Surface alteration of biomedical alloys by electrical discharge treatment for enhancing the electrochemical corrosion, tribological and biological performances

Abstract

In the current research, the electrical discharge treated (EDT) biomedical alloys substrates such as cobalt-chromium (F90), stainless steel (316L) and titanium (Beta type) have been investigated for their in-vitro biocompatibility, corrosion resistance and tribological performance. The alloys substrates were machined by copper tungsten tool electrode in a deionized water tank at 10A current, 200μs pulse on-time, 60μs pulse off-time. To examine the corrosion rate of the substrates, the electrochemical potentiodynamic test was executed in which Tafel slopes were designed. Further, cytocompatibility and hemocompatibility tests were performed on the substrates to study the in-vitro biocompatibility. Moreover, the tribological characteristics such as wear rate and coefficient of friction were investigated on a pin-on-disc tribometer. The results revealed that the modification of the substrate was perceived to be effective in increasing the corrosion resistance of cobalt-chromium alloy, titanium alloy and stainless steel alloy by 86.39%, 62.15% and 56.21%, respectively in comparison to the unmachined substrates. Similarly, the tribological results exhibited that the altered substrates have improved friction-reducing characteristics and higher wear-resistance. The cytocompatibility and hemocompatibility outcomes validating the higher %cell viability and low RBC-lysis on treated substrates. The existence of titanium carbide (TiC), niobium carbide (NbC) and tungsten carbide (WC) phases on EDT substrates were detected from X-ray diffraction examination favors the synthesis of the hard and wear-resistant surface. Although, the formation of oxides, nitrides and phosphides during the EDT process lead to developing bio-inert surfaces and also ameliorates the corrosion resistance of the alloy. However, the F-90 cobalt-chromium alloy substrate showed improved corrosion, wear and biocompatibility responses as compared to titanium and stainless steel alloy. Therefore, the metallurgical alteration during EDT and the inherent bulk properties of base alloy contributed towards its biocompatibility and surface properties. These results promote the EDT biomedical alloys in bulk in the biomedical field.