Study On Microstructure And Properties Of Bioceramic Coatings By Laser Cladding On The Surface Of Titanium Alloy

Preparing bioceramic coatings on Titanium alloy substrate can combine the stabilityand good biological activity of bioceramic with high-strength and good toughness of metal.For their similar composition with natural bone which can improve biological activity ofhydroxyapatite （HA） effectively and have lower solubility, the emerging Si-substitutedhydroxyapatite （Si-HA） and Fluoridated hydroxyapatite （FHA） have been chosen as themain alternative materials of the biological activity bone for clinical trials. Laser claddingis a promising method in producing bioceramic coatings because it could acquire a seriousof biological coatings with special performance such as higher interfacial bonding strengthand adjustable coating thickness. This paper uses HA+CaF₂and HA+SiO₂as rawmaterials, producing bioceramic coatings of FHA and Si-HA by laser cladding, toaccumulate data for artificial implant materials of further research on clinical trials. Thesehave been researched as follows:Firstly, the composition and the proportion of the coating powder were optimizedand laser cladding experiment was made in different technic condition. The optimal lasertechnics parameters under CO₂laser experimental conditions were as follows: P=0.7kW,V=200mm/min, D=15mm×2mm; the optimal laser technics parameters under fiber laserexperimental conditions were as follows: P=1.0kW, V=720mm/min, φ=6mm （P: laseroutput power; V: laser scanning speed; D: laser beam size; φ: laser spot diameter）.Secondly, the microstructure and mechanical properties of laser cladded compositecoatings were investigated. The results indicated that the coatings were metallurgicallybonded to the titanium alloy substrate, which prepared under the optimized processingparameters. The contents of most elements distribute gradiently from coating surface tosubstrate. The laser-cladded coatings contained such matrix phase as TiO₂, CaO andbioactive phases as Ca₃（PO₄）₂, CaTiO₃, Ca₄Ti₃O₁₀, Ca₂SiO₄, Ca₃（PO₄）₂xH₂O andCa₅（PO₄）₃F, etc. The composite coating surface presented multiform morphologies such asflocculent, short rod accumulation like, honeycomb, lamellar and coralline-like, etc. Themicrohardness of the coatings increased prominently compared with the matrix by lasercladding. Finally, the biological activity of bioceramic coatings was studied preliminarily bysimulated body fluid （SBF） test. It indicated that the composite coatings had somebiological activity for there was calcium phosphate deposited on the coating surface. Theceramic coatings with the circular spot scanning had better deposition of biologicalactivity phase compared with the broad-beam. It associated with difference in energydistribution and acting time between the CO₂laser and fiber laser.