Structure of TiN/hydroxyapatite multilayers deposited on surface of NiTi shape memory alloy

Abstract

In order to improve a corrosion resistance and biocompatibility of NiTi shape memory alloys, the surface of the NiTi alloy was covered by protective layers. The paper presents results of the layers composed of titanium nitride and hydroxyapatite (HAp). The TiN layers were deposited using the glow discharge technique and then the bioactive hydroxyapatite layer was formed from simulated body fluids solution. The results of the structure studies and microscopic observations confirmed that on the surface of the NiTi alloy a thin titanium nitride layer 35-50 nm thick (depending on the glow discharge technique parameters) was obtained. The structure of the deposited layers was studied by means of the X-ray diffraction technique. Also, mechanical parameters of obtained layers were characterized using nanoindentation. On the top of the titanium nitride, a layer consisted of hydroxyapatite and NaCl was formed. Applied parameters of deposition process did not lead to decomposition of the NiTi parent phase (B2) to the equilibrium ones.