Study on surface properties of nanosecond laser textured plasma nitrided titanium alloy

Abstract

To optimize the surface properties of biotitanium alloy, a nitride layer was prepared on its surface by plasma nitriding process, and then a nanosecond laser was used to prepare microtextures on the surface of plasma nitrided (PN) titanium alloy to optimize its surface wetting properties and biocompatibility. The three-dimensional morphology of laser ablation grooves was observed, and the effects of laser parameters on the width and depth of the ablation grooves. The ablation regulation was investigated to select the optimal parameters for the preparation of microtextures (stripes and grids). It was found that the material removal rate was positively correlated with the laser pulse overlap rate, and the laser overlap rate decreased with the increasing of ablation speed and increased with the increasing of laser repetition frequency. Diffraction peaks of Ti-N-O non-integrable compounds appeared on the ablated surface of microtextured samples. The regular ablation textures appeared on the surface of textured samples, and granular melt products appeared at the edges of the textures. The wettability of microtextured samples was improved, which was beneficial to improve the biocompatibility of PN titanium alloy. Due to the overlapping of scan paths, the ablation morphology of textured samples with scan spacing smaller than the spot diameter was irregular and the depth of ablative groove was smaller, which has better wettability. The electrochemical corrosion tests showed that the corrosion resistance of the samples with 0.05 mm scanning spacing was better than that of the samples with 0.02 mm scanning spacing. In addition, after 30 days of immersion corrosion, only a few corrosion products appeared on the surface of all the textured samples, and no corrosion cracks and holes appeared, so the laser textured PN titanium alloy has better corrosion resistance.