热喷涂粘结层的表面氧化膜全周期高温演变行为及抗氧化强化新方法

The growth and the complex stress of thermally grown oxide (TGO) on thermally sprayed bond coat determine the degradation and failure of thermal barrier coatings. Therefore, to improve the oxidation resistance of bond coat and reduce the growth rate of TGO is a key issue towards the development of advanced thermal barrier coatings. Based on the observation that the TGO has been formed on the as-sprayed bond coat, in this proposal, the whole evolution of TGO from as-sprayed condition to the high temperature service condition is defined as an intergrated TGO evolution, and the detailed evolution mechanisms during the pre-treatments of bond coat will be explored. The aim of this proposal is to develop the intergrated TGO structure evolution theory and propose novel approaches to improve the oxidation resistance of bond coat. The contents include the following issues. Firstly, the dependence of TGO structure of as-sprayed bond coat on the coating deposition parameters will be clarified, and this would provide the initial information for the research on the TGO evolution. Secondly, the control mechanism of TGO grain size on the TGO growth kinetics will be explored based on revealing the TGO thickening behaviour at high temperature. Thirdly, the discretization mechanism of TGO by through-thickness cracking and in-plane shrinking during pre-diffusion will be explored, and the restructuring mechanism of TGO by in-plane growth during pre-oxidation will be revealed. Finally, the intergrated TGO structure evolution theory will be established, and novel approaches to improve the oxidation resistance of bond coat through the coating deposition and pre-treatment will be developed. This project would provide scientific support towards the development of advanced thermal barrier coatings and oxidation resistant coatings for high temperature applications.

热喷涂粘结层表面氧化膜(TGO)增厚及其应力主导着热障涂层损伤及失效。因此，强化粘结层抗氧化性、降低TGO生长速度，是发展先进热障涂层的关键。本项目着眼于“热喷涂粘结层表面氧化膜在喷涂态业已存在”，将TGO从喷涂态到最终高温服役的全过程融合为TGO演变的全周期，研究揭示粘结层预处理过程的核心过程机理，研究目标在于发展TGO全周期演变理论并提出提高粘结层抗氧化性能的新方法。研究内容有：首先，研究喷涂态粘结层TGO结构对制备方法的依赖关系，为TGO演化研究提供组织基础；其次，阐明高温下TGO增厚规律，揭示晶粒尺寸对TGO生长动力学的控制机理；再次，针对预扩散揭示TGO纵裂与横缩离散化机理，针对预氧化揭示TGO重构机理；最后，形成系统的TGO全周期高温演变行为理论，并提出降低TGO生长速度的粘结层制备和处理调控新方法，为发展先进热障涂层提供科学依据，对发展其它高温抗氧化涂层也具可资借鉴的意义。

提高合金涂层抗高温氧化性能，是发展高性能粘结层与长寿命热障涂层的关键。本项目将涂层热生长氧化膜（TGO）从喷涂态到高温服役的全过程定义为TGO演变的全周期，构建了TGO全周期演变理论，发展了提高抗氧化性能的涂层预氧化新方法。具体进展如下：首先，研究了喷涂态粘结层TGO结构对制备方法的依赖关系，明确了大气等离子喷涂、超音速火焰喷涂、真空等离子喷涂依次降低涂层氧化的规律，为制备高品质低氧化粘结层提供了基础；其次，阐明了高温下TGO生长动力学规律，揭示了晶粒尺寸对TGO生长动力学的控制机理，晶粒尺寸增大有利于减少晶界数量从而降低氧化速率；进一步，提出涂层预氧化新方法，将多层细晶TGO转变为单层大晶粒TGO，从而显著降低氧化速率、提高抗氧化性能，揭示了TGO的纵裂、横缩离散化和粗晶化重构机理；最后，构建了系统的TGO全周期高温演变行为理论，形成了显著降低TGO生长速率的粘结层预氧化新方法，制备的MCrAlY涂层1000℃氧化速率常数在公开报道数据中最低，即抗氧化性能达到最高水平。相关成果在Corrosion Science等本领域高水平期刊发表论文8篇，应邀做大会特邀报告6次和分会邀请报告3次。项目成果应用于东方汽轮机公司，指导制备高性能粘结层和热障涂层，支撑了我国首台自主F级重型燃气轮机热部件研制，未来对发展航空航天发动机高温抗氧化涂层也具有借鉴意义。