M位元素固溶MAX相的高温氧化行为及润滑机理研究

Ternary laminated MAX phases have great application potential as high temperature wear-resistant materials, and solid solution modification is the ideal way to realize the integration of structure and lubricating function. In order to improve the high temperature tribological performance of MAX phases, this proposal choose metal elements as substitutions at the M sites, which have good compatibility with matrix elements of MAX phases and could oxide at high temperatures to form oxides with low shear strength. Solid solutions with both high mechanical properties and excellent high temperature lubricating performance can be further developed. The microstructures and phase composition of worn surfaces at different temperatures will be analyzed to discuss the oxidation behavior and interaction between the oxides during sliding process and temperature changing. The tribo-chemical mechanism at different temperatures can be further developed. The tribofilms under different sliding distance and their transformation will be quantitative characterized to discuss the forming and evolution of tribofilms and transfer films. The physical and chemical effects of the friction surface will be further investigated as well as the mechanism of lubrication and failure. The influencing rule and mechanism of substitution elements on high temperature self-lubricating performance and lifetime of the materials will be discussed and the new principle of structure design and control of the materials will be put forward. This proposal will reveal the influencing mechanism of substitution elements during friction process at high temperatures, and has important theoretical value and guiding significance to further improve performance, and promote the practical application of MAX phases in high-tech fields.

三元层状MAX相作为高温耐磨材料具有极大的应用潜力，固溶改性是实现其结构/润滑功能一体化的理想途径。为提高MAX相的高温摩擦学性能，本项目选择高温下能够生成具有低剪切强度的氧化物、同时与基体相具有较好相容性的金属元素作为固溶元素，探索并发展出兼具优异力学性能及高温自润滑性能的固溶体材料。通过对不同温度下材料磨损表面结构形貌特征、物相组成的分析，研究温度变化及摩擦过程中固溶体的氧化行为和氧化物间的交互作用，阐明不同温度下的摩擦化学反应机制；对不同磨程下摩擦膜厚度及转移情况进行定量表征，探讨摩擦膜及转移膜的成膜规律及演进机制，揭示摩擦表面的物理化学本质及磨损失效机理；研究固溶元素类型及固溶量对高温自润滑性能及磨损寿命的影响规律及作用机理，提出结构设计与调控的新原理。本研究能够揭示固溶元素在MAX相高温摩擦过程中的作用机制，对指导MAX相性能提升、推动其在高技术领域的应用具有重要理论意义。

固溶改性是实现三元层状MAX相结构/润滑功能一体化的理想途径。本项目选择高温下能够生成具有低剪切强度的氧化物、同时与基体相具有较好相容性的金属元素作为固溶元素，对MAX相中M位或A位原子进行晶格固溶，在基于利用晶格固溶实现MAX相的强化硬化的同时，大幅度提高材料的高温自润滑性能，以实现MAX相结构和高温自润滑性能的统一。利用热压烧结工艺，制备了不同固溶元素及固溶量的MAX相固溶体，对固溶体的制备工艺及反应机理进行了研究，进而考察了元素固溶对MAX相晶体结构及力学性能的影响。固溶体的维氏硬度及抗弯强度较传统MAX相得到了明显提升。在此基础上，对固溶体在室温至800℃宽温域下的摩擦学性能进行了系统的研究，进一步探讨了固溶元素对MAX相的高温摩擦学性能的影响机制。结果表明(Ti0.6V0.4)3AlC2及(Ti0.8Mo0.2)3AlC2固溶体在800℃下由于磨损表面发生摩擦氧化反应，生成具有低剪切的氧化物润滑膜，摩擦系数较Ti3AlC2均有显著降低。通过对不同温度下材料磨损表面结构形貌特征、物相组成的分析，系统研究了温度变化及摩擦过程中固溶体的氧化行为和氧化物间的交互作用，进而探讨了不同温度下的摩擦化学反应机制以及磨损机理。研究成果为MAX相的结构/润滑功能一体化设计提供新思路和理论依据。