Development of Yttria-Stabilized Zirconia and Graphene Coatings Obtained by Suspension Plasma Spraying : Thermal Stability and Influence on Mechanical Properties

This work investigates the feasibility to deposit graphene nano-platelets (GNP)-reinforced yttria stabilized zirconia (YSZ) composite coatings. The coatings were deposited from an ethanol-based mixed YSZ and GNP suspension utilizing suspension plasma spray (SPS) process. Raman spectroscopy confirmed the presence of GNPs in the YSZ matrix and SEM analysis revealed a desired columnar microstructure with GNPs distributed predominantly in the inter-columnar spacing of the YSZ matrix. The as-deposited YSZ-GNP coatings were subjected to different isothermal treatments, i.e. 400, 500 and 600 °C for 8 hours, to study the thermal stability of GNPs in the composite coating. Raman analysis showed the retention of GNPs in specimens exposed up to a temperature of 500 ºC, although the defect concentration in the graphitic structure increased with an increase in temperature. Only a marginal effect on the mechanical properties (i.e. hardness and fracture toughness) was observed in the isothermally treated coatings. The results included in this work can open up new opportunities for thermally sprayed graphene-containing coatings to be used in various functional applications