Microstructure and wear resistance of double-layer TiN/PSZ coatings from alkoxide solutions by H2O-containing thermal plasma CVD

Double-layer TiN/PSZ coatings approximately 2 µm thick were deposited on Si wafers and WC–Co cutting tools from Ti-, Zr-, and Y-alkoxide solutions by Ar/H2/N2 thermal plasma chemical vapor deposition with water functioning as an oxidant. A PSZ layer was deposited on TiN films upon oxidation of Zr- and Y-alkoxides by H2O using five-step-wise and pulse-type supply methods. The double-layer coatings were characterized by X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), in-depth glow discharge optical emission spectrometry, and cutting tests. Two H2O supply methods, two-stage pulse and five-step-wise supply methods, were shown to be suitable for the formation of the double-layer coatings by SEM and TEM observation of surface and cross-sectional microstructures. Cutting tests for the double-layer coatings deposited on WC–Co cutting tools prepared by the above two H2O supply methods were carried out to evaluate their wear resistance.