金刚石-立方氮化硼超硬固溶体的结构与性能调控

Synthetic diamond and cubic boron nitride (cBN) are classic examples of super-hard materials that have been widely used in industry, but both of them have limitations. Diamond, the hardest known material, can not be applied to high-speed cutting of iron group metals as a result of its poor chemical inertness. cBN does not react with ferrous materials, but its hardness is just about half of that of diamond. From the structural point of view, due to their similarity, diamond and cBN can form continuous solid solution materials which are expected to have both high hardness and high stability. This project intends to synthesize and tune the structure and properties of diamond-cBN solid solutions, and obtain the super-hard diamond-cBN solid solutions samples as well as proper preparing routines that can be practically used in industry. In the meantime, this project intends to verify the structures of the prediction models and the corresponding physical and chemical performances. By choosing proper raw materials and preprocessing methods, optimizing the pressure-temperature-time synthetic path, improving the static pressure cavity assembly and developing practical static pressure preparation technology, the applicant hope to access to different structures (including microstructures) and properties of series of large size (3 mm or above) super-hard diamond-cBN solid solutions. The applicant would characterize the structures and performances of the materials in order to establish the corresponding preparation-structure-property relationship, and obtain novel B-C-N super-hard materials with both high hardness and high heat stability. This will significantly promote the practical applications of these novel B-C-N super-hard materials.

金刚石与立方氮化硼（cBN）应用广泛，然而各有其自身的局限性：在固有性能上，金刚石为已知硬度最高的材料，但热稳定性差，不能应用于铁族金属的高速切削；cBN的热稳定性高，但其硬度仅约为金刚石的一半。二者由于结构上的高度相似性，能形成连续固溶体，可望兼具高硬度与高热稳定性,但其实际性能与精确结构尚待验证。本项目拟开展金刚石-cBN超硬固溶体材料的系统研究，实现对其结构与性能的有效调控，获得可实用化的新型超硬材料与静高压制备工艺，同时对理论上预测的结构模型与相应性能进行检验。申请人拟选用金刚石与cBN为初始材料，利用自行研制的二级大腔体静高压装置，通过高温高压下的固态反应，获得不同结构（包括微结构）与性能的大尺寸（3mm或以上）超硬块体样品，对结构、热定稳性与切削性能等进行系统表征，建立制备工艺-结构-性能的对应关系，研制兼具高硬度与高热稳定性的B-C-N材料，以获得通用型高速切削超硬材料。

金刚石与立方氮化硼（cBN）作为超硬材料应用广泛，然而各有相对局限性：在固有性能上，金刚石为已知硬度最高的材料，但热稳定性差，不能应用于铁族金属的高速切削加工；cBN的热稳定性高，但其硬度仅约为金刚石的一半。二者由于结构上的高度相似性，能形成连续固溶体，可望兼具高硬度与高热稳定性,但其实际性能与精确结构尚待验证。本项目对金刚石-cBN超硬固溶体材料进行了系统研究，对其结构与性能已实现有效调控，获得可实用化的新型超硬材料与静高压制备工艺，同时也对理论上预测的结构模型与相应性能进行验证。申请人选用不同粒度的金刚石与cBN 为初始材料，利用自行研制的二级大腔体静高压装置，通过高温高压下的固态反应，获得了不同结构（包括微结构）与性能的大尺寸（3 mm或以上）超硬块体样品，并对块体样品的结构、热定稳性与切削性能等进行了系统表征，建立起制备工艺-结构-性能的对应关系，研制兼具高硬度与高热稳定性的B-C-N材料，获得了通用型高速切削超硬材料。项目实施期间发表了相关论文26篇。其中部分成果（Diamond-cBN Alloy）于2015年09月08日发表在最新一期的《Applied Physics Letters》杂志上（http://dx.doi.org/10.1063/1.4929728）（详细链接）。并被美国物理联合会（AIP）以新闻稿“Half diamond, half cubic nitride, all cutting business”重点介绍，随后被多家国际著名科学网站如Sciencedaily (Top news),EurekAlert(AAA旗下)，Physics News,ChemEurope,Asian Scientist,福布斯杂志等转载报道40余次。