ZrCr梯度界面层对Zr/Al2O3涂层体系抗热震性能影响及机理研究

Effect and mechanism of ZrCr gradient interfacial layer on thermal shock resistance of Zr/Al2O3 coating

摘要:

采用中频磁控溅射和超音速等离子喷涂依次在锆合金(Zr-4)基体表面制备了Zr(84.61 at.%)Cr/Zr(17.39 at.%)Cr/Al₂O₃(ZrCr梯度界面层)和Al₂O₃ (无ZrCr梯度界面层)涂层。利用XRD、SEM和HRTEM等重点分析了ZrCr梯度界面层对Zr-4/Al₂O₃涂层界面微观结构、结合强度和抗热震性能的影响。研究结果表明：通过增设ZrCr梯度界面层,能显著提升Zr-4/ZrCr/Al₂O₃体系结合强度至50.3±2.52 MPa,较Zr-4/Al₂O₃体系结合强度值提升约46%；循环热震条件下,Zr-4/ZrCr/Al₂O₃体系膜基界面完整,与ZrCr梯度界面层能显著提升界面结合强度且喷涂及热震实验过程中ZrCr梯度界面层Cr原子优先形成较致密的Cr₂O₃能进一步有效抑制氧扩散至Zr-4有关；Zr-4/Al₂O₃膜基界面则出现明显开裂甚至剥离行为,其主因是Zr-4/Al₂O₃两者界面热应力集中而导致Zr-4/Al₂O₃界面开裂；HRTEM和EDS线扫描结果证实在Zr-4/Al₂O₃界面开裂处形成的疏松ZrO₂氧化物是后续热震循环中进一步加剧涂层大面积剥落失效的根本原因。

Abstract:

In this paper, two coatings (Zr(84.61 at.%)Cr/Zr(17.39 at.%)Cr/Al₂O₃ and Al₂O₃ without ZrCr gradient interfacial layer) were fabricated by intermediate frequency magnetron sputtering and supersonic plasma spraying on zirconium alloy (Zr-4) substrate. The influence of ZrCr gradient interfacial layer on the interface microstructure, adhesiveSstrength and thermal shock resistance of two coatings was studied by XRD,SEM and HRTEM. The results show that the adhesiveSstrength of Zr-4/ZrCr /Al₂O₃ system can be significantly increased to 50.3±2.52 MPa about 46% higher than that of Zr-4/Al₂O₃ system by adding ZrCr gradient interfacial layer. In the process of thermal shock test, It is found that the interface of Zr-4/ZrCr/Al₂O₃ system remian intact because of its higher adhesiveSstrength and formation of dense Cr₂O₃ in ZrCr gradient transition layer protecting Zr-4 substrate from oxidation. The interface of Zr-4/Al₂O₃ system, however, appears obvious cracking or even peeling behavior, the main reason is that thermal stress concentration in the interface of Zr-4/Al₂O₃ system leads to Zr-4/Al₂O₃ interface cracking. In the process of subsequent thermal shock test, the formation of loose ZrO₂ at the Zr-4/Al₂O₃ interface cracking confirmed by HRTEM and line scanning results was the root cause for aggravating the large-scale peeling to failure of the coating.