粗糙度对热障涂层冲蚀失效的影响及模型建立

采用气体喷砂试验机研究了大气等离子喷涂(APS) ZrO₂-7%Y₂O₃(7YSZ)热障涂层的冲蚀失效机理, 分析了陶瓷层表面粗糙度对热障涂层冲蚀磨损率及失效行为的影响, 研究了基于多孔层状的热障涂层在常温高速粒子90°攻角下的冲蚀失效特征, 探讨了多孔层状结构对涂层冲蚀失效演变机制的作用, 此外, 建立了基于粗糙度的冲蚀失效数学模型。研究结果表明: 冲蚀磨损率与陶瓷层表面粗糙度呈线性递增关系; 涂层在高速粒子冲蚀下多孔层状结构加剧了涂层的冲蚀失效; 涂层表面在粒子冲蚀下承受着非均匀、非连续的压-压脉动循环载荷, 在微凸粗糙表面承载着正应力和切应力的相互作用; 正应力迫使涂层出现凹坑, 切应力易导致涂层出现沟槽, 并同时以原喷涂态表面网状裂纹为策源地诱发裂纹在粒子晶界和层间界面萌生扩展导致涂层产生粒子和片状剥落, 最终涂层显示出典型的磨粒磨损和低周疲劳失效形式。

Erosion Failure Mechanism and Model Establishment of Thermal Barrier Coatings Based on Roughness

Erosion failure mechanism of atmospheric plasma sprayed (APS) ZrO₂-7%Y₂O₃ (7YSZ) thermal barrier coatings (TBCs) was studied with a san-blasting erosion tester. The failure features of TBCs with laminar and porous structure were investigated using impingement angle 90° at room temperature. Effect of porous and laminar structure on erosion rate was analyzed. Moreover, regarding the failure factors, the relation of ceramic coating roughness and erosion rate was analyzed and their mathematic model was established. The experimental results indicate that the factors of porous and laminar structures play an important role in crack propagation in TBCs. For the TBCs with ununiform, discontinuous pressure-pressure pulsating cyclic load under impact of high velocity particles, the ceramic coatings are loaded with normal stress and shear stress, in which the normal stress leads to appearance of pit in ceramic coating and the shear stress leads to grooves. Meanwhile, the crack propagation in grain boundaries and interfaces of laminar structure will appear based on the net cracks on ceramic coating surface in sprayed TBCs, which will lead to particle exfoliation and flaky debris. So the erosion failures of TBCs follows abrasive wear and low cycle fatigue mode. The relevance between ceramic coating roughness and erosion rate indicates an increased linear relation.