力学载荷条件下 EB-PVD 热障涂层损伤行为研究

目的研究力学载荷条件下EB-PVD热障涂层的损伤行为。方法采用电子束物理气相沉积工艺(EB-PVD)制备热障涂层(TBCs),利用SEM和体式显微镜对力学性能试验后带涂层试样的断口特征、裂纹形貌和金相组织进行观察,分析热障涂层在拉伸、持久和旋转弯曲疲劳等典型力学载荷条件下的损伤行为。结果在室温拉伸条件下,陶瓷层内先出现垂直于应力轴、沿柱状晶簇扩展的平行环状周向微裂纹,随着拉伸塑变量的增加,局部区域裂纹贯穿粘结层并进入合金基体;900℃高温拉伸条件下裂纹也产生于陶瓷层,但裂纹均钝化于粘结层与陶瓷层的界面,并穿透粘结层。在持久条件下,试样在弹性变形阶段涂层即发生开裂,随后沿着陶瓷层柱状晶簇间扩展,但未扩展至粘结层;在高温高周疲劳条件下,裂纹首先出现在粘结层,随后向基体逐渐扩展,扩展深度较浅,而基体疲劳裂纹在粘结层裂纹末端萌生并倾斜滑移扩展。结论提高粘结层韧性、减少粘结层中裂纹萌生和向基体扩展,是热障涂层材料和工艺优化的有效途径。

Damage Behavior of Thermal Barrier Coatings Prepared by EB-PVD under Mechanical Load

Objective To study the damage behavior of thermal barrier coatings prepared by electron beam physical vapor deposition (EB-PVD) under mechanical load. Methods Thermal barrier coatings (TBCs) were prepared by EB-PVD. Fracture characteristics, crack morphology and microstructure were analyzed by SEM and stereo microscope. Tensile properties, stress rupture properties and rotary bending fatigue properties were studied under typical mechanical load conditions. Results The results showed that micro-cracks occurred in ceramic layers and entered the carbide of matrix during elastic plastic deformation. Destructive cracks occurred in the adhesive layer in the tensile testing at room temperature, but not at high temperature. Under stress rupture conditions, cracks started from the elastic deformation stage, then expanded along the clusters of column grains of TBC, but did not extend into the adhesive layer. Cracks first appeared in the adhesive layer, followed by expansion to the matrix in the rotary bending fatigue properties testing. Fatigue cracks on the matrix initiated at the end of cracks in the adhesive layer and sloping sliding extension occurred. Conclusion Improving the toughness of the bonding layer, and reducing crack initiation in the bonding layer and its extension to the matrix, are effective ways for optimization of thermal barrier coating materials and process.