梯度结构与超细晶粒协同作用Ti(C,N)基金属陶瓷的制备及形成机理研究

To solve the irreconcilable conflict between high strength and wear resistance of Ti(C,N)-based cermets , and meet the high performance requirements of tool materials in the difficult processing fields of high-end equipment, a design concept of ultrafine grains and gradient structure synergistic improved material properties and a method of preparation in a complete negative pressure sintering process are proposed: preparing the ultrafine Ti(C,N)-based cermets by in-situ carbothermal reduction nitridation in the heating stage, and then preparing the graded Ti(C,N)-based cermets enrich in hard phase of the surface via a two-step composite nitriding treatment technique in the cooling stage. The formation and strengthening mechanism of the ultrafine Ti(C,N) grains by in-situ reaction will be studied. The formation mechanism and the kinetic equation of the gradient harden layer will be studied. By doing so, it is hoped that the relationship among material composition, negative pressure treatment process parameters, microstructure, interface structure, composition distribution and mechanical properties can be established, and the controllable preparation principle of high performance gradient ultra-fine cermets can be revealed. We hope that the proposal will provide an important theoretical basis and scientific method for the development of high-performance tool materials.

为解决金属陶瓷的高强韧性和耐磨性难以同时兼顾的问题，满足高尖端设备难加工领域对刀具材料高性能的需求，提出了超细晶粒与梯度结构协同改善材料性能的设计理念。在一个完整的负压烧结程序中，采用升温阶段的原位碳热还原氮化处理技术制备超细Ti(C,N)基金属陶瓷；并结合降温阶段的两步复合氮化处理技术，在其表面形成较厚的梯度结构硬质相层。研究超细Ti(C,N)晶粒原位形成机理及其强韧化机制；研究梯度结构硬质相层形成机理；并建立梯度层形成动力学数学模型。在实验基础上，建立材料成分、负压处理工艺、显微组织形貌、界面结构特征、元素梯度分布与力学性能之间的多重映射关系，揭示高性能梯度结构超细金属陶瓷的可控制备原理，为高性能工磨具材料的研制提供理论基础和科学方法。

为解决金属陶瓷的高强韧性和耐磨性难以同时兼顾的问题，满足高尖端设备难加工领域对刀具材料高性能的需求，提出了超细晶粒与梯度结构协同改善材料性能的设计理念，研究了梯度结构超细Ti(C,N)基金属陶瓷的形成机理。研究结果表明；原位制备技术可以成功制备超细Ti(C,N)基金属陶瓷，其硬质相和粘结相呈共格关系，提高了材料的强韧性，并揭示了硬质相晶粒的生长方式遵循立方定律并受扩散控制；采用负压氮化处理技术可成功制备表面富硬质相梯度结构Ti(C,N)基金属陶瓷，得到了氮化处理工艺、显微组织、成分分布和力学性能的多重映射关系，阐明了表面富硬质相梯度层的形成机理，并构建了金属陶瓷表层富硬质相梯度层的形成动力学模型。本项目的研究掌握了高性能梯度结构超细金属陶瓷的可控制备原理，为制备不同特点高性能工磨具材奠定基础。