In-situ synthesis and characterization of calcium phosphate coatings on rapidly solidified zirconia toughened alumina eutectic bioceramics by laser cladding

Rapidly solidified zirconia toughened alumina (ZTA) eutectic bioceramics are promising load-bearing materials that meet the needs for durability and aging resistance for biomedical applications. However, one of the major problems is their poor bioactivity which may lead to aseptic loosening after long-term service. To solve this problem, calcium phosphate (Ca-P) coatings are in-situ synthesized on rapidly solidified ZTA eutectic bioceramics by laser cladding technology with mixed powders of CaHPO₄ ∙ 2H₂O and CaCO₃ after granulation as precursors. X-ray diffraction results show that Ca-P coatings are mainly composed of Ca_0.2Zr_0.8O_1.8, AlPO₄, Ca₄P₂O₉, Ca₃(PO₄)₂ and Ca₂P₂O₇. The amount of calcium phosphates reaches a maximum when using a laser power of 800 W and a scanning rate of 650 mm/min. Cross-sectional morphologies and energy dispersive spectrometer analysis indicate excellent interfacial bonding between the substrate and coating. In vitro tests prove that Ca-P cladded samples can induce apatite with flake-like morphology similar to those on the bioceramic coatings cladded on titatinum alloy precipitation and promote MC3T3-E1 cell proliferation. This work reveals that laser cladding has the potential to improve the biomineralization of solidified ZTA eutectic bioceramics enabling prolonged clinical service life.