Influence of gas shroud on property of plasma sprayed thermal barrier coating

The comparative study were carried out on the microstructure as well as the properties of the coating prepared by atmospheric plasma spraying and shroud plasma spraying. The results showed that, compared to the conventional atmospheric plasma sprayed(APS) coating, the shroud plasma sprayed(SPS) coating contained less unmelted or partially melted particles and oxide content, and porosity was lower. The SPS coating presented superior oxidation resistance at 1080℃ than the APS one. The reason owed to the mitigation of the involvement of the surrounding air that caused turbulent of the plasma, consequently,the particles were more fully melted and less oxide formed in the coating. The finally deposited SPS coating was denser and contained more Al element, which induced the formation of compact Al₂O₃ layer at the early stage of oxidation. This compact Al₂O₃ layer would slow down the thickening rate of thermally grown oxide(TGO) that provides better resistance to the bond layer,therefore the SPS coating presents higher resistance to high temperature oxidation.