Heat treatment for TGO growth on NiCrAlY for TBC application

Abstract

The TGO (thermally grown oxide) is a layer of TBC (Thermal Barrier Coating), which develops and grows at the interface between at the bond coat (BC) and ceramic top coat (TC) in high temperature, and is composed mainly of aluminum oxides. The TGO layer improves the effective adhesion between BC/TC and effectively protects against oxidation and hot corrosion. However, this layer is the main failure of TBC and, thus, required further research. This work studied the initial growth of the TGO when exposed to NiCrAlY (BC) at high temperatures. The NiCrAlY samples obtained from its powder by isostatic pressing, sintered by hot uniaxial pressing at 1150 °C for one hour (10 MPa), and the TGO was grown by heat treatment in the air and vacuum at 800, 1100, and 1150 °C for four hours. The results indicated that with increased temperature, surface roughness increases and the oxide layers in the vacuum process are larger than in the air. SEM found that at 1100 °C, samples obtained the most appropriate oxide layer thickness. In vacuum treatments, x-ray diffraction analyses showed the formation of greater quantities of aluminum oxides.