以天然红柱石为原料的莫来石基热障涂层设计制备与性能研究

Owing to the rigorous and complex service conditions as well as harsh requirements about high precision, high reliability and long service life of thermal barrier coatings for high-tech equipments, it is imperative to study the environmental adaptability and stability of novel thermal barrier materials under extremely high temperature. This project aims at fabrication of mullite ceramic via solid-phase reaction at elevated temperature, which will be conducted with abundant natural adalusite in Zhang county of Gansu province as the raw material. As-fabricated mullite ceramic may be adopted as a novel thermal barrier coating material with great potential and advantageous performance. Novel mullite-based thermal barrier coatings with excellent protective performance will be developed based on structure design and composition control, with which the techniques doe designing and fabricating mullite-based thermal barrier coatings will be systematically studied at depth. In the mean time, this project also aims to clarify the failure mechanism of mullite-based ceramic coatings and corresponding gradient coatings under high temperature, and study the distribution of doped elements in thermal barrier coatings as well as the influence of the dopants on the thermal conductivity, thermal expansion coefficient and high temperature stability of the coatings. By conducting the above-mentioned investigations, we hope to develop novel mullite-based thermal barrier coatings with excellent thermal stability and heat-shielding performance and establish relevant key preparatory technology, so as to establish theoretical ground and provide technical support for solving the environmental-adapting problem of thermal barrier coatings used in national security and high-tech areas.

鉴于现代高技术装备用热障涂层的服役工况越来越苛刻、条件越来越复杂，且对高精度、高可靠性及长寿命等方面的要求日益苛刻，亟需研究新型热障涂层材料在极端高温服役条件下的环境适应性和稳定性等。本项目拟利用甘肃漳县丰富的红柱石矿产资源作为原料，通过高温固相反应得到极具潜力和性能优势的新型热障涂层隔热层材料--莫来石陶瓷；通过系统深入地研究莫来石热障涂层材料体系的设计和制备技术，基于结构设计和组分控制，开发具有良好热防护功能的新型莫来石基热障涂层；研究莫来石基陶瓷涂层和过渡涂层在高温条件下的失效机理；从微观层面探讨掺杂元素在涂层体系中的分布及其对涂层热导率、热膨胀系数和高温稳定性等的影响，以期开发出具有良好热稳定性能和隔热性能的新型莫来石基热障涂层材料，并形成关键制备技术，为解决国家安全和高技术领域热障涂层材料的环境适应性问题提供理论依据和技术支撑。

利用甘肃漳县天然红柱石粉末为原料，经过高温煅烧工艺获得莫来石粉末，对制备的莫来石粉末采用喷雾造粒工艺，获得了具有良好喷涂性能的莫来石喷涂粉末，对莫来石涂层及其构筑过渡涂层制备莫来石/ZrO2-Y2O3复合涂层的热物理性能、热冲击性能和摩擦磨损等性能进行了研究。重点研究涂层的晶体结构、物相组成、微观形貌等；着重探讨涂层在高温条件下的稳定机理，以及对莫来石基涂层隔热性能和高温环境适应性能的影响；探讨了莫来石基热障涂层体系的失效机制，并开展了对莫来石基涂层体系摩擦学性能的研究。研究表明，喷涂工艺参数对涂层的沉积效率、孔隙率、结合强度、显微硬度都有重要影响；莫来石/SiO2涂层的导热系数与3YSZ涂层在1000℃时的导热系数相近，而制备的莫来石/Al2O3涂层的导热系数(1100℃)相比8YSZ涂层的导热系数略高。ZrO2的加入使得涂层的硬度和弹性模量均大于纯莫来石涂层的；梯度过渡涂层的构筑显著改善了涂层体系的热匹配性，所制备涂层的耐热冲击性能提高，同时涂层的导热率显著降低；通过对莫来石基涂层在各种环境下的摩擦性能研究，莫来石涂层在室温和高温干摩擦条件下，其磨损磨损机制是晶粒拔出和脆性断裂；而莫来石涂层在盐酸环境下摩擦时，涂层自行成的微织构形貌有利于流体润滑膜的形成，从而具有低的摩擦系数和适中的磨损率；制备的莫来石/镍-石墨复合涂层在摩擦过程中，涂层的摩擦表面均出现了再石墨化的石墨润滑膜。以上研究结果丰富了以莫来石陶瓷作为主要成分，利用热喷涂技术制备新型热障涂层材料的体系，利用莫来石为在发动机热端制备新型热防护涂层奠定了理论和试验基础，同时为莫来石涂层在各种工况环境下，作为耐磨防护涂层提供了重要的数据支撑和理论依据。