Effect of Na2O and ZnO on the microstructure and properties of laser cladding derived CaO-SiO2 ceramic coatings on titanium alloys.

ABSTRACT

To improve the bioactivity of titanium alloy (Ti-6Al-4V), CaO-SiO2 coatings on titanium alloys were fabricated using laser cladding method. The effect of Na2O and ZnO on the microstructure and properties of the prepared coatings was discussed. The microstructure of the CaO-SiO2 coatings consists of cellular grains and cellular dendrites. The mutual diffusion of elements occurs between the coating and substrate. The base CaO-SiO2 coating is composed of different phases including CaTiO3, α-Ca2(SiO4), SiO2, TiO2 and CaO. The formation of CaTiO3 in the ceramic layer was analyzed through thermodynamics. Na2O has little influence on the microstructure, average hardness and wear resistance. When ZnO is added to the precursor, the microstructure turns to cell dendrite, and ZnO and Zn2SiO4 appear in the corresponding coating. The addition of ZnO reduces the average hardness and wear resistance of the ceramic layer. The in vitro soaking in SBF shows that the laser cladding coating has the ability to form an apatite layer.