A Comparative Study of Spray-dried and Mechanically-mixed ZrB2-MoSi2 Composite Coatings Fabricated by Low Pressure Plasma Spray

The agglomerated ZrB2-MoSi2 composite powder was prepared by spray drying and sintering. The spray-dried ZrB2-30wt%MoSi2 (SZM) composite coating was manufactured by low pressure plasma spray (LPPS) using the agglomerated powder. For comparison, the mechanically-mixed ZrB2-30wt%MoSi2 (MZM) composite coating was also prepared by LPPS. The composite powders and the coatings were characterized by X-ray diffraction and scanning electron microscopy. The flowability and the loose density of the agglomerated powders were measured by Hall flow meter and loose density instrument, respectively. Microhardness, porosity and oxidation behavior of the coatings were also investigated. The results show that when the spray-dried powder is sintered at 1200 °C for 1 h, its flowability and loose density are up to 25.8 s/50 g and 1.12 g/cm3, respectively. The distribution of MoSi2 phase in SZM coating is much more uniform than that in MZM coating. Additionally, the SZM coating exhibits a high compactness and much better oxidation-resistance at 1500 °C compared to the MZM coating.