Ni3Al增强Co粘结WC基硬质合金的相图热力学及微观结构相关性研究

The price of the binder phase Co in traditional cemented carbides is high since it is a kind of strategic resources. And Co also exhibits poor acid resistance, weak oxidation tolerant, and its powder is toxic to humans. The Ni3Al and Co bonded WC cemented carbides can maintain good mechanical properties as WC-Co cemented carbides, and exhibit good oxidation and corrosion resistance at the same time, so Ni3Al+Co is ideal alternative binder phases. Choosing C-W-Co-Ni-Al multicomponent system as the target, the present investigation is devoted to: 1) based on the reliable published experimental data, construct the thermodynamic modeling of C-W-Co-Ni-Al system using a hybrid approach of the designed key experiments with CALPHAD and First-principle method; 2) design model alloys based on thermodynamic database in order to obtain the phase equilibrium data which could be used to validate and further refine the established thermodynamic modeling; 3) conduct experimental characterization of microstructure with the aid of thermodynamic simulations to study the influence of various process parameters on the phase equilibria, microstructure, morphology and mechanical properties. The presently established thermodynamic database for Ni3Al-Co-WC cemented carbides can be not only applied for the designing of alloys, but also indispensable basis to construct the thermodynamic database of multitype AlNi3+M bonded cemented carbides and carry out various structure scales of simulations.

传统硬质合金中的粘结剂Co作为战略资源，价格昂贵，耐酸性和抗氧化性能差，且其细颗粒粉末对人体有害。以具有有序L12结构的金属间化合物Ni3Al增强Co粘结的WC基硬质合金在保持传统硬质合金优良特性的同时兼具抗氧化和耐腐蚀特性，是新型粘结相的理想材料。本研究课题从C-W-Co-Ni-Al的热力学研究出发进行以下内容研究：1）基于严格的文献数据评估，并耦合关键实验、相图计算、第一性原理计算，获得该五元系的热力学模型；2）基于构筑的热力学数据库，设计关键成分合金，验证并优化所构建热力学数据库；3）基于热力学计算研究烧结工艺参数对硬质合金的成分、相组成、形貌、力学性能等的影响规律。本工作建立的C-W-Co-Ni-Al硬质合金数据库不仅可以用于WC-Co-Ni3Al硬质合金的开发，同时还为构建多类型复合粘结相M+Ni3Al硬质合金热动力学数据库以及对硬质合金显微结构进行不同层次模拟奠定了基础

硬质合金因其优异的性能，被誉为“工业的牙齿”。传统硬质合金的粘结剂Co作为战略资源，价格高且对人体有害，而具有有序L12结构的金属间化合物Ni3Al具有高强、高硬、抗氧化、耐腐蚀等优异特性，且对碳化物有良好的的润湿性，可作为Co的新型替代粘结相材料。材料的热力学信息是研究材料微结构及性能的重要基础。本工作以Al-C-Co-Ni-W五元系为研究对象开展了以下研究：1）采用四个亚点阵模型对fcc_A1/L12有序/无序转变进行了热力学描述，耦合CALPHAD方法、关键实验、第一性原理计算等构建了Al-C-Co-Ni-W的热力学描述；2）基于构建的热力学描述，设计了系列关键成分合金，校正热力学参数，最终获得了高效的Al-C-Co-Ni-W热力学描述；3）基于获得的准确的Al-C-Co-Ni-W热力学描述，设计制备了关键成分合金，分析了Ni3Al: Co粘结相配比对硬质合金显微结构组织及性能的影响规律，并从热力学角度进行了定性分析，为Ni3Al+Co复合粘结相硬质合金成分设计提供了理论指导。