Corrosion Behavior Of Ti6Al4V Alloy Research Articles

Experimental investigations into corrosion behaviour of DMLS manufactured Ti6Al4V alloy in different biofluids for orthopedic implants

Ti6Al4V alloy is widely used in the biomedical implants industry due to the excellent combination of biocompatibility, mechanical strength & corrosion properties. However, long-time use of Ti6Al4V implants may result in degradation at surge due to corrosive conditions of the human body. In this study, a three-electrode electrochemical cell was used to investigate the corrosion behavior of Ti6Al4V alloy parts manufactured using direct metal laser sintering (DMLS) and conventional cast technique. The corrosion behaviour of Ti6Al4V alloy was investigated in three different biofluids (corrosion media) physiological saline solution (PSS), simulated body fluid (SBF), and phosphate-buffered saline (PBS) using the potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) test. The relevant results showed that the DMLS-produced Ti6Al4V alloy has ~22% higher corrosion resistance than the conventionally cast Ti6Al4V alloy in all three biofluids. The microstructural study revealed that it is due to the fine grains and martensitic microstructure of DMLS-produced samples. Additionally, the DMLS-produced Ti6Al4V alloy in SBF has the lowest corrosion rate of 3.44×10−4 mm per year and exhibits the highest polarization resistance of 3364 Ω.cm2 due to the formation of a stable passive film. Apart from corrosion, the surface characteristics of the corroded samples were also studied using hardness and wettability tests. Additionally, scanning electron microscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction were also performed to understand the reason behind the results obtained. From all these results, it concluded that the corrosion resistance of the cast and DMLS-produced Ti6Al4V alloy in all three biofluids followed the order of PSS <PBS <SBF.

Influence of Component Size on the Corrosion Behavior of Ti6Al4V Alloy Fabricated by Electron Beam Powder Bed Fusion

Influence of Component Size on the Corrosion Behavior of Ti6Al4V Alloy Fabricated by Electron Beam Powder Bed Fusion

Fretting corrosion behavior of Ti6Al4V alloy against zirconia-toughened alumina ceramic in simulated body fluid

The fretting corrosion at the head-neck interface of artificial hip joints is an important reason for the failure of prostheses. The Ti6Al4V alloy-zirconia-toughened alumina (ZTA) ceramic combination has been widely used to make the head and neck of artificial hip joints. In this study, its fretting corrosion behavior in simulated body fluid was studied by electrochemical monitoring, surface morphology characterization, and chemical composition analysis. A running condition fretting map (RCFM) of load and displacement was established, including three regimes, namely partial slip regime (PSR), mixed fretting regime (MFR), and gross slip regime (GSR). The friction dissipation energy increased gradually from the PSR to MFR and GSR. In the PSR, the damage mechanisms were slight abrasive wear and tribocorrosion at the edge of contact area, as well as extremely slight adhesive wear at the center. In the MFR, the damage mechanisms were mainly adhesive wear, abrasive wear, and corrosive wear. In the GSR, the damage mechanism was serious abrasive wear, fatigue wear, and corrosive wear combined with slight adhesive wear. Finally, an ion-concentration map was created, displaying the material-loss transition of different displacements and loads. The material loss increased with the increased displacement, and increased first and then decreased with the increased load.

Laser induced periodic surface structure on titanium alloy and its effect on microstructure refinement and corrosion behavior

Laser induced periodic surface structure (LIPSS) is known to enhance optical properties and adhesion behavior of various materials, but its effect on microstructural evolution and corrosion properties of metallic alloys is not well understood. An effort has been made to study the effect of LIPSS following picosecond laser processing on microstructural evolution and corrosion behavior of Ti6Al4V alloy. The results of electron backscatter diffraction(EBSD) and transmission electron microscope(TEM) indicate that grains at the surface have been refined significantly, while gradient dislocation structure including dislocation cell structure at the top surface and dislocation tangle with high density at the sub-surface has been formed with the increasing depth. The study of polarization suggests that the corrosion resistance increases significantly, which is mainly due to low interface energy of the dislocation cell structure.

Effect of annealing heat treatment on microstructure and corrosion behavior of Ti6Al4V alloy fabricated by multi-laser beam wire-feed additive manufacturing in vacuum environment

Ti6Al4V alloy thin wall was successfully fabricated by multi-laser beam wire-feed additive manufacturing in vacuum environment. The effect of annealing heat treatment (AHT) on microstructure and corrosion behavior of specimens in 3.5 wt% NaCl and 1 mol/L H 2 SO 4 electrolytes was investigated. Results showed that AHT led to the reduction of the non-equilibrium phase α′ and texture weakening. AHT700 was beneficial to achieve crystal refinement while AHT850 had obvious coarsening phenomenon. In addition, AHT could improve the corrosion behavior of the specimens due to the reduction of α′ phase and relief of residual stress. Compared with the specimen of AHT850, the specimen of AHT700 with finer crystal size and obvious texture weakening improved the corrosion resistance more obviously. • Ti6Al4V thin wall is fabricated via multi-laser beam wire-feed additive manufacturing (MLWAM) in vacuum environment. • The effect of annealing heat treatment (AHT) on microstructure and corrosion behavior in 3.5 wt% NaCl and 1 mol/L H2SO4 electrolytes is investigated. • AHT leads to the reduction of α′ phase, texture weakening and relief of residual stress. • AHT is beneficial to improve the corrosion behavior of MLWAM specimens.

Temperature-Dependence Corrosion Behavior of Ti6Al4V in the Presence of HCl

Ti alloys have been widely used in biomedical field due to good compatibility and corrosion resistance. However, corrosion-related failures of implanted Ti devices and prostheses have been regularly reported within the medical literature. The corrosion of Ti alloys has attracted much attention in vivo and in vitro. In the current study, the corrosion behavior of Ti6Al4V alloy was investigated using surface analysis and electrochemical tests. Corrosion of Ti6Al4V in 2 M hydrochloric acid is temperature dependent within the temperature range studied. It has found that the steady state current density at −510 mV vs. SCE (the primary passivation potential at the physiological temperature of 37°C) becomes higher with increasing temperature. The α phase of Ti6Al4V is preferentially dissolved relative to the β phase after potentiostatic measurement at primary passivation potential in 2 M HCl at 37°C. This investigation provides novel and useful information for Ti corrosion-related failures of biomedical implants and prostheses.

Effect of Cr content on microstructure, mechanical properties and corrosion behavior of Ti6Al4V alloy produced by selective laser melting

ABSTRACT In this study, the effect of Cr content on microstructure, mechanical properties and corrosion behaviour of Ti6Al4V alloy produced by selective laser melting (SLM) was investigated. The microstructure exhibited that α' martensite and β phase are obtained in SLM processed Ti6Al4V alloy and Ti6Al4V-Cr system alloys. The increment of Cr content results in the increment of β phase amount. The effect of Cr on the compressive strength and plastic deformation of Ti6Al4V alloy was evaluated by a compression test. The results indicate that the Ti6Al4V+5Cr alloy has a higher compressive strength and superior plastic deformation than that of the SLM processed Ti6Al4V alloy under optimum printing parameters. Meanwhile, the Ti6Al4V+8Cr alloy possesses the best plastic deformation and corrosion resistance. The Ti6Al4V-Cr system alloys, due to the combination of good mechanical properties and corrosion resistant, can be potentially applied in automotive, naval architecture and offshore facility manufacturing.

The influence of process parameters on corrosion behavior of Ti6Al4V alloy processed by selective laser melting

Ti6Al4V alloy exhibits good biocompatibility and has a wide range of applications in the medical fields. Additive manufacturing, especially selective laser melting (SLM), provides a new and effective way for the fabrication of Ti6Al4V alloy biological components. The corrosion resistance of SLM processed Ti6Al4V alloy needs further investigation, which is important for the application of biological components. In this study, Ti6Al4V alloy was fabricated by SLM using different process parameters. Electrochemical measurements including open circuit potential, potentiodynamic polarization, and electrochemical impedance spectroscopy were performed to study the influence of laser scan speed on the corrosion behavior of SLM fabricated Ti6Al4V specimens. The corrosion resistance on different planes of SLM fabricated Ti6Al4V alloy was further characterized. The electrochemical measurements indicated that the corrosion resistance was reduced as the laser scan speed increased. Microstructure analysis suggested that the inferior corrosion resistance under a high laser scan speed was related to the decreased densification behavior. Compared to the XZ-plane, the XY-plane possesses a superior corrosion resistance. The anisotropic corrosion resistance on XY- and XZ-planes of SLM fabricated Ti6Al4V alloys is attributed to the different microstructures on different planes, where more α′ martensite and less β-Ti phase were formed on the XZ-plane than on the XY-plane.

The effect of strain rate on stress corrosion performance of Ti6Al4V alloy produced by additive manufacturing process

Ti6Al4V alloy is considered as a favourable material for additive manufacturing (AM) and in particular for selective laser melting (SLM), due to the inherent difficulties relating to casting and plastic forming of this alloy. However, the significantly increased solidification rate associated with the SLM process results in a modified micro-structure and inherent casting imperfections that can have a detrimental effect on the alloy stress corrosion performance. The main objective of this study was to evaluate the effect of strain rate on stress corrosion behavior of Ti6Al4V alloy produced by SLM, as compared to its wrought alloy (Grade 5) counterpart of the same chemical composition. Micro-structure and phase identification were examined by scanning electron microscopy and X-ray diffraction analysis. General corrosion resistance was evaluated in terms of open circuit potential, potentiodynamic polarization analysis and by impedance spectroscopy, while stress corrosion behavior was examined at various strain rates in a 3.5% NaCl solution at ambient temperature. The results obtained revealed that general corrosion resistance and stress corrosion endurance at slow strain rate, in terms of time to failure and ductility of the SLM alloy, were relatively reduced, as compared to the wrought alloy counterpart. This was mainly due to the formation of a strained martensitic matrix in the form of α' phase and the significant reduction of the β phase in the alloy produced by SLM process.

Effect of Nb addition on mechanical properties and corrosion behavior of Ti6Al4V alloy produced by selective laser melting

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Influence of shallow and deep cryogenic treatment on the corrosion behavior of Ti6Al4V alloy in isotonic solution

AbstractThis study investigated the corrosion behavior of cryogenically treated Ti6Al4V alloys in an isotonic solution. Samples were subjected to shallow or deep cryogenic treatment, and some samples then underwent an aging procedure. They were characterized by microstructural analysis, an open circuit potential test, an electrochemical impedance method, and a potentiodynamic test. The polarization tests demonstrated that the deep cryogenic treatment shifted the corrosion potential to more anodic values compared to the untreated sample. For all treated samples, it was found that the corrosion current densities were lower than those in the untreated sample, and the lowest current densities were registered for the sample subjected to deep cryogenic treatment for 36 hr. The shallow cryogenic treated samples and the sample aged without cryogenic treatment showed semicapacitive loops with poor corrosion impedance compared to the untreated sample, whereas deep cryogenic treatment produced Warburg impedance with diffusion in the solid phase.

Electrochemical behaviour of laser-clad Ti6Al4V with CP Ti in 0.1 M oxalic acid solution

The relationship between the microstructure and corrosion behaviour of Ti6Al4V alloy and laser-clad commercially pure (CP) Ti coating was investigated. The microstructure, phases and properties of the clad layers were investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). Electrochemical measurement techniques including open circuit potential (OCP) and potentiodynamic polarisation were used to evaluate the corrosion behaviour of Ti6Al4V alloy in 0.1 M oxalic acid solution and the results compared to the behaviour of laser-clad CP Ti at varying laser scan speed. Results showed that laser-clad CP Ti at scan speed of 0.4 m/min formed a good cladding layer without defects such as cracks and pores. The phase present in the cladding layer was mostly α′-Ti. The microstructures of the clad layer were needle like acicular/widmanstätten α. An improvement in the microhardness values was also recorded. Although the corrosion potentials of the laser-clad samples were less noble than Ti6Al4V alloy, the polarisation measurement showed that the anodic current density was lower and also increases with increasing laser scanning speed.

Corrosion behaviour of Ti6Al4V alloy in artificial saliva solution with fluoride content and low pH value

The corrosion resistance of the Ti6Al4V alloy in Carter–Brugirard artificial saliva (pH = 5.2), in saliva with sodium fluoride (NaF) addition (pH = 5.2) and in saliva with NaF and lactic acid (pH = 2.0) was evaluated. The open circuit potential of the alloy in all electrolytes was stable after approximately 2 h of immersion. Higher corrosion rate and lower polarization resistance were measured for the alloy immersed in fluoridated saliva, compared to genuine saliva, indicating that the addition of NaF lead to a worse corrosion resistance. In fluoridated and acidified saliva (pH = 2), the Ti6Al4V alloy exhibited the lowest corrosion resistance. The corroded surfaces are much rougher than those non-corroded. A higher roughness was obtained for the alloy immersed in saliva with NaF and low pH, indicating that the corrosion process was more active in this electrolyte. Large precipitates of corrosion products and corrosive sites were found on the samples immersed in all electrolytes.

The influence of TiAlN and enamel coatings on the corrosion behavior of Ti6Al4V alloy in the presence of solid NaCl deposit and water vapor at 450 °C

The corrosion behavior of Ti6Al4V alloy with solid NaCl deposit and water vapor at 450 °C has been investigated. Serious corrosion occurred. In order to improve the corrosion resistance, TiAlN and enamel coatings were prepared, and their effectiveness and corrosion resistance were evaluated. The results indicated that both coatings were effective in protecting the alloy against corrosion induced by NaCl deposit and water vapor at 450 °C. The protection mechanisms of these two coatings were also studied.

Fretting Corrosion Behavior of Ti6Al4V Alloy with Collagen Coated on the Surface

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