Processing and characterization of CYSZ/Al2O3 and CYSZ/Al2O3+YSZ multilayered thermal barrier coatings

CYSZ/Al2O3 and CYSZ/Al2O3+YSZ multilayer ceramic coatings were produced in 4, 8 and 12 layered with a total thickness of ~400μm by high-velocity oxy-fuel (HVOF) and atmospheric plasma spraying (APS) processes. Microstructure, thermal and mechanical properties were evaluated. The thickness of metallic bonding layer and total thickness of ceramic top layer were measured as 100±10μm and 400±20μm, respectively. Porosity levels of multilayer coatings were observed between 6 and 13%. Thermal conductivity values of the CYSZ/Al2O3 and CYSZ/Al2O3+YSZ coatings were in the range of 0.99 to 1.50W/mK. The bonding strength of as-sprayed coatings was increased from 5.4 to 10.1MPa for CYSZ/Al2O3, and 8.7 to 11.5MPa for CYSZ/Al2O3+YSZ coatings with the increasing number of layers. Existence of phase transformation (γ→α) for Al2O3 coating was observed after the thermal cycle test. The results indicated that the thermal conductivity and thermal cycle strength of CYSZ/Al2O3+YSZ TBCs were higher than CYSZ/Al2O3 based thermal barrier coatings. •CYSZ/Al2O3 and CYSZ/Al2O3+YSZ multilayer ceramic coatings were produced.•The thermal conductivity values of coatings were changed between 0.99 and 1.50W/mK.•Cracks or pull outs did not occur on the surface of TBCs after thermal cycle test.•The thickness of α-Al2O3 based TGO layer was between 0.5 and 1.5μm.•The bonding strength values of coatings were changed between 5.4 and 11.5MPa.