AVS 49th International Symposium
    Plasma Science Tuesday Sessions
       Session PS-TuP

Paper PS-TuP27
Bond Strength Improvement of Plasma Sprayed Hydroxyapateite/Titanium Composite Coatings on Titanium: Partial Nitriding of Titanium Deposits by RF Thermal Plasma

Tuesday, November 5, 2002, 5:30 pm, Room Exhibit Hall B2

Session: Plasma Applications
Presenter: M. Inagaki, National Institute of Advanced Industrial Science and Technology (AIST), Japan
Authors: M. Inagaki, National Institute of Advanced Industrial Science and Technology (AIST), Japan
Y. Yokogawa, National Institute of Advanced Industrial Science and Technology (AIST), Japan
T. Kameyama, National Institute of Advanced Industrial Science and Technology (AIST), Japan
Correspondent: Click to Email
Plasma sprayed hydroxyapatite (HA) coating on titanium alloy substrates has been used for medical application to promote the osteoconductivity of implanted materials. For practical application, such as artificial joint, HA coatings with excellent adhesion to the substrate have been strongly demanded to ensure long-time fixation. However, due to the large difference in thermal expansion coefficients between coated ceramics and metal substrates, residual stress arises at the metal/ceramics interface. Such residual stress often causes cracks and reduces the bond strength of coatings. Recently, we have developed a radio frequency (RF)-TPS method that allows us to obtain strong adhesion between HA coatings and titanium (Ti) substrates by employing a HA/Ti composite coating. Here, we briefly describe a promising method to improve the adhesiveness of HA/Ti composite coatings by RF-TPS method. HA/Ti composite coatings were deposited on titanium substrates by a RF-TPS method with RF input powers of 10-30 kW. Partial nitriding of Ti deposits conducted by plasma-enhanced reaction during plasma spraying of HA/Ti composite coatings. The ratio of HA and Ti powders supplied into the plasma was precisely controlled by two microfeeders so as to change the composition from Ti-rich to HA-rich toward the upper layer of the coatings. The bond (tensile) strength of HA/Ti composite coatings was 40-65 MPa. XRD patterns of Ti coatings without HA showed that titanium nitride was formed at the surface of titanium deposits sprayed with N@sub 2@ plasma gas. Scanning electron microscopic observation showed an acicular texture on the Ti deposits prepared with N@sub 2@ added plasma gas.