Mechanical properties of warm sprayed HATi bio-ceramic composite coatings

To explore a new approach for fabricating the load bearing implants with the combination of bioactivity, bio-compatibility, and mechanical properties, mechanically mixed hydroxyapatite (HA) and titanium (Ti) powders containing 30, 50, and 70 wt% Ti were sprayed onto a 316L stainless steel substrate using a warm spray (WS) process. The microstructures, phase compositions, chemical structures, and mechanical properties of WS HATi composite coatings were comprehensively investigated and compared to those of WS HA coating. Experimental results indicate that the cross-sectional microstructures of WS HATi composite coatings present typical lamellar structures composed of curved stripes formed by well-deformed and oxidized Ti splats and limited deformed HA splats, and are significantly influenced by the Ti content in the original powders. Phase constitutions of the composite coatings mainly consist of HA, Ti, TiO2, and TiO. Chemical structures of HA in the composite coatings deposited using powders with Ti content less than 30% are similar to the structures in the original powder. The microhardness, elastic modulus, and bond strength of the coatings increased from 0.32 +/- 0.15 GPa to 1.41 +/- 0.31 GPa, from 1.37 +/- 0.28 GPa to 23.28 +/- 3.45 GPa, and from 17.3 +/- 2.2 MPa to 34.8 +/- 3.2 MPa, respectively. The abrasive wear weight loss of the coatings on Al2O3 abrasive paper decreased from 2.9 mg to 1 mg, as the addition of Ti particles in original powders increased from 0 to 70%.