基于陶瓷颗粒表面稀土分散附着预处理下WC/钢复合材料的界面控制及其生长机制研究

As the thermal fatigue resistant materials used in the field of metallurgical and machinery industries, ceramic particles reinforced steel matrix composites are becoming a research hotspot increasingly. Control and growth of the interfaces between the particles and matrixes are the key measures to improve the service life of this kind of composites. In this project, a novel strategy is put forward to realize potential of properties of the researched steel matrix composites reinforced by WC particles, in which the surfaces of WC particles are pretreated by adhering rare earth dispersedly during the composites fabricated process. Rare earth, attached to the WC particles surfaces, will act as an important role to adjust the microstructure characteristics in the interfacial region between WC and the matrixes, such as the type, morphology and distribution of the phases and so on. Firstly, the target composites with controllable interfaces are fabricated by using a serial processes from the WC particles pretreating with rare earth above-mentioned, powder multi-pressing to vacuum sintering. The influences of fabrication parameters on the action of adhered rare earth and the formed interface microstructure are investigated through theoretical calculations and experimental methods to reveal the interface formation and control mechanism. Secondly, according to the response characteristics of the interfacial microstructures to the ambient temperature, the temperature ranges of interfacial growth are determined. Based on this temperature ranges, the interface growth mechanisms are explored through the established interface growth thermodynamics and the kinetic model. Finally, the standard of interface growth is established and the correlations between the interfacial growth and thermal fatigue properties of the composites are also explored. In summary, the key common problems about the mechanism of interface control and growth in the composites reinforced by the pretreated ceramic particles adhered with rare earth will be solved in this project. Simultaneously, the correlation mechanism between the interfacial growth and thermal fatigue properties of the composites is also finished. The interface controlling theory in ceramic particles reinforced steel matrix composites will be enriched, and a theoretical foundation for developing its application will be lay after the successful implementation of the project.

在冶金机械等行业使用的抗热疲劳耐磨材料中，陶瓷颗粒/钢复合材料成为研究热点，其寿命与界面控制及其生长密切相关。项目以WC/钢复合材料为研究体系，提出通过陶瓷颗粒表面稀土分散附着预处理方法调节界面区特征（物相、形态及分布等）从而控制材料性能的思路，首先，采用陶瓷颗粒表面稀土分散附着预处理、粉末多次压制、真空烧结等工艺，实现界面可控复合材料的制备，结合理论计算和实验，研究工艺参数对稀土存在行为和界面反应区组织的影响，揭示界面控制机制；其次，基于复合材料组织对温度的响应，确定界面生长的温度范围，研究界面生长热力学和动力学，探索界面生长机制；最后，建立界面生长程度标准，研究界面生长与热疲劳性能间的关联。项目的实施将解决陶瓷颗粒表面稀土分散附着预处理下WC/钢复合材料的界面控制、生长及其与热疲劳性能间的关联机制等共性科学问题，丰富陶瓷颗粒增强钢基复合材料的界面控制理论，并为拓宽其应用领域奠定基础。

针对在激冷激热复合工况下材料耐磨性和使用寿命不足的问题，本项目提出了利用陶瓷颗粒表面稀土分散附着预处理方法调节界面区特征（物相、形态及分布等）控制材料性能的思路，探索界面区特征与热疲劳性能间的关联机制，研究稀土元素种类、烧结温度等参数来实现WC/钢复合材料的界面控制，并通过第一性原理计算了WC、Fe基和界面相的结构性质，稀土Pm掺杂界面和稀土Nd、Y、La、Ce、Pr掺杂界面相比，热力学稳定性较差。当取代W原子时，稀土Nd掺杂的界面能最稳定，当取代Fe原子时，稀土Ce掺杂的界面能最稳定。不同稀土元素的掺杂加速了Fe元素和W元素的扩散，从而增加了复合材料的界面反应区厚度，从而增加了界面反应区反应，生成了新的Fe3W3C相。1350℃烧结不同稀土元素掺杂WC颗粒增强钢基复合材料的界面反应区宽度有所增加。未掺杂的复合材料的界面反应区宽度为14.5μm，而Y、La、Ce和Nd掺杂后，其界面反应区宽度分别增加到27.4μm、26.7μm、26.1μm和26.4μm。与稀土掺杂后，WC增强复合材料的抗压强度显著提高。掺杂稀土元素Y、Ce、La和Nd后，WC颗粒增强钢基复合材料的抗压强度分别提高到585.1MPa、410MPa、475.1MPa和659.2MPa，而复合材料的压缩率分别为13.5%、15.6%、14.5%和16.7%。解决了陶瓷颗粒表面稀土分散附着预处理下WC/钢复合材料的界面控制、生长及其与性能间的关联等共性科学问题。