Thermal Cycle Damage Behavior of Thermal Barrier Coating System by Suspension Plasma Spraying

Abstract

Thermal barrier coatings (TBCs), consisting of a ceramic insulating top coat (TC) and metal bond coat, have been widely used in gas turbines to protect hot section metal alloy components. In general, TC is deposited by atmospheric plasma spraying (APS) method or by electron beam physical vapor deposition (EB-PVD) one . APS method provides a porous TC which has lower thermal conductivity compared with EB-PVD TBC. On the other hand, EB-PVD TBC has columnar microstructure resulting in higher resistant to thermal shock than APS TBC. Suspension plasma spraying (SPS), as a newly emerged technique, is used to deposit coatings with enhanced characteristics utilizing suspensions containing submicron spray particles. However, there are few reports of damage behavior of SPSed TBC system. In this study, the high temperature oxidation test and thermal cycle fatigue test were carried out on SPSed TBC and damage behavior was investigated comparing with APSed TBC. It was revealed form the experimental results that there were differences in the thermally grown oxide (TGO) growth behavior and damage behavior between both coatings. In particular, the TGO growth behavior suggested the superiority of coating life of SPSed TBC.