热障涂层体系中的氧化局域化及其成因

热生长氧化层的形貌影响热障涂层体系中应力应变分布,从而决定热障涂层体系的最终失效形式.研究了热生长氧化层中钉子或瘤状的局部突起物,即有可能造成应力集中的微区氧化局域化现象,采用扫描电镜(SEM)观察热生长氧化层的形貌,采用EDS能谱仪分析氧化局域化区域的成分.结合热障涂层体系的氧化机制,从材料学的角度分析了出现氧化局域化的原因,探讨了氧化局域化的出现对热障涂层体系力学性能的影响.结果表明,氧化局域化是由下列因素引起的:(1)活性元素的钉扎效应;(2)裂纹或者微孔洞等缺陷的诱导;(3)尖晶石的快速生长.氧化局域化的出现对热障涂层力学性能的影响同时存在有利和有害的一面.

Cause Leading to Oxidation Localization in Thermal Barrier Coating System

The cause for the oxidation localization which could lead to stress concentration in thermally grown oxide(TGO) layers of thermal barrier coatings was investigated.Thus the morphology of the TGO layer was observed using a scanning electron microscope,with the nail and lump-like protrusions to be focused on.The elemental composition in the oxidation localization zone was determined using an energy dispersive X-ray spectrometer.The cause leading to the oxidation localization was analyzed with respect to materials science,with the oxidation mechanism of the thermal barrier coating being accounted for as well.Moreover,the influence of the oxidation localization on the mechanical properties of the thermal barrier coatings was also examined.It was found that the oxidation localization of the thermal barrier coatings was mainly attributed to the anchoring effect of the active elements,the inducement of the defects such as cracks and micro-holes,and the quick growth of spinel phase.In general,the oxidation localization could be either helpful or harmful in terms of its effect on the mechanical properties of the thermal barrier coatings.