HOT ISOSTATIC PRESSING OF PLASMA-SPRAYED YTTRIA-STABILIZED ZIRCONIA

The porosity in plasma sprayed ceramics is caused by the irregular spl at formation of the lamellae structure as the molten droplets impact t he substrate. This paper reports the influence of hot isostatic pressi ng (HIP) as a post-spray treatment of plasma sprayed coatings. Investi gations are made on the physical properties, pore size distribution an d thermo-physical properties, namely thermal diffusivity and thermal c onductivity, of plasma sprayed yttria-stabilized zirconia (ZrO2-7.8 wt % Y2O3) coatings after HIP at 1000, 1100 and 1200 degrees C far I h. R esults show that HIP processing the plasma sprayed coatings reduced th e porosity by similar to 2.5% and increased the microhardness by simil ar to 40%. Correspondingly, the thermal diffusivity and thermal conduc tivity of the coatings were found to be significantly changed after HI P treatment at 1200 degrees C. (C) 1998 Elsevier Science B.V.