Investigation of coated 316L steel surface employing carbon nanotubes mixed-electrical discharge machining for biomedical applications

This research focuses on the influence of carbon nanotubes on the modified 316L steel surface properties for potential biomedical applications and explores relationships between the process variables and the modified surface properties. Following Taguchi's L9 (3^4) design, carbon nanotube is added in the electro-discharge machining oil to synthesize a biocompatible and hard coating when the machining of 316L steel with a titanium electrode. A few characterization tools such as scanning electron microscope, goniometer, Vickers's hardness, x-ray diffraction (powder X-ray diffraction), atomic force microscope, energy dispersive X-ray, and MTT ((3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, a tetrazole) assay were adopted for performing the modified surface characterizations. A thin coating of 14.65 µm attributing to a small contact angle of 58.97° is found. The lowest surface roughness of 1.63 µm in micron scale and 5.641 nm in nano scale is obtained at a low both current and carbon nanotube amount applications. The morphological results confirm a crack-free, micro and nano porous surface. Compositional analysis ensures carbides, intermetallic and oxides formation on the coated surface. Microhardness of 316L steel is improved by about 86% (269.8 HV). Most importantly, approximately 70% cells are alive, which witnesses the use of carbon nanotube in biocompatible coating formation.