等离子喷涂热障涂层高温 TGO 的形成与生长研究

目的研究热障涂层(TBC)和纯粘结层(BC)在1100℃下的氧化动力学,探讨热障涂层中热生长氧化物(TGO)组织结构的演化规律。方法运用大气等离子喷涂技术(APS)制备涂层,对比分析热障涂层和纯粘结层涂层在1100℃下等温氧化2,5,10,20,50,100,200,350 h后TGO的厚度变化,并对粘结层表面和热障涂层截面分别进行XRD和SEM分析。结果热障涂层和纯粘结层在1100℃下的氧化动力学均遵循抛物线规律,其氧化速率常数分别为0.344,0.354μm/h0.5。等温氧化5 h后,TGO的主要成分为α-Al2O3;随氧化时间的增加,生成Cr2O3、尖晶石、Co O和Ni O的混合氧化物;等温氧化100 h后,Co O消失,Ni O的含量减少,Cr2O3和尖晶石氧化物的含量增加;等温氧化350 h后,TGO中出现了裂纹,但涂层仍未剥落,TGO最终由顶层多孔的混合氧化物层和底层具有柱状晶结构的α-Al2O3层组成。结论顶层陶瓷层(TC)对热障涂层氧化速率常数的影响很小。TGO中α-Al2O3首先形成并以柱状结晶的方式生长,混合氧化物在α-Al2O3上形成,TGO生长速度逐渐变缓。

Formation and Growth Behavior of TGO in Air Plasma Sprayed Thermal Barrier Coatings at High Temperature

Objective To investigate growth kinetics of TBCs and pure BC as well as microstructure evolution of TGO in TBCs. Methods Variations in TGO thickness of APS-TBCs and pure BCs after isothermal oxidation at 1100 ℃ for 2,5,10,20,50,100, 200,350 h were comparatively analyzed. XRD and SEM were used to characterize the surface and cross-section of TBCs. Results TGO growth kinetics for both samples followed parabolic laws, and the oxidation rate constants of TBCs and pure BC were 0. 344μm/h0. 5 and 0. 354 μm/h0. 5 , respectively. TGO mainly consisted ofα-Al2 O3 after isothermal oxidation for 5 h. CoO, NiO, Cr2 O3 and spinel oxides appeared with the increase of oxidation time. CoO disappeared, and content of NiO reduced while contents of Cr2 O3 and spinel oxides increased after isothermal oxidation for 100 h. Cracks appeared but failure of TBCs did not occur after iso-thermal oxidation at 1100 ℃ for 350 h. TGO eventually consisted of a sub-Al2 O3 layer with columnar microstructure and the upper porous mixture. Conclusion TCs had little effect on the oxidation rate constant of BCs. α-Al2 O3 was firstly formed in TGO and grew in form of columnar crystals, then mixed oxides appeared on α-Al2 O3 and the growth rate of TGO became slow.