Deposition of highly adhesive ZrO2 coating on Ti and CoCrMo implant materials using plasma spraying

ZrO2 (4%CeO2) and ZrO2 (3%Y2O3) coatings were deposited on titanium (Ti) and CoCrMo implants using plasma spraying and the adhesive, morphological and structural properties of the plasma-sprayed coatings were evaluated. Characterization of these coatings was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), surface roughness, hardness, and adhesive strength. XRD patterns showed that both the coatings appeared to be primitive tetragonal phase. SEM observations showed that both the ZrO2 coatings appeared to be rough, porous and melted. The cross-section surface morphology of the coatings, coating–substrate interfaces and substrates without acid etching was very dense and smooth. After acid etching, as compared to the dense ZrO2 coating–CoCrMo substrate interfaces, the thin gaps appeared within the ZrO2 coating–Ti substrate interfaces. It is suggested that plasma spraying probably formed an amorphous Ti layer in the coating–Ti substrate interface that can be removed by acid etching. The average surface roughness of ZrO2 (3%Y2O3) and ZrO2 (4%CeO2) coatings was correlated to the starting powder size and substrates. No significant difference between the hardness of all coatings and substrates was observed. The adhesive strengths of ZrO2 (4%CeO2) coating to Ti and CoCrMo substrates were higher than 68 MPa and significantly greater than that of ZrO2 (3%Y2O3) coatings.