Zr/Re共改性PtAl涂层在恒温氧化中组织演变研究

Microstructure Evolution of Zr/Re Co-modified PtAl Coatings During Isothermal Oxidation

摘要:

采用电镀Pt真空扩散退火，复合电镀Ni-Zr/Re层+电弧离子镀Al层真空扩散退火的方法制备了Zr/Re共改性PtAl涂层，并对其在1100 ℃进行200 h的恒温氧化实验。使用SEM、XRD、EPMA对退火态涂层、氧化态涂层的物相组成以及显微形貌进行表征，探究氧化过程中改性元素的分布以及涂层组织的演变规律。结果表明，涂层中弥散分布的富Re析出相在氧化过程中聚集长大并形成挥发性氧化物Re₂O₇。固溶在涂层中的Zr与扩散到涂层中的基体合金元素Ta发生了共析出，并且部分Zr进入Al₂O₃膜中形成富Zr氧化物，降低Al₂O₃膜的生长速率。此外，随着涂层和基体之间元素互扩散，涂层中的β相发生马氏体相变，互扩散区中的析出相由片状结构转变为颗粒状，同时在涂层的二次反应区中发现富Cr析出相和富Re、Cr和W析出相存在共生关系。

Abstract:

The Zr/Re co-modified PtAl coating was fabricated by electroplating Pt vacuum diffusion annealing and composite electroplating Ni-Zr/Re layer+arc ion plating Al layer vacuum diffusion annealing. The isothermal oxidation experiment was carried out at 1100 ℃ for 200 h. The phase composition and microstructure of the as-annealed coating and the oxidized coating were characterized by SEM, XRD and EPMA, and the distribution law of the modified elements and the evolution law of the coating microstructure during oxidation were investigated. The results show that the Re-rich precipitates dispersed in the coating aggregate and grow during oxidation and form volatile oxide Re₂O₇. The Zr solid-solved in the coating co-precipitates with the Ta element diffused into the coating from the substrate alloy, and some Zr enters the Al₂O₃ scale to form Zr-rich oxides, reducing the growth rate of the Al₂O₃ scale. In addition, with the mutual diffusion of elements between the coating and the substrate, the β phase in the coating undergoes martensitic transformation. The precipitates in the mutual diffusion zone change from plate-like to particle-like, and the coexistence relationship of Cr-rich precipitates and Re, Cr and W-rich precipitates is found in the secondary reaction zone of the coating.