| To prepare HA coating on NiTi alloy is able to combine the stability and bioactivity of the ceramic with high strength and the excellent mechanical properties of metallic alloy. Plasma spraying is the most widely method to prepare HA coating due to its simple operation. But plasma spraying has some disadvantages, such as, poor interfacial adherence, low crastallinity, coarse tissue and serve decomposition of HA. Those can result in abscission of coating and dissolution of coating surface in body, which lead to decrease the lifespan of implante .Laser gas nitriding technique (LGN) was used to prepare TiN layer on the NiTi alloy. Then, a HA coating was produced on LGN-NiTi using plasma spraying and pulse laser deposition. The polished substrate and grit blasted were choose to compare. The surface morphology of the coating, phase composition and interfacial structure between the coating and the substrate were investigated. The main research contents and conclusion are as follows:Laser gas nitriding can induce a TiN layer on NiTi alloy with excellent wear and corrosion resistance, and the microhardness of nitriding area was greatly improved.3D-TiN dendrites with truss structure could be prepared on NiTi alloy by laser gas nitriding and selectivity etching. The bonding strength between coating and LGN substrate was improve highly, which was The bonding strength between coating and etched LGN substrate is about 1.8 times and 3.8 times higher than that on grit blasted substrate and polished substrate, respectively. After immersion in Hank's solution for two weeks, the bonding strength between coating and LGN substrate was 26MPa, which is still higher than other substrate.The HA coating prepared by PLD was dense, homogeneous and good interfacial adhesive. TiN dendrite prepared by LGN provided the core of nucleation for HA coating deposition. A lot number of HA particles were deposited on TiN dendrite. The Ca/P ratio of coating on LGN-NiTi was similar to the Ca/P ratio of target. |
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