Surface modification of nitinol by using electrical discharge coatings in deionized water

Abstract

Nitinol, also known as nickel-titanium shape memory alloy, has a high potential in medical implantation due to its unique mechanical properties, shape memory effect, and low modulus of elasticity which close to bone’s modulus. However, high composition of nickel element in this alloy is harmful whenever the element is released into human body that can induce inflammation and allergic reactions. The objective of this study is to develop a deposition layer of titanium oxide on nitinol surface through the study of electrical discharge coatings (EDC) parameters effects. In particular, deionized water and pure titanium rod were as the dielectric fluids and electrodes, respectively, during the EDC process. Variation settings of polarity, gap voltage and erosion depth were employed in this study. Experimental results examined the coating thickness and surface roughness through full factorial design with ANOVA analysis. It was determined that the polarity gave the highest significant effect on the deposition thickness. Meanwhile, the interaction between polarity and gap voltage was exhibited significant effect to the surface roughness. In additional, reverse polarity and low gap voltage were preferred in EDC process to provide good surface roughness and higher uniformity of the material deposition.