Hollow cathode plasma nitriding of medical grade Ti6Al4V: A comprehensive study

Abstract

Ti6Al4V used in biomedical applications still has several surface-related problems, such as poor bone compatibility and low wear resistance. In this work, the formation of a protective layer of titanium nitride obtained by plasma treatment in hollow cathode was studied, and the best experimental conditions were verified by a statistical factorial design of experiments. The samples were characterized in terms of their physical and chemical properties, correlating the effects of time (min) and temperature (°C). An achieved ideal condition was further analysed in terms of in vitro cytotoxicity, micro-abrasion, and electrochemical properties. The carried-out assessment has shown that nitrided condition has an improvement in wettability, microhardness, along with TixNy formation and roughness increment, when compared to pristine condition.

Comparative Study of Physicochemical Properties and Biocompatibility (L929 and MG63 Cells) of TiN Coatings Obtained by Plasma Nitriding and Thin Film Deposition

“…This results in a slight enrichment of aluminum below the compound layer in nitrided Ti6Al4V. − The N profile for the TFD sample has a sudden drop, whereas for the HCPN sample, this happens gradually, indicating the deeper incorporation of nitrogen into the alloy in several micrometers . For the HCPN, the N-containing zone is not easily distinguishable by looking at the N profile, because of this smoothly nitrogen-enriched interface. , …”

“…Plasma Nitriding. Plasma nitriding was carried out with the parameters previously described in Fontoura et al (2020), 3 where pressure, temperature, gas inlet, and time were controlled. The chamber was evacuated to a base pressure of 5 × 10 −2 mbar.…”

“…66 For the HCPN, the N-containing zone is not easily distinguishable by looking at the N profile, because of this smoothly nitrogen-enriched interface. 3,67 The depletion of Al taking place on HCPN samples may be a beneficial biological effect, once aluminum has been assumed to be detrimental to a wide range of cells, 22 while also being commonly correlated with neurological diseases in patients who received implants, 23 but it may entail loss of mechanical properties to the alloy. The diffusion events that take place during HCPN processing form a bilayer consisting of δ-TiN, followed by ε-Ti 2 N, arranged in this order because of nitrogen interstitial filling of Ti lattices, either totally or partially.…”

“…1−5 In addition, the residues from shearing and/or wear can release toxic components that cause inflammation and can drastically decrease the lifespan of a prosthesis. 3 Many methods have been used for modifying titanium surfaces in biomedical applications, including deposition of thin films and growth of oxides, carbides, and nitrides, which will improve biocompatibility properties. 6,7 The study of a material's surface is crucial, since its properties can determine biological factors, in particular cell adhesion.…”

“…The surface of a biomaterial plays a complex role in terms of biological interactions with the human body. Therefore, the use of biocompatible materials such as Ti6Al4V without any surface modification has some disadvantages, such as low shear resistance, low wear resistance, low wettability, release of aluminum and vanadium ions that are harmful to the human body, and lack of bioactivity. − In addition, the residues from shearing and/or wear can release toxic components that cause inflammation and can drastically decrease the lifespan of a prosthesis . Many methods have been used for modifying titanium surfaces in biomedical applications, including deposition of thin films and growth of oxides, carbides, and nitrides, which will improve biocompatibility properties. , …”