Comparative study on thermal cyclic resistance of glass-ceramic-bonded TBC system and conventional TBC system

Thermal barrier coatings (TBCs) are provided to protect the metallic parts of gas turbines from high inlet temperature. In the present study, two types of TBCs, namely conventional TBC having NiCoCrAlY bond coat, 8-YSZ top coat and a new TBC with glass-ceramic bond coat keeping the top coat same, were considered to investigate their thermal cyclic resistance at 1000celcius for 500 cycles. Assessment of weight change, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analysis were performed for both TBCs after thermal cycling. Weight change measurement indicated that oxidative weight gain dominated over the coating spallation in case of conventional TBCs. On the contrary, oxidative weight gain could not considerably govern over coating spallation for glass-ceramic bond-coated TBCs. Furthermore, thermally grown oxide (TGO) layer was not observed at the bond coat-top coat interface of glass-ceramic bond-coated TBC system whereas the same was observed clearly at the interfacial region of bond coat and top coat of conventional TBC system after completion of 500 cycles at 1000 degrees C.