Effect of Heat Treatment on Characteristics of Plasma Sprayed Hydroxyapatite Coatings

Abstract

Bioactive hydroxyapatite (HA)-coated implants plasma sprayed on Ti6Al4V substrates have been widely used in load-bearing applications because of their biocompatibility and their intimate contact with bone. The improvement of the characteristics of HA coatings is concerned. The purpose of this work was to evaluate corrosion behavior and bond strength of HA coatings after post-deposition heat treatment at 500-700 C. The results indicated that the heat treatment led to recrystallization of amorphous calcium phosphate of as-sprayed HA coatings. The reduction of layer defects associated with plasma-sprayed coatings and the enhancement of the resistance to corrosion took place after heat treatment. Bond strength of the heat-treated coatings was sensitive to the treatment temperature. It is concluded that the heat treatment at 600C for 1 h in air, endowing with increased crystallinity and the reduced defects without significantly reduced bond strength, provided a better corrosion protection than the other two treatment temperatures.

Ceramics and ceramic coatings in orthopaedics

“…The amorphous phase (ACP) dominates the composition in the as-sprayed condition; but controlled crystallization of ACP can be accomplished by post deposition thermal treatments [230]. Porosity is generated within the coating during cooling due to entrapped air, and cracks form due to differential shrinkage.…”

Effect of Crystallization on the Bonding Strength and Failures of Plasma-Sprayed Hydroxyapatite

“…For the present study, the failure mechanism was observed within all the post heating specimens and further clarified for the past studies. 6,28) Figure 7 depicts the overall dependence of bonding strength on heating temperature that can be generalized into two characteristic regions. According to the previous discussion, bonding strength at temperatures lower than 600 C was strongly affected by crystallization, which acted as a main controlling factor.…”

Comparative Study of Microstructures and Material Properties in the Vacuum and Spark Plasma Sintered Ti-Calcium Phosphate Composites

“…The most widely used coating method is plasma spray coating, which severely damages the HAp. [18][19][20][21][22]31) BCP and Ti duplex metal-matrix composites can be viewed as a potential alternative but there are also some unique problems associated with using this approach. At higher temperature, Ti is oxidized and TiO 2 and other oxide products are formed.…”

“…Several methods of coating Ti have been developed including plasma spraying, dip-spin, electro chemical, etc. [18][19][20][21][22][23] However, coating Ti metal surfaces is complex because the bonding strength of the interface of Ti and BCP is very low. Therefore, it is very difficult to uniformly coat an implant with a complex structure using this technique.…”