Analysis of Thermal Barrier Coating Peeled off Blade

It is found that the thermal barrier coating has peeled off the blade after test running. Macro and micro observation, micro-hardness, chemical analysis were carried out to analyze the failure blade and contrast parts. At the same time, the whole production process was investigated carefully and doing the proof test. Finally, the root cause of the fracture coating was founded. The results show that the peeling of thermal barrier coating on the blade was caused by the following reasons. The pumping rate of the equipment decreased, resulting in a decrease in the vacuum degree in the furnace. Therefore, a significant difference between the columnar crystal structure of the ceramic layer and the normal structure was created, and there was a TGO layer with certain thickness formed between the ceramic layer and the metal bonding layer. Aforementioned factors led to the declined affinity. Through changing the vacuum degree in the furnace, it can produce two kinds of columnar crystal. When the vacuum degree is high, the columnar crystal is the featheriness or ear of wheat shape and the micro-hardness is high. Whereas, the columnar crystal shows the “lamellar” and the foot is loosen, micro-hardness is low. The vacuum degree has impacted on the thermal barrier coating of microstructure and property.