Microstructure and Oxidation Resistance of Thermal Barrier Coatings with Different Ceramic Layer

Abstract

Thermal barrier coatings are widely used for protection of gas turbine parts against high temperature oxidation and hot corrosion. In present work the microstructural assessment of TBCs produced by atmospheric plasma spray (APS) method was conducted. Three types of ceramic powders were used: magnesia- stabilized zirconia oxide (Metco 210), yttria stabilized zirconia oxide (YSZ -Metco 204) and fine-grained YSZ – Metco 6700. As a base material the Inconel 713 was used as well and CoNiCrAlY was plasma sprayed (APS) as a bond coat. The thickness of all ceramic layers was in range 80 – 110 μm. The elemental mapping of cross-section of magnesia-stabilized zirconia showed the presence of Mg, Zr and O in outer layer. In the YSZ ceramic layer the Y, Zr and O were observed during elemental mapping. The isothermal oxidation test was conducted at 1100 °C for 500 h in static laboratory air. On all samples the delamination and spallation of ceramic layers was observed. Chemical composition analysis of coatings showed the presence of two areas: the first one contained elements from bond coats: Ni, Cr, Al, Co and second area contained O, Cr Co and O that suggest the scale formation. The obtained results showed the total degradation of all ceramic layers as a result of internal stresses in bond-coat. Microscopic analysis showed the areas with complete degradation of bond coats and formation of thick oxides layer.