Characterization of plasma sprayed wollastonite powder and coatings

Spheroidized wollastonite powder was prepared by plasma spraying natural wollastonite TC powder into water. The natural and spheroidized wollastonite powders were deposited onto Ti–6Al–4V substrates using an atmospheric plasma spraying system. The phase composition and microstructure of the powders and coatings were examined using scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The spheroidized powder prepared by plasma spray presented a sphere-like morphology and was composed of crystalline wollastonite and a little glassy phase. The SEM view of the surface and the cross-section of the coatings revealed that the coating produced with the spheroidized wollastonite powder possesses a denser structure with fewer microcracks and pores than the coating generated from the natural powder. The tensile adhesion test (TAT) specified by ASTM C-633 was used to measure the tensile bonding strength of the coating. The results indicated that the coating produced with the spheroidized powder is superior to the coating prepared from the natural powder.