等离子喷涂工艺参数对GdPO4热障涂层组织结构和结合强度的影响

随着航空发动机涡轮进口温度提升,目前最广泛使用的Y₂O₃部分稳定ZrO₂(YSZ)热障涂层(TBCs)已难以满足需求,亟须发展新一代超高温TBCs。GdPO₄是一种极具应用前景的TBCs材料。本工作采用等离子喷涂方法制备GdPO₄/YSZ双陶瓷层结构TBCs,研究喷涂工艺参数特别是喷涂功率对GdPO₄陶瓷涂层相组成、表面形貌、微观结构以及结合强度的影响。结果表明:等离子喷涂GdPO₄过程中会有元素P损耗,得到的涂层除了GdPO₄外,还有一些Gd₃PO₇相;随着喷涂功率降低,Gd₃PO₇相含量减少;GdPO₄陶瓷涂层的主体结构由充分熔融的喷涂粒子堆垛构成,其中镶嵌有未熔化粒子构成的微区;随着喷涂功率降低,未熔化微区增多,涂层厚度降低;GdPO₄/YSZ TBCs的结合强度随喷涂功率降低而减小,主要是由于未熔化微区增多降低了涂层的内聚力;因此,低喷涂功率不利于涂层的结合强度。

Effects of air plasma spraying parameters on microstructure and bonding strength of GdPO4 thermal barrier coatings

With the increase of the turbine inlet temperature of gas engines, the widely used Y2O3 partially stabilized ZrO2（YSZ）thermal barrier coatings (TBCs) have been unable to meet the requirements, and new generation TBCs that can survive ultra high-temperatures are urgently needed. Among many TBC candidates, GdPO4 has a great application prospect. In this study, GdPO4/YSZ TBCs were prepared by air plasma spraying, and the effects of preparation parameters, especially spraying power on the phase composition, surface morphology, microstructure and bond strength of GdPO4 coatings were investigated. The results show that the P loss takes place during spraying, and both GdPO4 and Gd3PO7 phases are detectable in the final topcoats, the content of the latter decreases by reducing the spraying power. The GdPO4 coating microstructure is mainly composed of piles of fully melted spray particles, among which there is porous micro-zone consisting of unmelted particles. With the decrease of the spraying power, the content of the micro-zone increases, and the coating thickness significantly decreases. The bonding strength of GdPO4/YSZ TBCs decreases with the decrease of spraying power, which is mainly because the cohesion of coating decreases with the increase of unmelted micro-zone. Therefore, low spraying power is not beneficial to the coating bonding strength.