ZrO2溶胶/纳米颗粒协同诱导铝合金阴极等离子体电解沉积制备热防护层的组织与性能

Aiming to the urging need of thermal-protective coating on aluminum alloy worked in high temperature circumstance such as aerospace and advanced diesel engines used in vehicle and ship, cathodic plasma electrolytic deposition, CPED, has a very strong application potential for fabricating ZrO2-Y2O3 ceramic coatings which have a satisfied thermal protection role to aluminum alloy. However, there is no report about CPED of aluminum alloy at the present time, due to the difficult of cathodic plasma discharge taking place when aluminum is as the cathode. Based on the concept of combining plasma electrolytic oxidation, PEO, with co-induction role of accelerating CPED, a cast Al-Si alloy will be treated first by PEO process to get a thin electro-resistance film of alumina on the aluminum alloy, and then in-situ ZrO2 colloid and ZrO2 sol or nano particles which were added into the electrolyte will co-induce the cathodic plasma discharge taking place. As a result, the cathodic plasma electrolytic deposition rate will be improved substantially. The mechanism of the CPED process will be investigated systematically. Furthermore, the relationship between CPED process parameters and ceramic coating structure and thermal protection capability will be investigated and be put forward. In addition, the growth mechanism of nano ZrO2-Y2O3 ceramic coating and the microstructure evolution will be studied and be discovered. Hopefully, both theory and technology on fabricating thermal-protective coating with high reliability via CPED process on aluminum alloy in the condition of ZrO2 sol and nano particles inducing will be developed through the intensive study to the project. This project proposes a new method for preparing thermal-protective coating with high reliability on aluminum alloys, and establishes the theoretical foundation for preparing thermal-protective coating under the co-induction mechanism of ZrO2 sol / nano particles. This project has important scientific significance and engineering application value to expand the preparation methods of thermal-protective coating on the metals.

针对航空航天和先进车船发动机对铝合金热端部件高可靠热防护陶瓷层的迫切需求，提出采用阴极等离子体电解沉积(CPED)技术制备具有良好热防护能力的全新结构ZrO2-Y2O3纳米晶陶瓷层，但铝合金作为阴极难以引发等离子体放电。本项目基于等离子体电解氧化(PEO)与ZrO2胶体粒子/纳米颗粒协同诱导阴极等离子体放电的思想，以铸造铝-硅合金为对象，系统研究ZrO2胶体粒子和纳米颗粒作用下的阴极等离子体放电方式对ZrO2胶体粒子存在状态、稳定性及成膜过程的影响，明确其促进阴极成膜效率提高的作用机制，阐明CPED制备工艺与陶瓷层组织结构及热防护能力的关系，揭示纳米ZrO2-Y2O3陶瓷层的形成机制与组织结构演变规律。本项目提出了铝合金表面制备高可靠热防护层的新方法，奠定了ZrO2溶胶/纳米颗粒协同诱导CPED陶瓷层制备的理论基础，对拓展金属材料热防护层制备方法具有重要的科学意义和工程应用价值。

针对航空航天和先进车船发动机对铝合金热端部件高可靠热防护陶瓷层的迫切需求，本项目借助ZrO2溶胶、纳米颗粒、ZrO2溶胶/纳米颗粒协同作用、ZrO2纳米棒、碳纳米管、金属Pt颗粒诱发和促进阴极等离子体放电，进而通过阴极等离子体电解沉积（CPED）技术在铸造高硅铝合金表面制备ZrO2-Y2O3复合热防护陶瓷层。研究表明，ZrO2溶胶可以在阴极表面形成凝胶层，ZrO2溶胶、纳米颗粒、ZrO2溶胶/纳米颗粒协同作用、ZrO2纳米棒、碳纳米管、金属Pt颗粒可以促进阴极等离子体放电，提高膜层生长速率。并且一定量的ZrO2溶胶协同纳米颗粒比单一的ZrO2溶胶或纳米颗粒更容易引发阴极微等离子体放电。随着ZrO2溶胶、纳米颗粒浓度的增大，陶瓷层中Zr3Y4O12固溶体及非晶相含量有所提高；ZrO2溶胶协同纳米颗粒作用下，陶瓷层中出现新的高温固溶体相Y6ZrO11，较单一溶胶及纳米颗粒体系下形成的固溶体Zr3Y4O12的氧空位含量高，利于高温相稳定到室温。此外，ZrO2纳米棒改性的CPED陶瓷层中，形成了c-ZrO2高温相；引入碳纳米管后，t-ZrO2含量增加；引入Pt颗粒后，陶瓷层中出现高温固溶体Zr2Y4O12相。Ansys有限元分析计算表明阴极等离子放电通道内的温度可达7080℃。此外，探究了胶体粒子及纳米颗粒对膜层生长动力学的影响规律，研究了在不同CPED阶段陶瓷层显微组织及物相的演变，探求陶瓷层的生长机制。本研究初步建立了ZrO2溶胶及纳米颗粒作用下CPED陶瓷层成膜过程的物理模型。随着ZrO2溶胶、ZrO2纳米颗粒、碳纳米管浓度的增大，ZrO2纳米棒长径比的减小，隔热温度提高，且热冲击性能良好。在一定量的ZrO2溶胶协同纳米颗粒作用下，陶瓷层的生长速率及隔热温度进一步提高。引入碳纳米管、Pt颗粒后，可以有效改善陶瓷层的断裂韧性。本研究提供了一种在轻合金表面采用CPED方法制备满足优良隔热、耐热性能的热防护陶瓷层，解决了PEO方法受限于较单一的涂层材料以及文献报道的CPED方法通过热浸等方法制备绝缘阻挡膜后涂层生长速率受限等科学和技术问题，对拓展金属材料热防护层制备方法具有重要的科学意义和工程应用价值。