TiAlCrTaWN高熵涂层的高温结构稳定性、蠕变行为和抗氧化性研究

To meet the increasingly sophisticated requirements of advanced cutting techniques, the project intends to obtain TiAlCrTaWN high-entropy coatings with excellent high-temperature structural and mechanical stability through the synergistic addition of Cr, Ta, and W. First of all, the first-principles calculations will be used to predict the structural stability, elasticity and mechanical properties of multicomponent nitrides, and provide theoretical guidance for the subsequent design and preparation of coatings. Secondly, the structure and toughness of multi-component coatings in the as-deposited state will be studied to verify the reliability of the theoretical calculation. Using the high-temperature nanoindentation technology, we will further investigate the in-situ creep behavior of coatings at elevated temperature and reveal their creep mechanism. Finally, the structure evolution, age hardening and oxidation behavior of coatings at high temperature will be studied, and the mechanism of the alloying effect of Cr, Ta, and W on the thermal stability and oxidation resistance will be elucidated to obtain multi-component coatings with the excellent comprehensive performance. This work will provide a highly efficient and feasible method for the design and performance optimization of multi-component hard coatings. And high-performance TiAlCrTaWN coatings prepared can significantly enhance the cutting capacity of tools and service the field of high-speed cutting.

为适应先进切削技术日趋复杂的使用要求，本项目拟通过Cr、Ta和W的协同添加来获得具有优异高温结构和力学性能稳定性的TiAlCrTaWN高熵涂层。首先采用第一性原理计算预测多组元氮化物的结构稳定性和弹性、力学性质，为后续涂层的设计和制备提供理论指导。然后，研究所制备的多组元TiAlCrTaWN涂层常温下的结构和韧性，验证理论计算的可靠性。并借助高温纳米压痕技术，进一步研究涂层原位高温下的蠕变行为，揭示其蠕变机制。最后，研究涂层在高温下的结构演变、时效硬化及氧化行为，阐明Cr、Ta和W的合金化添加对涂层热稳定性和抗氧化性的作用机理，获得具有优异综合性能的多组元涂层。本项目的完成将为多组元硬质涂层的设计和性能优化提供一种高效可行的方法，制备的高性能TiAlCrTaWN高熵涂层可显著加强刀具的切削性能，应用于现代高速切削领域。

传统涂层刀具已逐渐难以满足日趋严苛复杂的切削应用，刀具表面涂层的性能成为制约切削加工效率提升的主要因素。基于此，本项目从材料成分设计出发，引入高熵合金理念拟开发具有优异力学性能、热稳定性和抗氧化性的多组元氮化物涂层。首先研究TiAlCrTaWN多组元涂层结构、韧性和抗蠕变性能；然后研究TiAlCrTaWN涂层在高温下的结构演变和力学响应；最后研究合金元素Cr、Ta和W对TiAlN高温氧化行为的作用机制。相比于TiAlN和单合金元素添加的涂层，TiAlCrTaWN涂层具有更好的韧性及蠕变抗性。此外，高熵效应使TiAlCrTaWN涂层具有更加优异的结构稳定性同时表现出时效硬化特性，900°C退火后硬度升高至35GPa，且1100°C时硬度依然保持在32GPa。氧化过程中，Cr促进初期致密氧化铝层的形成、Ta延缓中期氧通过氧化钛层向内扩散的速率，W形成纳米氧化物提升氧化物与氮化物的结合，三者协同提升了TiAlN涂层的抗氧化性。本项目的完成为高性能氮化物涂层的设计提供了切实可行的策略和坚实的实验基础，开发的TiAlCrTaWN高熵氮化物涂层有望应用于难加工材料的高速切削。