热压滤溶胶-凝胶制备新型高温可磨耗封严涂层的结构与特性研究

The high hardness which was prone to abrading the engine blades and the block spallation which may affect the operation of engines were the key scientific problems for thermal spray coatings. In this project, high-temperature abradable seal coatings were prepared by a new process which was called thermal pressure filtration sol-gel method. Novel ceramic matrix abradable seal coatings with much more uniform structures and many micropores were prepared by this method. The hardness and cutting property of the coating were improved by the non-melting sintering structure and much more uniform micropore structure in the coating, which made a balance of the abradable property and erosion wear resistance for the coating. The large amount of micropores and microcracks in the coating could also release the thermal stresses generated during thermal cycling and made the coating have a good thermal shock resistance. The coating structures were further optimized by means of doping rare earth oxides and dispersing nano Al2O3 praticles. Their influence on abradable property, erosion wear resistance and thermal shock resistance were investigated and the relevant mechanisms were discussed. This research provides new theories and new technological approach for the development of novel high-temperature abradable seal coatings with excellent abradable property, erosion wear resistance and thermal shock resistance.

本项目针对热喷涂陶瓷基高温可磨耗封严涂层硬度较高容易造成叶片磨损以及容易产生大块摩擦剥落影响发动机运转这一关键科学问题，提出采用热压滤溶胶-凝胶法制备陶瓷基高温可磨耗封严涂层新工艺。利用溶胶-凝胶法独特的制备工艺，制备高度均匀且具有大量微孔结构的新型陶瓷基高温可磨耗封严涂层。通过涂层的非熔融性烧结结构和高度均匀微孔结构来改善涂层的硬度及可切削性，使涂层的可磨耗性能与抗冲蚀性能达到最佳平衡；利用涂层中大量存在的微孔和微裂纹结构松弛冷热循环中产生的热应力，使涂层具有优异的抗热震性能。并通过稀土氧化物掺杂或纳米Al2O3弥散进一步优化涂层结构，研究其对涂层可磨耗、抗冲蚀以及抗热震性能的影响及机制。为研究发展具有更优可磨耗、抗冲蚀以及抗热震性能的新型陶瓷基高温可磨耗封严涂层提供新的理论和新的技术途径。

本项目自行设计研制了溶胶-凝胶热压滤装置，在此基础上采用热压滤溶胶-凝胶技术制备了（ZrO2+h-BN+聚酯）、掺杂稀土氧化物（Y2O3）和弥散纳米Al2O3三种新型陶瓷基高温可磨耗封严涂层。获得的主要研究结果如下：（1）采用热压滤溶胶-凝胶技术制备了（ZrO2+h-BN+聚酯）三相陶瓷基高温可磨耗封严涂层，研究了热压温度、热压压力和粉胶比对涂层组织结构和特性的影响。研究结果发现：热压滤工艺的最佳热压温度处理制度为室温~200℃，升温速率1℃/min，165℃保温30min；200℃~400℃，升温速率2℃/min，400℃保温1h；5℃/min升温至1150℃，保温1h。当热压压力为20MPa、粉胶比为9:1时涂层的性能最佳，具有适中的硬度、良好的抗冲蚀性能和抗热震性能，涂层在1100℃的抗热震寿命为160次。（2）研究了掺杂稀土氧化物Y2O3新型四相高温可磨耗封严涂层的组织结构与特性。研究发现：当Y2O3掺杂含量在15mol%时，涂层具有最佳的表面形态和性能，涂层的硬度与三相可磨耗封严涂层接近，涂层主要由四方相Zr0.92Y0.08O1.96和ZrO2组成，涂层的抗热震性能较热压滤溶胶-凝胶三相可磨耗封严涂层有了明显改善，抗热震寿命达到400次。这与Y2O3在涂层中的“稀土元素效应”有关，稀土元素能够有效阻碍高温环境下氧向涂层内部的扩散，降低TGO层的生长速度，使TGO处界面具有良好的界面状态，使涂层具有优良的抗热震性能。（3）研究了弥散纳米Al2O3新型四相高温可磨耗封严涂层的组织结构与特性。研究发现，由于热压滤溶胶-凝胶工艺的湿化学特性本质以及氧化铝与金属基体的热膨胀系数差异，制备厚度大于0.5mm的可磨耗封严涂层难度较大，难以达到可磨耗封严涂层体系的厚度要求。针对此问题，研究了采用等离子喷涂工艺制备弥散纳米Al2O3四相可磨耗封严涂层，所制备涂层具有十分优异的可磨耗性能、抗冲蚀性能和抗热震性能，其抗热震寿命达到1900次。涂层中弥散分布的纳米Al2O3能够有效阻碍氧扩散并具有高温超塑性，有效松弛高温热应力，提高涂层的抗热震寿命。本项目研究为航空发动机涡轮外环用陶瓷基高温可磨耗封严涂层提供了新的理论和新的技术途径。