多尺度耦合结构高熵合金涂层的激光熔覆及强韧耐磨机理研究

Focusing on the problem of fracture failure and wear failure of the repaired key parts of mining machinery under the extreme conditions of severe impact and continuous friction, a strategy of coupling the macro-scale texture hierarchical structure with the laminated micro-nano structure is proposed, with the aim of improving the strength, the toughness and wear resistance simultaneously. Thereby, the research on structure design, preparation of alloy coating and property characterization are conducted. The main research contents include: the high-entropy alloy system with the formation ability of laminated micro-nano structure is predicted based on the thermodynamic criterion and the valence electron theory; The mechanical behavior of the coating with the designed coupling structure under friction contact and impact load is explored using the finite element method; The control of macroscopic geometry of the coating and microstructure of the high-entropy alloy is realized by the combined means of alloy compositions design and processing planning; The effects of micro-nano laminated morphologies and macro-structure on the strength, the toughness and wear resistance are investigated experimentally. Combining the analysis result of material performance with the result of the structure simulation, the multi-scale mechanism of improvement of strength, toughness and wear resistance is clarified. The results in this project should have practical value in extending the service life of the repaired parts, improving work efficiency, reducing energy consumption and cost, and have important theoretical significance for engineering application of high entropy alloy in laser cladding process.

针对矿山机械关键零部件再制造表面在剧烈冲击、持续摩擦极端工况条件下的断裂失效和磨损失效问题，以协同提高合金涂层的强度、韧性、耐磨性为目标，提出宏观尺度织构层级结构与微纳尺度硬韧堆砌结构相耦合的策略，开展基于高熵合金材料的多尺度耦合结构涂层的设计、制备和性能分析的研究。主要研究内容包括：依据热力学判据和价电子理论，预测具备硬韧堆砌微纳结构形成能力的高熵合金体系；采用有限元数值模拟方法，研究在摩擦接触、冲击载荷作用下耦合结构涂层的力学行为；以成分设计和工艺设计相结合的手段，实现对涂层宏微观结构的可控制备；实验研究微纳堆砌形态和宏观层叠结构对涂层强韧性、耐磨性的影响。结合材料性能分析和结构仿真计算的研究结果，阐明材料-结构相耦合的多尺度协同强韧、耐磨机理。本研究成果对延长修复零件的使用寿命、提高作业效率、降低能耗及成本具有实际的应用价值，对高熵合金激光熔覆工艺的工程应用具有重要的理论意义。

针对矿山机械关键零部件再制造表面在重载摩擦极端工况条件下的断裂失效和磨损失效问题，以协同提高合金涂层的强韧性、耐磨性为目标，提出宏观尺度织构层级结构与微纳尺度硬韧堆砌结构相耦合的策略，开展基于高熵合金材料的多尺度耦合结构涂层的设计、制备和性能分析的研究。主要研究成果包括：基于原子尺寸差、混合焓、混合熵和价电子浓度等热力学判据设计了能够分别实现富Ti元素颗粒相原位自生和晶间碳化物协同强化的CoCrFeNi高熵合金材料体系，分别研究了具有条幅分解诱导的纳米块状硬质相堆砌结构和连续脱溶形成的纳米球形硬质相分布结构的高熵合金涂层强化机理、热稳定性、耐磨性和影响因素。在此基础上，采用搭接和堆叠的激光熔覆工艺优化手段，实现具有微米级表面织构、梯度层级宏观尺度结构可控制备，经过量化研究明确了表面织构和梯度层级宏观结构对耐磨性和强韧性的贡献，通过摩擦学行为和力学行为的分析，阐明了材料-结构相耦合的多尺度协同强韧、耐磨机理。本研究成果对延长修复零件的使用寿命、提高作业效率、降低能耗及成本具有实际的应用价值，对高熵合金激光熔覆工艺的工程应用具有重要的理论意义。