Thermal cycling behaviour of plasma sprayed NiCr-Al-Co-Y2O3 bond coat in thermal barrier coating system

Abstract

The aim of this study was to investigate the thermal cycling behaviour of NiCr-Al-Co-Y2O3 bond coating in thermal barrier coating (TBC) system with ZrO2-MgO as a top coating. The coatings were deposited by atmospheric plasma spraying (APS) on stainless steel X15Cr13 (EN 1.4024) substrate. The used composite powder NiCr-Al-Co-Y2O3 was mechanically cladded, and the steel substrates were preheated to 160 - 180°C. The thermal cycling performance of the obtained bond coat and the effect of formed complex ceramic oxides of the Al2O3-Y2O3 system were tested by heating to 1200°C and cooling in air to 160 - 180°C. The number of performed thermal cycles was 7, 32 and 79. The quality of the obtained coating, as well as its thermal cycling behaviour, was assessed through the microstructural analysis, microhardness and tensile bond strength measurements, and change in chemical composition and microhardness. The obtained results showed that the steel substrate, bond coat oxidation and interdiffusion at bond coat/substrate interface have a significant influence on changes in chemical composition and microhardness of the bond coat. The correlation between oxidation behaviour of NiCr-Al-Co-Y2O3 bond coat and number of thermal cycles was also discussed. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR 34028, Grant no. TR 35021 and Grant no. OI 174004]