Effect of Y2O3 Doping on Microstructure and Phase Structure of Plasma-Sprayed ZrSiO4 Coatings

ZrSiO4 and Y2O3 doped ZrSiO4 coatings were successfully prepared by atmospheric plasma spraying. The microstructure, mechanical properties and sintering behavior at 1300. of coatings were investigated. The results show that plasma-sprayed ZrSiO4 coating is mainly composed of ZrSiO4, t-ZrO2, a small amount of m-ZrO2 and amorphous SiO2 phases, while the ZrSiO4-5%Y2O3 coating contains c-ZrO2, a small amount of ZrSiO4 phase and amorphous SiO2. Compared with ZrSiO4 coating, Y2O3 doping slightly improves the hardness and fracture toughness of ZrSiO4-5%Y2O3 coating. After sintering at 1300. for 48 h, (t,m)-ZrO2 reacts with amorphous SiO2 to form new ZrSiO4 phase in plasma-sprayed ZrSiO4 coating accompanied by volume shrinkage, resulting in a large number of pores and cracks in the coating. In contrast, c-ZrO2 phase and ZrSiO4 phase are the main phases in the ZrSiO4-5%Y2O3 coating. The addition of Y2O3 helps the ZrO2 in the coating to maintain the cubic phase (c-ZrO2), which improves the high-temperature phase stability of ZrO2.