CHARACTERIZATION OF NANOSTRUCTUREDYTTRIA STABLIZED ZRCON ATHERMAL BARRER COATINGS DEPOSITED BY ATMOSPEERC PLASMA SPRAYING

Thermal barrier coatings (TBCs) are extensively used in gas turbine engines to reduce the surface temperature of hot-section metal components. Creation of nano-structure is a new approach to fabricate of modern TBCs. The main goal of this investigation is fabrication and characterization of two layer TBC including nanostructured yttria stabilized zirconia (YSZ) top coat and NiCoCrAIY bond coat on the superalloy substrate. For this scope, the substrates of Inconel 738LC coupons were first deposited with a NiCoCrAIY bond coat and then with nanostructured YSZ powder by atmospheric plasma spraying. Bonding strength test was carried out based on the ASTM C633-01. To evaluate thermal insulation value of coatings, the thermal insulation capability test was designed and administered. X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM) were employed to characterize the phase compositions and microstructures of the nanostructured powder and coating. Results reflect that nanostructured coating contain a bimodal microstructure consisting of nanosized particles retained from the powder and microcolumnar grains formed through the resolidification of the molten part of powder. This unique microstructure resulting in improvement of bonding strength and thermal insulation capability, so that bonding strength and thermal insulation capability obtained 42 MPa and 145°C respectively.

Keywords:

Thermal barrier coating , Nanostructure , YSZ , Atmospheric plasma spraying , Thermal insulation , Bonding strength