Fe-Co-Cu金刚石锯片制备及微波烧结机理研究

Metal binder of Fe-Co-Cu ternary system is an ideal substrate to realize the diamond saw blade with low cobalt content. However, it is difficult to avoid the high sintering temperature and the inadequate element diffusion for the traditional hot pressing sintering method by adopting the elementary substance powder as the metal matrix material, which results in the intensity heat loss of diamond and the composition segregation of sintered product. Therefore, microwave as a unique heating way is suggested in the present proposal. We attempt to obtain the dynamic change of material electromagnetic properties at high temperature by the investigation of heating rate curve in the microwave field. In order to confirm some critical microarchitectural information such as the existing state of elements in the sintered compact, the phase of interfacial transition layer and the bond strength of diamond, we will adjust the process parameters such as sintering temperature and sintering time, and then utilize some indispensable measure methods including the high temperature X-ray diffraction, the micro area energy spectrum of scanning electron microscopy, the nano scratch test and the high temperature friction and wear test, etc. Through the above research, we aim to obtain the correlative law between parameters in the process of microwave hot pressing sintering, to explore the microstructure evolution law under different process conditions, to clarify the multicomponent strengthening migration and transfer law in the microwave field, to reveal the synergistic strengthen mechanism of the reaction process between multicomponents, and finally to form the novel process and mechanism of microwave hot pressing sintering. The implementation of this project provides a novel sintering method at low temperature for cobalt-based diamond saw blade, and the formed generic technology and sintering mechanism can provide theoretical reference to research and develope the diamond tools of metal bond matrix with low cobalt content.

Fe-Co-Cu三元金属结合剂是实现金刚石锯片低钴化的理想基体，然而以单质粉末为原料，采用常规热压烧结存在烧结温度高、元素扩散不充分等问题，导致金刚石强度热损失和组织成分偏析。针对该问题，本项目基于微波独特的加热方式,通过研究物料在微波场中的升温速率曲线，获取烧结过程中的高温动态电磁特性变化规律；通过调控烧结温度和时间等工艺参数，利用高温X射线衍射、扫描电镜微区能谱、纳米划痕、高温摩擦磨损等测试手段，分析烧结体中元素赋存分布状态、界面过渡层物相和金刚石结合强度等关键微结构信息，进而获得微波热压烧结工艺参数关联规律，探索不同工艺条件下的微结构演变规律，明确微波场作用下的多组元强化迁移和传递机制，揭示多组元协同组织强化机理, 最后获得微波热压烧结新工艺和新机制。本项目的开展将为铁钴基金刚石锯片提供一种新颖的低温烧结方法，形成的共性技术和烧结机理，可为研发低钴系金属结合剂金刚石工具提供理论借鉴。

利用微波加热具有能量原位转化、烧结温度低、烧结时间短等优点，开发微波热压烧结技术制备低钴型FeCoCu结合剂金刚石锯片刀头。研究金属结合剂配方颗粒在微波场中的强化烧结机制，以及微波烧结工艺参数对样品微观结构和力学性能的影响规律，形成微波热压烧结低钴型金刚石锯片新工艺，为难烧结金属基金刚石制品微波低温烧结提供理论依据。研究结果如下：(1) 测定了配方中金属粉体的高温动态介电常数和升温特性，结果表明，低钴型金刚石锯片金属结合剂原料在微波场中表现出良好的吸波特性，其介电损耗和升温速率随着烧结温度升高而增大，在850℃后趋于稳定，从理论层面验证了微波热压烧结是制备低钴型金刚石锯片的可行方法。（2）针对微波热压烧结低钴/无钴型FeCoCu金刚石锯片进行了系统研究，探索烧结配方组成、烧结温度、烧结压力、保温时间等对样品性能的影响，并对样品的致密度、硬度、抗弯强度、冲击韧性等力学性能进行了测试，优化了烧结工艺参数。（3）确定了“低Co中Fe高Cu”、“无钴高Fe中Cu”、“无钴高Fe中Cu含W”三类金属基金刚石锯片的结合剂优选配方，通过SEM、EDS、EPMA等现代分析方法，对比研究了三类配方在微波热压和常规热压烧结下得到样品的微观形貌、组织元素分布等微结构信息，明晰了烧结过程中微波对元素的强化迁移行为和冶金反应机制，进而通过建立样品微结构和力学性能间的关系，优化出相应配方的最佳微波热压烧结制度。结果表明，在相同的烧结制度下，微波烧结样品的致密度、硬度、把持系数、冲击韧性等力学指标均优于常规烧结样品，微波热压烧结新方法将难烧结配方的温度降低至1000℃以下，有效避免了金刚石磨料因高温烧结导致的热损伤。（4）金属粉体在微波场中通过材料自身的介电损耗、涡流加热等机制实现原子层面的能量原位转换，增加金属原子的活性，通过微区熔池搅拌、液相元素重排等效应，促进金属元素的扩散和合金化反应。（5）微波内部加热在样品产生的由内到外温度梯度，极大促进了组织收缩时气体逸出，有利于减少烧结组织的微观孔缺陷，可显著提高样品的力学性能。在保证同等力学性能前提下，微波烧结制度允许更高的升温速率和更短的烧结周期来实现致密化烧结。通过项目实施，共发表论文11篇，已被SCI、EI收录9篇；申请专利6件，授权2件，公开4件；参与组织国内外学术会议11次，开展国际合作交流互访5次；培养博士研究生1人，硕士研究生2人。