硬质颗粒重复冲击TiN/Ti涂层损伤分析

航空发动机压气机叶片表面制备硬质涂层可显著提高其抗砂尘冲蚀性能,但砂粒高角度冲击对涂层损伤严重,易出现脆性裂纹。采用受控动能型重复冲击设备模拟硬质颗粒对涂层的高角度冲击,研究调制比、层数结构对TiN/Ti涂层冲击损伤的影响,并根据涂层损伤特征、冲击力学响应以及应力分布分析涂层的破坏机理。结果表明,TiN/Ti涂层出现剥落和圆周裂纹;硬质层内部、硬质层与结合层/过渡层界面存在高的应力梯度,而冲击坑点边缘硬质层上表层受到拉应力且由于材料堆起,在重复冲击下将导致涂层的疲劳剥落和圆周疲劳裂纹。调制比、层数显著影响涂层冲击响应过程,其中不同调制比的2层涂层,调制比为3:1的抗冲击性能较好;调制比为9:1的不同层数涂层,4层结构的抗冲击性能较好。

Damage Analysis of TiN/Ti Coatings Under Cycling Impact with Hard Particles

Hard thin coatings deposited on blades of the compressor of an aircraft engine can improve the anti-erosion performance; however, the coatings hardly protect particle damage with a high impact angle and brittle cracks occur easily. A kinetic energy controlled cycling impact test was applied to simulate the normal impact to coatings. The influence of the volume fraction and layers on the impact damage of TiN/Ti coatings was investigated. The failure mechanism of coatings was analyzed through damage characteristics, impact mechanics response, and stress distribution. The results show that spalling and circular crack failures occur in TiN/Ti coatings. The spalling and circular cracks are induced by high stress gradient existing in the hard layer and the interface between the hard layer and the adhesive/transition layer, tensile stress in the upper surface of the hard layer at the edge of the impact zone, and material pilling under cycling impacts. The impact dynamic response remarkably differs with volume fractions and layers. The bilayer coating with a volume fraction of 3:1 shows better anti-impacting performance among different volume fractions, and the coatings with 4 layers shows better anti-impact performance among different layers sharing the same volume fraction of 9:1.