热循环对热障涂层力学性能的影响

Effect of thermal cycling on mechanical properties of thermal barrier coatings

通过纳米压痕仪测试了热障涂层(TBCs)在1050℃热循环不同时间后的弹性模量和硬度,从微观层面了解其高温力学性能变化。采用X射线衍射仪(XRD)和扫描电镜(SEM)等对涂层的物相和形貌进行了分析。结果表明:采用纳米压痕仪测得Y_(2)O_(3)部分稳定的ZrO_(2)(YSZ)陶瓷层的弹性模量(Ei)在80~170 GPa之间,硬度在2.6~5.8 GPa之间。陶瓷层的硬度和弹性模量均随热循环时间增加而增加,在热循环初期,涂层的强度稍高,随着热循环时间的增加,涂层的强度减小,韧性变得更好。热循环后期,涂层的强度最大。同时,随着热循环时间的增加,划痕形貌发生了明显的变化。热障涂层的失效分析表明:由于氧化循环次数增加,YSZ发生了烧结,在热循环作用下样品内部的内应力升高,产生横向裂纹,从而导致柱状晶结构发生破坏而产生失效。

Elastic modulus and hardness of thermal barrier coatings(TBCs)after thermal cycling at 1050℃for different time were measured by nano indentation instrument,and the changes of high temperature mechanical properties were understood from the micro level.The phase and morphology of the coating were analyzed by X-ray diffraction(XRD)and scanning electron microscopy(SEM).The results show that the elastic modulus(Ei)of Y2 O3 partially stable ZrO2(YSZ)ceramic layer is between 80-170 GPa and the hardness is between 2.6-5.8 GPa.The hardness and elastic modulus of the ceramic layer increase with the increase of thermal cycle time.At the beginning of thermal cycle,the strength of the coating is slightly higher.With the increase of thermal cycle time,the strength of the coating decreases and the toughness becomes better.At the later stage of thermal cycle,the strength of the coating is the highest.At the same time,the scratch morphology changes significantly with the increase of thermal cycle time.The failure analysis of thermal barrier coating shows that YSZ is sintered due to the increase of oxidation cycle times.Under the action of thermal cycle,the internal stress in the specimen increases and transverse cracks occur,resulting in the failure of columnar crystal structure.