Effect of spray parameters on microstructure of plasma sprayed wollastonite coatings

Wollastonite coating was prepared by plasma spraying at different spraying distances, primary gas flow rates and plasma power. The microstructure of the coating lager was examined by scanning electron microscope (SEM). The results show that the three spraying parameters affect the microstructure of wollastonite coatings greatly. Flatten degree of molten powder decreased and the number of pores increased with the increment of spraying distance at larger flow rate of primary gas. However, flatten degree of molten powder firstly increased and then decreased with the spraying distance at the lower flow rate of primary gas. The microstructure of coatings is denser with larger gas flow rate. Flatten degree increased with plasma power up to 36 kW. Further increase of plasma power results in more round pores appearing in coatings. Effect of spray parameters on the microstructure of wollastonite coatings mainly resulted from the influence on velocity and temperature of the molten droplets.