Effect of Heat Treatment on Plasma-Sprayed Zircon (ZrSiO ZrSiO4)

The effect of heat treatment on the structure and properties of a plasma-sprayed zircon coating was evaluated. The as-sprayed coating, with open porosity of 10%, is composed of t-ZrO 2 and amorphous SiO 2 After heat treatment at 1473 K, ZrO 2 grows in columnar shape perpendicular to the coating surface, while SiO 2 crystallizes to cristobalite. The open porosity decreases to about 5% after the heat treatment. This can be attributed to the sintering of SiO 2 and the phase transformation of zirconia. When heat-treated at 1673 K, the coating is composed of ZrSiO 4 with dispersed fine m-ZrO 2 The open porosity increases again up to 10%. The thermal conductivity of the zircon coating increases with increasing heat treatment temperature.