系以及cBN/GNCD多层结构的增韧机制。本课题开展纳米cBN/GNCD多层结构涂层刀具的制备，研究切削过程中涂层破损、磨损与失效机理，建立cBN/GNCD多层涂层性能演化模型。

立方氮化硼（Cubic Boron Nitride, cBN）是仅次于金刚石的第二超硬材料，耐磨性极高、摩擦系数小、导热性能和化学稳定性好，1200℃以下加工黑色金属时化学性能非常稳定，是加工高温合金和高强度钢等黑色金属理想的刀具材料。本项目通过梯度纳米金刚石(GNCD)和cBN/GNCD多层结构解决cBN涂层存在应力大和韧性低的问题。本项目分别采用微波等离子体化学气相沉积（MPCVD）和阳极层线性离子源辅助射频磁控溅射(ALLIS-RFMS)方法开展了GNCD和cBN涂层的制备，得到了高质量NCD和cBN涂层的制备工艺。通过NCD和cBN交替沉积的方法成功制备出了不同调制周期的cBN/NCD多层复合涂层，并对cBN/NCD多层复合涂层的残余应力以及机械性能进行分析，结果发现，制备的多层复合涂层和单层cBN涂层相比，残余应力明显降低，涂层断裂韧度达到了4.61MPam1/2，较单层cBN涂层提高了80%，摩擦系数0.15左右，耐磨性能和膜基结合性能良好。通过cBN/NCD多层复合涂层的裂纹扩展研究，得到了cBN/NCD多层复合涂层断裂机理：界面处纳米晶塑性导致裂纹尖端钝化和裂纹扩展到界面处发生偏转。最后开展了cBN涂层刀具的切削性能评价，cBN涂层刀具在切削过程中具有更小的切削力和更低的切削温度，通过对cBN涂层刀具后刀面磨损评价，表明cBN涂层刀具切削寿命是商用TiAlN涂层的5倍以上，通过分析涂层显微磨损特征以及涂层刀具磨损区的化学成分，得出cBN涂层刀具的主要磨损机理为磨粒磨损和扩散磨损。通过本项目的研究，将有效提高难加工材料的加工效率并降低加工成本，显著提升国产高性能刀具的技术水平，对于促进我国机械制造业和工具行业的持续快速发展具有积极的意义。