title: Properties of heat-treated calcium phosphate coatings deposited by high-velocity oxy-fuel (HVOF) spray.
abstract: The influence of crystallization, upon heat treatment, on the properties of high-velocity oxy-fuel (HVOF) sprayed hydroxyapatite (HA) coatings was investigated. The characterization of the HA coating was performed by X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). Differential Scanning Calorimeter (DSC) was employed to determine the crystallization temperature of the amorphous phase in an as-sprayed HA coating. The study demonstrated the effect of crystallization on the coating properties by considering the changes in materials chemistry, crystallinity level, and mechanical performance. Results showed that complete crystallization of the amorphous phase occurred at approximately 700 degrees C and the crystallization temperature was dependent on sample heating rate in the DSC test. The changes of ion groups were detected by FTIR, before and after the phase transformation. The crystallization of the coating after annealing at 750 degrees C resulted in a significant increase of the coatings' adhesive strength and shear strength, which attained maximum values 34 +/- 3 and 14.1 -/+ 0.8 MPa, respectively. Young's modulus increased from 21 +/- 1 to 25 +/- 2 GPa. Microhardness measurements confirmed the changes in coating properties. It is also found that the transformation from the amorphous phase has crystalline HA as the only resultant phase detected by XRD.
authors.affiliation: School of Mechanical & Production Engineering, Nanyang Technological University, Singapore.
authors.forename: H
authors.initials: H
authors.lastname: Li
authors.forename: K A
authors.initials: KA
authors.lastname: Khor
authors.forename: P
authors.initials: P
authors.lastname: Cheang
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry*; D055592:Biophysical Phenomena; D001703:Biophysics; D002130:Calcium Phosphates / Q000494:pharmacology*; D002152:Calorimetry, Differential Scanning; D003460:Crystallization; D018360:Crystallography, X-Ray; D017886:Durapatite / Q000737:chemistry*; D006358:Hot Temperature; D008422:Materials Testing; D017550:Spectroscopy, Fourier Transform Infrared; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature
chemical_list: D001672:Biocompatible Materials; D002130:Calcium Phosphates; C485828:alpha-tricalcium phosphate; C485830:tetracalcium phosphate; C485838:calcium phosphate, monobasic, anhydrous; D017886:Durapatite; C020243:calcium phosphate; C485829:calcium phosphate, dibasic, anhydrous