Restrained TGO growth in YSZ/NiCrAlY thermal barrier coatings by modified laser remelting

Abstract

Abstract Thermal barrier coatings (TBCs) are widely applied in high temperature gas turbines and jet engines to protect the superalloy components. Due to oxygen transfer through topcoat and the oxidation of bond-coat alloy, a thin layer of thermally grown oxide (TGO) will generate between the ceramic topcoat and the metallic bondcoat of TBCs after long-term operation. Cracking and spalling are often observed at the topcoat-TGO and TGO-bondcoat interfaces since the thickening of TGO layer may lead to strong tensile stress. Previously, laser remelting process has been developed as an effective way in restraining the TGO growth. In the present research, preheating laser remelting and sol-gel repairing laser remelting were respectively employed to further decelerate the TGO growth by reducing the number density and average size of vertical cracks in the topcoat. After 100 h isothermal oxidation, the TGO growth rate of the modified laser remelted specimens are much lower than the conventional laser remelted specimens, which shows the potentiality of preheating and sol-gel repairing as effective promotions of laser remelting process in restraining the TGO growth.