Hot isostatic pressing of plasma sprayed yttria-stabilized zirconia

The porosity in plasma sprayed ceramics is caused by the irregular splat formation of the lamellae structure as the molten droplets impact the substrate. This paper reports the influence of hot isostatic pressing (HIP) as a post-spray treatment of plasma sprayed coatings. Investigations are made on the physical properties, pore size distribution and thermo-physical properties, namely thermal diffusivity and thermal conductivity, of plasma sprayed yttria-stabilized zirconia (ZrO₂-7.8 wt% Y₂O₃) coatings after HIP at 1000, 1100 and 1200°C for 1 h. Results show that HIP processing the plasma sprayed coatings reduced the porosity by ∼2.5% and increased the microhardness by ∼40%. Correspondingly, the thermal diffusivity and thermal conductivity of the coatings were found to be significantly changed after HIP treatment at 1200°C.