A comparative study of spray-dried and mechanically-mixed ZrB2-MoSi2 composite coatings fabricated by LPPS

Abstract:

In this work, the agglomerated ZrB2-MoSi2 composite powders were successfully 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 powders. For comparison, the mechanically-mixed ZrB2-30wt.%MoSi2 (MZM) composite coating was also prepared by LPPS. The composite powders and coatings were characterized by X-ray diffraction and scanning electron microscopy. The mobility and loose density of the agglomerated powders were measured by hall flowmeter and loose density instrument, respectively. Microhardness, porosity and oxidation behavior of the coatings also were investigated. The results show that, when the spray-dried powders were sintered at 1200℃ for 1 h, The mobility and loose density were up to 25.8 s/50g and 1.12 g/cm3, respectively. The MoSi2 phase of SZM coating distributed much more uniformly than that of MZM coating. Additionally, the SZM coating had high compactness and much better oxidation-resistance at 1500℃ compared to the MZM coating.

Key words:ZrB2-MoSi2; low pressure plasma spray; oxidation; C/C composites