title: Processing-microstructure-property relations in HVOF sprayed calcium phosphate based bioceramic coatings.
abstract: Hydroxyapatite (HA) based bioceramic coatings were deposited onto titanium alloy substrates using the high velocity oxy-fuel (HVOF) spray technique. This study aimed to reveal the relations among processing parameters, microstructure, and properties of the bioceramic coatings. The processing conditions were altered through changing the starting HA powder size, content of bioinert ceramic additives or composite powder preparation techniques. Coating structure was characterized through scanning electron microscopy (SEM) and transmission electron microscopy (TEM); and the mechanical properties, Young's modulus and fracture toughness, of the coatings were evaluated through indentation techniques. Results demonstrated dominant influence of the melt state of HA powders on the phase composition of resultant coatings, and it was found that the HVOF HA coatings possess competitive mechanical properties. Furthermore, addition of titania or zirconia, as secondary phase in HA, showed promising effect on improving the mechanical properties of the HVOF HA-based coatings. Chemical reactions between HA and titania; and, HA and zirconia during coating deposition were revealed and characterized. Incorporation modes of the additives into HA and their reinforcing mechanisms were elucidated. The relationship among the processing, microstructure, and mechanical properties of the HVOF sprayed bioceramic coatings was summarily examined.
authors.affiliation: School of Mechanical & Production Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore. mkakhor@ntu.edu.sg
authors.forename: K A
authors.initials: KA
authors.lastname: Khor
authors.forename: H
authors.initials: H
authors.lastname: Li
authors.forename: P
authors.initials: P
authors.lastname: Cheang
mesh_terms: D018786:Bone Substitutes / Q000138:chemical synthesis / Q000737:chemistry*; D002130:Calcium Phosphates / Q000138:chemical synthesis / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning; D002516:Ceramics / Q000138:chemical synthesis / Q000737:chemistry*; D020099:Coated Materials, Biocompatible / Q000138:chemical synthesis* / Q000737:chemistry*; D017886:Durapatite / Q000138:chemical synthesis / Q000737:chemistry*; D004548:Elasticity; D006244:Hardness; D008420:Manufactured Materials; D008422:Materials Testing; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D008968:Molecular Conformation; D010316:Particle Size; D011208:Powders; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry; D014961:X-Ray Diffraction; D015019:Yttrium / Q000737:chemistry; D015040:Zirconium / Q000737:chemistry
chemical_list: D018786:Bone Substitutes; D002130:Calcium Phosphates; D020099:Coated Materials, Biocompatible; D011208:Powders; C485828:alpha-tricalcium phosphate; C485830:tetracalcium phosphate; D015019:Yttrium; C485838:calcium phosphate, monobasic, anhydrous; D017886:Durapatite; C020243:calcium phosphate; D015040:Zirconium; D014025:Titanium; C485829:calcium phosphate, dibasic, anhydrous