Early Peeling Failure Investigation of Thermal Sprayed Nickel-Chromium-Aluminum-Yttrium/Polyester Coating

During factory test of an aircraft engine, the thermal sprayed nickel-chromium-aluminum-yttrium (NiCrAlY)/polyester coating on the shroud ring of the high-pressure turbine peeled off prematurely, which endangered the safety of the test and caused the test to be suspended. With the purpose of revealling the root cause of coating failure and put forward solution measures, the microstructure and chemical composition of the coating after failure were analyzed by metallographic examination and energy spectrum analysis, thus the failure characteristics of the coating were obtained. The analysis results indicate that cracking along the interface between the bond coat and the substrate is the typical characteristic of coating peeling off, and interfacial contamination is an important reason for the coating to fall off from the surface of the substrate in large pieces. The root cause lies in the improper control of the abrasive blasting treatment process prior to spraying.