Corrosion and tribocorrosion behavior of Ti–B4C composite intended for orthopaedic implants

Improved Tribocorrosion Behavior Obtained by In-Situ Precipitation of Ti2C in Ti-Nb Alloy

Novel in-situ Ti-based matrix composites (TMCs) were developed through the reactive hot pressing of Ti + NbC powder blends. Due to the chemical reaction that occurred in the solid-state during processing, the produced samples were composed of an Nb-rich β-Ti phase that formed a metallic matrix along with Ti2C as a reinforcing phase. By employing different proportions of Ti:NbC, the phase composition of the alloys was designed to contain different ratios of α-Ti and β-Ti. The present work investigated the corrosion and tribocorrosion behavior of the composites, compared to unreinforced Ti, in a phosphate-buffered solution (PBS) at body temperature. Corrosion tests included potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Tribocorrosion tests were carried out using a ball-on-plate tribometer with sliding performed at open circuit potential (OCP) and under anodic potentiostatic conditions. Results showed that the stabilization of the β phase in the matrix led to a decrease in the hardness. However, the formation of the in-situ reinforcing phase significantly improved the tribocorrosion behavior of the composites due to a load-carrying effect, lowering the corrosion tendency and kinetics under sliding. Furthermore, localized corrosion was not observed at the interface between the reinforcing phase and the matrix.

Tribocorrosion-Resistant Ti40Nb-TiN Composites Having TiO2-Based Nanotubular Surfaces

A novel multifunctional material was developed by hard TiN particle reinforcement addition to a β-type Ti40Nb alloy, followed by surface functionalization, yielding the formation of a nanotubular layer. Corrosion and tribocorrosion behaviors were investigated in a phosphate-buffered saline solution at body temperature. The results revealed that the Ti40Nb-TiN composites presented similar ipass and E(i=0) values together with relatively similar Rox and Cox. However, its tribocorrosion resistance drastically improved (wear volume is almost 15 times lower than an unreinforced alloy) as a consequence of the load-carrying effect given by the reinforcement phases. The corrosion and tribocorrosion behaviors were further improved through surface functionalization as observed by significantly lower ipass and higher Rox values and almost undetectable wear volume loss from tribocorrosion tests due to the formation of a well-adhered anatase-rutile TiO2-based nanotubular layer.

A novel ceramic with low friction and wear toward tribological applications: Boron carbide-silicon carbide

Boron carbide‑silicon carbide ceramic is a novel material as tribological structural components. Compared with traditional tribo-components composed of single-phase boron carbide ceramics or single-phase silicon carbide ceramics, boron carbide‑silicon carbide composite ceramics exhibit better tribological properties under nonlubricated and water lubricated sliding conditions, which is attributed to their in situ formed relief structure on the surface. It is the first time to find that the in situ formed relief structure can enhance the tribological properties of materials. The recent progress on the tribological properties of boron carbide‑silicon carbide ceramics is summarized in this review. Besides, future research directions of boron carbide‑silicon carbide ceramics toward tribological applications are proposed. This review provides some theoretical basis for preparing boron carbide‑silicon carbide ceramics with low friction and wear and points out a new application direction for boron carbide‑silicon carbide ceramics.

Antibacterial application of gentamicin-silk protein coating with smart release function on titanium, polyethylene, and Al2O3 materials

Peri-implant infection after hip and knee arthroplasty is a common and serious complication. Titanium (Ti), polyethylene (PE), and Al₂O₃ materials used as joint prosthesis materials have good biocompatibility and mechanical strength but no antibacterial effect. This study aimed to provide a theoretical basis for the design and manufacture of joint prosthesis materials with antibacterial effect. We applied a coating of gentamicin-silk protein (GS-Silk) on the surface of these materials. We characterized the Ti, PE, and Al₂O₃ materials coated with GS-Silk (experimental group) and performed in vivo and in vitro experiments to test antibacterial activity. Scanning electron microscopy confirmed successful GS-Silk coating, and infrared spectroscopy confirmed successful loading of gentamicin onto the three materials. Nanoscratch test proved that the GS-Silk coating is relatively reliable on the surface of these three materials. The antibacterial effect of the coating in vitro and in vivo was verified by performing bacteriostatic ring test in vitro, bacterial adhesion test, and subendothelial implant infection test. We demonstrated that GS-Silk coating can effectively load gentamicin onto Ti, PE, and Al₂O₃ materials and change the gentamicin release rate with a change in the solution pH to achieve intelligent release. The GS-Silk coating is relatively reliable on the surface of these three materials. Ti, PE, and Al₂O₃ materials coated with GS-Silk have good antibacterial ability, both in vivo and in vitro.

Prediction of tribocorrosion processes in titanium-based dental implants using acoustic emission technique: Initial outcome

The use of dental implants is growing rapidly for the last few decades and Ti-based dental implants are a commonly used prosthetic structure in dentistry. Recently, the combined effect of corrosion and wear, called tribocorrosion, is considered as a major driving process in the early failure of dental implants. However, no previous study has reported the prediction of tribocorrosion processes in advance. Therefore, this study is a novel investigation on how the acoustic emission (AE) technique can predict tribocorrosion processes in commercially-pure titanium (cpTi) and titanium-zirconium (TiZr) alloys. In this study, tribocorrosion tests were performed under potentiostatic conditions and AE detection system associated with it captures AE data. Current evolution and friction coefficient data obtained from the potentiostatic evaluations were compared with AE absolute energy showcased the same data interpretation of tribocorrosion characteristics. Other AE data such as duration, count, and amplitude, matched more closely with other potentiostatic corrosion evaluations and delivered more promising results in the detection of tribocorrosion. Hence, AE can be consider as a tool for predicting tribocorrosion in dental implants. Experimental results also reveal Ti5Zr as one of the most appropriate dental implant materials while exposing Ti10Zr's lower effectiveness to withstand in the simulated oral environment.

Electrochemical Noise Analysis of the Corrosion of Titanium Alloys in NaCl and H2SO4 Solutions

Titanium alloys have been used in aerospace, aeronautic, automotive, biomedical, structural, and other applications because titanium alloys have less density than materials like steel and support higher stress than Al-alloys. However, components made of titanium alloys are exposed to corrosive environments, the most common being industrial and marine atmospheres. This research shows the corrosion behavior of three titanium alloys, specifically Ti-CP2, Ti-6Al-2Sn-4Zr-2Mo, and Ti-6Al-4V with α, near α, and α + β alloys phases. Alloys were exposed in two electrolytes to a 3.5 wt. % H2SO4 and NaCl solution at room temperature, and their electrochemical behavior was studied by electrochemical noise technique (EN) according to ASTM ASTM-G199 standard. EN signal was filtered by three different methods, and the polynomial method was employed to obtain Rn, kurtosis, skew, and the potential spectral density analysis (PSD). The wavelets method was used, from which energy dispersion plots were obtained. The last method was Hilbert–Huang Transform (HHT), where Hilbert Spectra were analyzed. Results indicated that Rn compared with PSD showed that Ti-6Al-2Sn-4Zr-2Mo presented less dissolution in both electrolytes. Statistical methods showed that the passive layer created on Ti alloys’ surfaces is unstable; this condition is notable for Ti-6Al-2Sn-4Zr-2Mo in NaCl solution.

Tribocorrosion behavior of bio-functionalized highly porous titanium

Titanium and its alloys are widely used in orthopedic and dental implants, however, some major clinical concerns such as poor wear resistance, lack of bioactivity, and bone resorption due to stress shielding are yet to be overcome. In order to improve these drawbacks, highly porous Ti samples having functionalized surfaces were developed by powder metallurgy with space holder technique followed by anodic treatment. Tribocorrosion tests were performed in 9g/L NaCl solution using a unidirectional pin-on-disc tribometer under 3N normal load, 1Hz frequency and 4mm track diameter. Open circuit potential (OCP) was measured before, during and after sliding. Worn surfaces investigated by field emission gun scanning electron microscope (FEG-SEM) equipped with energy dispersive X-ray spectroscopy (EDS). Results suggested bio-functionalized highly porous samples presented lower tendency to corrosion under sliding against zirconia pin, mainly due to the load carrying effect given by the hard protruded oxide surfaces formed by the anodic treatment.