A Comparative Study of Vacuum and Atmospheric Plasma Sprayed Tantalum Coating for Modification of Titanium Implants

In order to improve the mechanical compatibility and cytocompatibility of titanium implants, tantalum coatings were prepared using plasma spraying technology. Tantalum coatings have been deposited via atmospheric plasama spraying (APS) and vacuum plasma spraying (VPS) methods, and then their morphologies, porosities, bonding strengths and elastic modulous were investigated. In vitro cytocompatibility of the two coatings was evaluated via human bone marrow stromal cells (hBMSCs). The results show that oxidation phenomenon was observed for the APS tantalum coatings, while less oxidation was found in the VPS tantalum coatings. Compared with APS tantalum coatings, the VPS tantalum coatings have a more compact microstructure and less impurity content, resulting in a better bonding with the titanium substrate. VPS tantalum coatings were measured to have a lower elastic modulus and a higher hardness than APS Tantalum coatings. Electrochemical corrosion of the coatings were examined and the VPS tantalum coating showed improved chemical stability. Besides, bone marrow stem cells (BMSCs) adhere to and spread well on the surface of both VPS and APS tantalum coatings without significant difference. The proliferation rate of BMSCs is higher on VPS tantalum coating surface than on APS tantalum coatings. Our results suggest that VPS tantalum coatings are more suitable for the application of surface modification of titanium implant due to their lower elastic modulus and better chemical stability for higher mechanical compatibility and cytocompatibility.