蜂窝结构中间层对元素互扩散及界面结合强度的影响

Intensive element interdiffusion impairs the mechanical properties of the substrate alloys and degrades the overlayer coatings. Developing a diffusion barrier between the coating and the substrate is an effective method to limit the interdiffusion. However, it has been a long-term unresolved problem how to make a diffusion barrier with excellent barrier ability and strong interfacial strength. Such a problem also hinders the application of diffusion barrier in the field of high temperature protective coatings. Based on Fick's laws and research experiences in active and metal-oxide diffusion barriers, an interlayer with honeycomb structure is proposed as a diffusion barrier in the present work. Fast surface diffusion of alloy elements from the overlyer to the interlayer through the honeycombs will enhance the interfacial strength with the help of interfacial interlock. α-Al2O3 formed during high temperature treatment can act as an excellent barrier to the interdiffusion. The work will establish the relationship of the interfacial strength with the structure parameters (pore diameter , wall thickness, pore depth and oxide thickness) of the honeycomb, and the barrier ability with the grain size and grain density of the diffusion barrier. The influence of interdiffusion behavior, interfacial residual stress, microstructures of interdiffusion zone and thickness of the diffusion barrier on the interfacial strength will be discussed with the calculated impact weights and the established mechanism. Then, optimized parameters of the structure and properties of the diffusion barrier will be obtained. The result will help to develop a diffusion barrier with excellent barrier ability and strong interfacial strength. It will provide credible experimental evidences for the application of a diffusion barrier on high temperature coatings and deepen understanding of the Fick's laws.

不加控制的元素互扩散会降低基体合金的性能，加剧表面涂层的退化。在涂层和基体间加入阻扩散层是抑制元素互扩散的有效方法。如何获得既有强元素扩散阻挡能力，又有高界面结合强度的阻扩散层，是一个长期未解决的问题，也是限制阻扩散层应用的关键问题。本项目以Fick扩散理论为指导，在已有"活性"阻扩散层和金属-氧化物阻扩散层的研究基础上，提出用蜂窝结构中间层，促使元素表面扩散，加强界面咬合，提高界面结合强度；形成α- Al2O3阻扩散层，抑制元素的互扩散。研究蜂窝结构参数(孔径，孔深，壁厚和膜厚)与界面结合强度、阻扩散层微观结构与扩散阻挡能力之间的关系；弄清元素互扩散、界面残余应力、阻扩散层厚度和互扩散产物对界面结合强度的影响，阐明其作用机理和影响权重；实现阻扩散层结构和性能的优化。研究结果将促进强界面结合和高阻挡能力阻扩散层的开发，为阻扩散层在高温防护涂层中的应用提供参考，将加深人们对扩散理论的认识。

不加控制的元素互扩散会降低基体合金的性能，加剧表面涂层的退化。在涂层和基体间加入起阻挡元素扩散作用的中间层是有效的方法。本项目以Fick扩散理论为指导，在已有“活性”阻扩散层和金属-氧化物阻扩散层的研究基础上，设计并由阳极氧化和微弧氧化技术分别制备了蜂窝结构的中间层，通过调整阳极氧化时的溶液浓度、温度、电流密度或微弧氧化的电压、频率、占空比及处理时间等，获得了以α-Al2O3为主的阻扩散层；研究了合金元素在蜂窝结构及其他结构中间层的扩散，建立了相应的模型，分析了影响中间层元素扩散阻挡能力的因素；讨论了元素互扩散、中间层厚度、界面应力和界面产物等与复合涂层界面结合强度之间的关系；获得了蜂窝结构参数优化的阳极氧化及微弧氧化工艺，计算了合金元素在蜂窝结构层的扩散系数，并制取了具高温抗氧化抗热腐蚀和强界面的含蜂窝结构中间层的复合涂层。上述研究结果为开发阻扩散层提供了重要的科学依据，大大拓宽了人们对扩散理论的认识。本项目至结题时已发表了标注资助论文18篇，其中在SCI/EI源刊发表11篇，申请了国家发明专利11项，获得授权6项。