NiCo基宽温域润滑涂层的高温自适应机理及摩擦磨损性能研究

The lubricating coating with a long service life and high reliability used in a wide temperature range is a research focus in tribolocial properties of advanced materials, and the involved high temperature lubricating is a difficult technical problem facing in the development of high tech equipment. The self-adaptive lubricating NiCo-based coatings with excellent tribological properties in a temperature range from room temperature to 1000 ºC are prepared by HVOF technology in this application. Their oxidation thermodynamics, oxidation kinetics and tribological properties as well as corresponding mechanisms are systematically studied by static high temperature oxidation test and high temperature friction and wear test to elucidate the formation-evolution process and mechanism of new phases in coatings at 800~1000 ºC, and to reveal the intrinsic response relationship between the composition and crystal structure of new solid lubricants composed by oxides and inorganic oxysalt and high temperature lubricating behavior. The adaptive formation mechanism of high temperature solid lubricants in the coatings at high temperatures is investigated, and the high temperature tribological mechanism and the physical and chemical phenomenal in the friction process are emphatically studied. The influences of environmental conditions on the surface chemical composition and microstructure of materials as well as the friction chemical reactions on the generation of lubricating film are analyzed by the modern analysis methods. After the above investigations, the self-adaptive lubricating mechanism of NiCo-based self-lubricating coatings at high temperatures and its positive effect on the tribological properties are revealed and clarified, finally establishing the scientific theories and design principles of self-lubricating coatings.

长寿命、高可靠的宽温域自润滑涂层是新材料摩擦学研究的热点，而涉及的高温润滑问题又是高技术装备发展面临的技术难题。项目采用HVOF工艺制备在1000℃范围内具有优异摩擦学性能的NiCo基自适应润滑涂层；将涂层的“氧化热力学-动力学-摩擦学”原理相结合，通过“静态高温”和“高温摩擦耦合”试验，系统阐明高温下（800℃~1000℃）涂层中新物相的“生成—演变”过程和机理，揭示氧化物、无机含氧酸盐等新型固体润滑剂的组分、晶体结构与高温润滑本质之间的内在响应关系；研究涂层在高温下自适应形成高温固体润滑剂的具体机制，尤其是涂层的高温摩擦学响应机理和摩擦过程中的摩擦物理化学现象；借助现代分析手段，研究环境条件对材料表面化学组成、微观结构以及摩擦化学效应对润滑膜形成的影响机制。通过研究，揭示和阐述NiCo基宽温域自润滑涂层在高温下自适应的润滑机理和其在摩擦过程中所起的积极作用，最终建立自润滑涂层的科学理论

采用HVOF工艺制备1000℃范围内具有优异摩擦学性能的NiCo基自适应润滑涂层；将 “热力学-动力学-摩擦学”原理相结合，通过“静态高温”和“高温摩擦耦合”试验，阐明高温下涂层中新物相的“生成-演变”过程和机理，揭示氧化物、无机含氧酸盐等新型固体润滑剂的组分、晶体结构与高温润滑本质之间的内在响应关系；重点研究了涂层在高温下自适应形成高温固体润滑剂的具体机制，包括涂层高温摩擦学响应机理和摩擦中的物理化学现象。. 项目具体开展了NiCoCrAlYTa涂层在1000 ℃大气环境中的抗氧化性，从金属氧化热动力学入手，揭示涂层表面氧化物钝化层的生长机制，并研究不同氧化诱导时间对涂层微观结构、力学性能、室温及宽温域内的摩擦学性能的影响。通过复配掺杂及组分优化制备了NiCoCrAlYTa /Ag/Mo复合润滑涂层，揭示了高温条件下涂层内部组织和物相的变化过程，尤其是β-Ag2MoO4润滑剂的原位生成机制以及该物质在摩擦过程中的作用机理，即只有在600 ℃以上时，复合涂层表面才逐渐开始有润滑相β-Ag2MoO4生成；但600 ℃摩擦起主导润滑作用的仍是软金属Ag的外扩散及其在摩擦界面的铺展；当摩擦温度为800 ℃时，原位生成的类层状β-Ag2MoO4可以在磨痕表面形成连续的润滑膜，表现出最为优异的润滑作用；同时，适量的Al2O3硬质相小颗粒的生成可以在摩擦过程中起到良好的承载和滚轴作用，从而降低了复合涂层的磨损率；当摩擦环境温度为1000 ℃时，混合氧化物含量急剧增多，在摩擦过程中形成磨粒磨损，导致β-Ag2MoO4在磨痕表面不能形成连续润滑膜。同时揭示了 . NiCoCrAlYTa/10Ag/5Mo自适应润滑复合涂层在Na2SO4-NaCl，Na2SO4-NaCl-V2O5两种熔盐介质下的抗热腐蚀性能及其对相应的腐蚀/磨损交互作用机制，表明熔盐介质加速复合涂层的氧化，含V熔盐的腐蚀作用更为剧烈，其中涂层基质相和掺杂相交界处的腐蚀更显著，腐蚀产物的过度生成导致涂层表面局部区域微裂纹形成；高温条件下涂层内部元素的互扩散以及晶粒的充分生长导致其力学性能有所提升，并且热腐蚀后大量硬质氧化物的生成改善了涂层的耐磨损性能。