Formation and Properties of Micro-arc Wollastonite-Calcium Phosphate Coatings on Titanium and Zirconium-Niobium Alloy

摘要

Wollastonite-calcium phosphate (W-CaP) coatings were deposited by the micro-arc oxidation (MAO) method on titanium (Ti) and Zr-1 wt % Nb (Zr-lNb) alloy. The voltage of 150-300 V generated the MAO process with initial current amplitudes of 150-550 A and 100-350 A for Ti and Zr-lNb substrates, respectively. Thin W-CaP coatings with the thickness of 10-11 μm were formed on Ti and Zr-lNb under the low process voltage of 130-150 V. Elongated wollastonite particles with the size in the range of 40-100 μm were observed in such coatings. The structure of the coatings on Ti was mainly in X-ray amorphous state. In this case, X-ray reflexes relating to the crystalline phases of Ti and wollastonite were observed only in XRD patterns of the coatings deposited under 150-200 V. While, the crystalline structure with phases of CaZr_(4()PO_4)6, β-ZrP_2O_7, ZrO_2, and Zr was detected in the coatings on Zr-lNb. FT-IRS, XRD, and SEM data confirmed that the increase of the process voltage up to 300 V leads to the dissociation of the wollastonite.