Leonardo Contri Campanelli

This study evaluates electropolishing as a surface preparation method for the Ti-6Al-4V ELI alloy for implant applications, aiming to reduce surface roughness and improve wettability behavior. Alloy samples were subjected to electropolishing in a solution of acetic acid, perchloric acid, and glycerol, under different voltages (13–18 V) and times (5, 10, and 15 min). The surfaces were characterized by scanning electron microscopy, profilometry, and contact angle measurements. Higher voltages and longer anodizing times favored roughness reduction. The average Ra, calculated from samples analyzed in triplicate, was 70.207 nm, with a standard deviation of 19.260 nm, obtained under the condition of 18 V for 15 minutes. The largest contact angles, 112.62° and 110.74°, were observed at 14 V for 10 and 15 minutes, respectively, suggesting that factors beyond surface topography influence wettability. It was concluded that electropolishing is an effective method for preparing the surface of Ti-6Al-4V ELI, with potential for implant applications, and that the parameters should be adjusted according to the desired performance (surface finish, hydrophobicity, or hydrophilicity).

The high-strength low-alloy (HSLA) steels present a challenge in balancing mechanical performance, cost and formability. The HSLA steel design involves adjusting the carbon (C) content and incorporating microalloying elements such as niobium (Nb), vanadium (V), titanium (Ti), which contribute through precipitation hardening, solid solution strengthening, and grain refinement. Nb is the primary microalloying element; it enhances tensile properties by refining the austenitic grain size during hot rolling, increasing hardness, and providing strength, usually, via Nb(C,N) or NbC precipitation. The morphology, size, and distribution of these precipitates critically impact the steel’s behavior. Thermo-Mechanical Control Processing (TMCP) further enhances material properties through Nb addition. However, the effectiveness of Nb in the continuous rolling of long products requires thorough evaluation. This study addresses this issue by quantifying and correlating the effect of Nb under conditions different from those of TMCP, evaluating its effect on the grain size, tensile properties, impact energy absorption, and hardness of AISI 4320 steel following conventional rolling. The results indicate that Nb addition between 200 and 500 ppm improves the yield strength by approximately 10%, while the ultimate tensile strength increases by about 6%. The particle size distribution of the precipitates reveals unusual findings regarding the grain refinement capability of Nb.

Tecnol. Metal. Mater. Min., vol.22, e3204, 2025

Titanium and its alloys are the most commonly used materials for biomedical applications such as implants. The Ti-6Al-4V ELI (Extra Low Interstitial) alloy is particularly desired for its excellent mechanical performance and remarkable biocompatibility. However, infection is a limiting factor after implantation, making it necessary to adopt surface treatment to minimize this process. Bacterial adhesion to the substrate is strongly influenced by surface roughness and wettability. Therefore, the present study aims to evaluate these parameters after dry electropolishing of the Ti-6Al-4V ELI alloy. The Ti-6Al-4V ELI samples were sectioned with Ø = 14 mm and 3 mm thick, followed by sanding with silicon carbide #600, #1200 and #1600. Subsequently, they were sent for dry electropolishing for 30 min with a voltage potential of 13 to 18 V and characterized. Data were processed statistically using ANOVA. The Ra roughness values were statistically significant: 143±24 nm for 17 V compared to 193±18 nm for the control. The wettability test confirmed that all surfaces obtained are considered hydrophilic, favorable for lower bacterial adhesion, with 16 V being the best condition. Contact angle was found to be 77±6° for 16 V and 59±4° for the control. Dry electropolishing is essential for surface enhancement and biomedical applications.

This study presents a detailed analysis of the feasibility of Ti-15Mo alloy for coronary stents by independently applying the TOPSIS and RADAR multi-parameter selection methods independently and comparing the results obtained. The research focused on evaluating β-metastable titanium alloys for use in coronary stents, employing the TOPSIS and RADAR methods for a comprehensive and independent analysis. The independent application of these methods enabled for a robust and detailed comparison between different candidate materials, considering crucial criteria such as mechanical strength, biocompatibility, and cost-effectiveness. The results showed that the Ti-15Mo alloy excelled in terms of safety and mechanical performance in both methodologies, offering a combination of mechanical properties and biological compatibility suitable for this application. Compared to 316L stainless steel and Co-Cr L605, Ti-15Mo consistently outperformed across multiple criteria. This study positions Ti-15Mo as a promising candidate for coronary stents and emphasizes the effectiveness of combining TOPSIS and RADAR methodologies for comprehensive material selection in biomedical applications. The research underscores the importance of detailed and methodological evaluation to optimize the performance and safety of advanced biomedical devices.

Modifying the surface of titanium alloys with a laser considerably increases the specific area, which has beneficial implications for the osseointegration process. In this study, Yb:YAG laser was used to modify the surface of the commercial β-type Ti-15Mo alloy. The process parameters used were based on a suitable osseointegration condition for this treatment. The effect of such modification on the fatigue performance of the alloy was analyzed. To assess the impact of surface modification on the alloy’s fatigue performance, axial fatigue tests were conducted on specimens with both polished and laser-modified surfaces (R = 0.1). Fatigue strength was evaluated using a staircase method, where specimens were subjected to varying maximum stress levels to determine the fatigue limit after 5x10⁶ cycles. The results showed that the laser-modified surface presented cavities and roughness values such that the effect on fatigue was highly detrimental. A reduction of around 75% in the fatigue limit (maximum stress) was obtained, indicating that modifying the Ti-15Mo alloy with laser for medical purposes may require integrated biological-mechanical development.