WC-Ti(C,N)-Ni3Al梯度硬质合金的热、动力学及微结构控制机理研究

Due to the excellent mechanical properties, graded cemented carbides have been widely used as cutting tools. The knowledge of phase diagram thermodynamics and diffusion kinetics information for materials is the basis of quantitative description of microstructure, as well as the key of process parameter optimization and material design. However, the systematically thermodynamic and kinetic database for graded cemented carbide with Ni3Al as binder is still lacking, which results in the limitation on microstructure control and product development. Using WC-Ti(C,N)-Ni3Al multicomponent system as the target system, this project is devoted to: (1) develop the thermodynamic database through a combination of key experiments, CALPHAD approach and first-principles calculations; (2) establish the kinetic database by the modified Sutherland equations and Dictra simulation, then utilize the diffusion couple technique to acquire the reliable labyrinth factor, which represents the diminished effect of hard phase on diffusion in liquid phase; (3) investigate the effect of different alloy compositions and process parameters on the "core-rim" structure and microstructure of gradient zone in graded cemented carbide via database calculations and microstructure characterizations, and extract the mechanisms for the control of microstructure. The completion of this project is expected to lay a basis of theoretical importance for the design and development of new-type WC-Ti(C,N)-Ni3Al graded cemented carbide with independent intellectual property rights.

梯度硬质合金具有优良的力学性能，广泛用于切削刀具。掌握相图热力学和扩散动力学信息是微结构定量描述的必备条件，也是合金设计和工艺优化的关键。当前国际上Ni3Al粘结相梯度硬质合金热力学和动力学数据库的缺乏，限制其微结构控制和产品开发。本项目拟以WC-Ti(C,N)-Ni3Al多元系为研究对象，开展以下工作：（1）耦合关键实验、相图计算方法和第一性原理计算，建立该体系的热力学数据库；（2）通过修正的Sutherland方程和Dictra模拟，构建该体系液相的动力学数据库，并采用扩散偶法获取硬质相对液相扩散减弱作用的“迷宫因子”；（3）集成数据库计算及微结构实验表征，研究合金成分和工艺参数对梯度硬质合金面心立方相“芯-壳”结构和梯度层微结构的影响，并掌握其控制机理。本项目的完成可望为具有自主知识产权的新型WC-Ti(C,N)-Ni3Al梯度硬质合金设计开发奠定重要的理论基础。

Ni3Al除了良好的硬度和强度外，也具有优异的高温、抗氧化和抗腐蚀性能，代替Co作为粘结相的新型梯度硬质合金在切削刀具领域具有重大的应用前景和研究意义。掌握WC-Ti(C,N)-Ni3Al梯度硬质合金的热力学和动力学信息，进行微结构控制研究是合金设计和工艺参数优化的关键。本项目通过关键实验和理论计算的系统集成，对Al-C-N-Ni-Ti-W六元系中待完善体系开展了热力学研究，建立了WC-Ti(C,N)-Ni3Al梯度硬质合金的热力学数据库。采用修正的Sutherland方程基于元素的基本物理性质建立了液相的动力学数据库，并对表征实际扩散系数的迷宫因子进行了分析。基于相图热力学计算和扩散动力学模拟，制备出WC-Ti(C,N)-Ni3Al梯度硬质合金，并对梯度层和“芯-壳”结构的形成和控制机理进行了研究。本项目基于理论计算的新型梯度硬质合金材料体系开发方案能够为以后梯度硬质合金的设计和开发提供借鉴，并大幅缩短我国新型梯度硬质合金体系的研究周期。本项目资助期间，在Ceramics International、CALPHAD等国际知名刊物发表论文8篇，其中标注本项目资助号4篇，授权国家发明专利2项。培养硕士研究生4名。