Superior Corrosion Resistance Research Articles

Corrosion behavior of TiZrNbC coatings on TA1 substrates in simulated PEM water electrolysis

A TiZrNbC coating was deposited on the TA1 substrate by magnetron sputtering technology, and the corrosion behaviors of the TiZrNbC coating in a simulated proton exchange membrane water electrolysis (PEMWE) environment under fluctuating potentials were investigated. The microstructures and elemental distributions of the coating were characterized by SEM and EDS. The PEMWE environment was simulated using a dilute H2SO4 solution with pH = 3 and a 5 ppm of fluoride (F-) ions addition, and polarization tests were conducted under the potentials with constant, square and triangular waveforms. The corrosion resistances of the TiZrNbC-coated and bare TA1 substrates were characterized by potentiodynamic polarization, electrochemical impedance spectroscopy and interfacial contact resistance tests. Compared to the bare TA1 substrates, the TiZrNbC-coated TA1 substrates exhibited lower corrosion current densities, higher polarization resistances and lower contact resistances, demonstrating a superior corrosion resistance.

Microstructural evolution and corrosion behavior of non-isothermally heat treated hypoeutectic Al-Si-Cu alloy

In the present work the effect of non-isothermal heat treatments on the microstructure and corrosion resistance of a hypoeutectic Al-Si-Cu die-cast alloy was studied. The microstructural aspects were examined by confocal laser scanning microscopy and scanning electron microscopy. The corrosion behavior was studied by potentiodynamic polarization tests. In the as-cast condition, the microstructure consisted of needle-like Si particles and Fe-rich intermetallics, besides the Al matrix. The non-isothermal treatments promoted spheroidization of Si particles, decreasing its volume fraction. The corrosion resistance was affected by concentration of the Si particles. The corrosion mechanism is discussed based on the microstructural evolution of the Al-Si-Cu alloy. The main influencing factor was the volume fraction of Si particles. The non-isothermally treated samples exhibited lower corrosion current density than the as-cast alloy, showing superior corrosion resistance.

Microstructure, Hardness and High-Temperature Corrosion Behaviors in Sulfur-Containing Environment of Laser Cladding Y2O3/IN625 Composite Coating

Water-cooled wall tubes are susceptible to high-temperature corrosion during service. Applying high-performance coatings via laser cladding on the tube surfaces can significantly enhance corrosion resistance and extend the service life of the tubes, providing substantial economic advantages. This paper prepared Y2O3/IN625 composite coating by means of high-speed laser cladding. Furthermore, the effects of Y2O3 addition on the microstructure evolution, hardness, as well as the high-temperature corrosion behaviors have been systematically investigated. The results show that Y2O3 addition can effectively refine the microstructure of the Inconel 625 coating, but the phase composition has little change. The coating’s hardness can also be improved by about 7.7%, reaching about 300 HV. Compared to Inconel 625 coating, the Y2O3-added composited coating shows superior high-temperature corrosion resistance, with the corrosion mass gain decreased by about 36.6%. The denser and tightly bonded Cr-rich oxides layer can be formed adjacent to the coating surface, which plays a predominant role in improving the coating corrosion resistance.

Durability Properties of Steel Textiles and Bonding Properties at the Interface of Steel Textiles with Reinforced Mortar-Reinforced Concrete Systems.

Aging and deterioration of building structures have been persistent concerns in the field of engineering. To address these challenges while supporting modern green and sustainable development goals, this study introduces an innovative reinforcement system that employs steel textiles as the primary reinforcing material. The steel textiles were engineered by optimizing the compatibility between steel fibers and a hot melt adhesive (HMA). These textiles were then used to reinforce concrete structures, creating a steel textile-reinforced mortar (STRM)-reinforced concrete system. The study also examined the durability of the steel textiles and the interfacial bonding performance within the STRM-reinforced concrete system. The results showed that the compatibility between steel fibers and ethylene vinyl acetate copolymer (HMA-2) is better, and the steel textiles prepared with it have superior hydrothermal and corrosion resistance. After the system had been maintained for 28 days, the overall flexural strength of the STRM-reinforced concrete system was increased by 100.03%, the interfacial shear load by 49.54%, the interfacial shear stiffness by 61.2%, and the positive tensile bond performance by 26.1%. This proves that STRM has a good reinforcement effect on the concrete reinforcement system.

Investigating the Corrosion Inhibition Performance of a Novel Coconut Oil-Based Poly(urethane-urea) Hybrid Coating on Carbon Steel in 3.5% NaCl Solution

Polyurethane has been used for years as an anti-corrosion coating due to its intrinsic hydrophobic properties. However, its hydrophobicity is not enough to inhibit the permeation of corrosive agents; thus, incorporating it with polyurea would further enhance its hydrophobic properties. In this study, coconut oil, a saturated, low molecular weight vegetable oil, was employed as an eco-friendly precursor for synthesizing a novel poly(urethane-urea)- based hybrid coating. The synthesis process involved the utilization of a coconut oil-based polyol blend, triethanolamine (TEA) as an amine source, and hexamethylene diisocyanate (HDI). The resulting hybrid coating on carbon steel demonstrated remarkable anticorrosion performance in a 3.5 wt. % NaCl solution, owing to the intrinsic hydrophobic characteristics of coconut oil and polyurea. Significant corrosion rate reduction was observed with increasing amine content, accompanied by an enhancement in mechanical properties. Notably, an amine loading of 4% consistently exhibited superior corrosion resistance and mechanical performance in the hybrid coating. Chemical structural analysis revealed a hydrogen-bonding network in polyurea coatings, reducing porosity, enhancing barrier properties, and improving mechanical characteristics, highlighting its potential for sustainable corrosion protection.

Investigation on corrosion behaviour of metal oxide nanoparticles reinforced magnesium composites by salt spray and immersion corrosion test methods

ABSTRACT This study explores the increasing utilisation of lightweight materials, particularly magnesium (Mg) alloy, in sectors such as automobile, aerospace, and marine due to its notable advantages such as high strength-to-weight ratio, good castability, and excellent damping capacity. Despite these merits, Mg alloy faces challenges, notably in wear and corrosion resistance. The research focuses on enhancing the corrosion resistance of Mg alloy by incorporating Zinc Oxide (ZnO), Manganese Oxide (MnO), and Titanium Oxide (TiO2) nanoparticles. The alloy AZ91D and three nanocomposites, namely AZ91D + 1% ZnO, AZ91D + 1% MnO, and AZ91D + 1% TiO2, were manufactured using a stir squeeze casting technique combined with an ultrasonication process. To confirm the even distribution of reinforcement particles, Optical Microscope (OM), Scanning Electron Microscope (SEM) and High-Resolution Scanning Electron Microscope (HR-SEM) were employed. X-ray Diffraction (XRD) analysis revealed the presence of matrix and reinforcement material with intermetallic precipitates around the grain boundaries. Corrosion properties were assessed following ASTM standards and utilising a 3.5% NaCl concentration. The study found that AZ91D + 1% TiO2 nanocomposites exhibited superior corrosion resistance compared to the AZ91D alloy, showing a remarkable 77.78% and 69.89% improvement in corrosion behaviour under salt spray and immersion environments, respectively, after 48 hours.

Concept and Experimental Validation of Using Titanium Alloy Bars (TiABs) as Flexural Reinforcing in Concrete Beams

The research focuses on the use of Titanium Alloy Bars (TiABs) in concrete cap beams. TiABs offer good ductility, high strength, lightweight, superior corrosion resistance, lower overstrength, and better fatigue performance. TiABs have recently been used in several existing bridges in Oregon and Texas in the United States to increase shear and flexural capacities of concrete beams. While TiABs have been implemented in retrofitting of existing bridges in the United States, their application in new structures have not been tested and compared against conventional steel rebars. The research in this paper proposes concept for an innovative cap beam reinforced with longitudinal TiABs. The cap beam integrates both structural performance and durability. Flexural and shear design procedures for the cap beam in accordance with the AASHTO LRFD Design are discussed. To investigate structural performance, a large-scale cap beam reinforced with longitudinal grade 5 titanium alloy (Ti-6Al-4V) is tested under three-point bending test protocol. The results are compared against a benchmark cast-in-place beam with normal rebars under the same testing arrangement and loading protocol.

Enhanced steam thermal cycle resistance of Yb2Si2O7 environmental barrier coatings via Al modification

SiC-based ceramic matrix composites are susceptible to performance losses in steam environments, necessitating the use of environmental barrier coatings for their protection. The high Si activity of Yb2Si2O7 material may induce the emergence of Si(OH)4 in steam environments, resulting in the development of a pore structure within Yb2Si2O7. This pore structure weakens the service life of the coating, highlighting the importance of enhancing the steam corrosion resistance of environmental barrier coatings as a key factor in improving their overall longevity. In the present study, we employed Al modification technique to improve the steam corrosion resistance of Yb2Si2O7 coatings. The results indicated that Al-modified Yb2Si2O7 coatings exhibited superior steam thermal cycle corrosion resistance compared to the non-modified Yb2Si2O7 coatings after testing performed at 1523 K for 1000 h (10 h per cycle). This improvement was attributed to the presence of Yb3Al5O12 and Al2O3 composite phases within the Al-modified Yb2Si2O7 coatings, which exhibited low steam activity and effective steam corrosion resistance. Moreover, Al-modified Yb2Si2O7 coatings obtained the dual excellent performance of improving the steam corrosion resistance of Yb2Si2O7 coating and not weakening the thermal cycle ability, providing a guarantee for the longer life of Yb2Si2O7 coating.

Enhanced Corrosion Protection of Printed Circuit Board Electronics using Cold Atmospheric Plasma-Assisted SiOx Coatings.

The miniaturization and widespread deployment of electronic devices across diverse environments have heightened their vulnerability to corrosion, particularly affecting copper traces within printed circuit boards (PCBs). Conventional protective methods, such as conformal coatings, face challenges including the necessity for a critical thickness to ensure effective barrier properties and the requirement for multiple steps of drying and curing to eliminate solvent entrapment within polymer coatings. This study investigates cold atmospheric plasma (CAP) as an innovative technique for directly depositing ultrathin silicon oxide (SiOx) coatings onto copper surfaces to enhance corrosion protection in PCBs. A systematic investigation was undertaken to examine how the scanning speed of the CAP deposition head impacts the film quality and corrosion resistance. The research aims to determine the optimal scanning speed of the CAP deposition head that achieves complete surface coverage while promoting effective cross-linking and minimizing unreacted precursor entrapment, resulting in superior electrical barrier and mechanical properties. The CAP coating process demonstrated the capability of depositing SiOx onto copper surfaces at various thicknesses ranging from 70 to 1110 nm through a single deposition process by simply adjusting the scanning speed of the plasma head (5-75 mm/s). Evaluation of material corrosion barrier characteristics revealed that scanning speeds of 45 mm/s of the plasma deposition head provided an effective coating thickness of 140 nm, exhibiting superior corrosion resistance (30-fold) compared to that of uncoated copper. As a proof of concept, the efficacy of CAP-deposited SiOx coatings was demonstrated by protecting an LED circuit in saltwater and by coating printed circuits for potential agricultural sensor applications. These CAP-deposited coatings offer performance comparable to or superior to traditional conformal polymeric coatings. This research presents CAP-deposited SiOx coatings as a promising approach for effective and scalable corrosion protection in miniaturized electronics.

Zr-based conversion film fabricated on cold rolled steel by separately providing zirconium and fluorine ions: Performance and mechanism study

Controlling the concentrations of Zr4+ and F− in traditional Zirconium (Zr)-based film-formation solution is challenging due to their dependence on the hydrolytic equilibrium of H2ZrF6. In this study, Zr-based films were prepared on cold rolled steel surface through the film-formation solution prepared by mixing Zr(NO3)4 and different amount of HF. The electrochemical results demonstrated that the Zr-based film prepared by Zr(NO3)4 and HF exhibited superior corrosion resistance compared to H2ZrF6. Under optimal film formation conditions, the protective efficiency of the prepared film reached 74.4 % which was higher than that of film fabricated in H2ZrF6. The electrochemical results concurrently demonstrated the self-reinforcing anti-corrosion performance of the prepared films. Scanning electron microscopy revealed that the Zr film, prepared in Zr(NO3)4 and HF, exhibited excellent corrosion resistance attributed to its high film density. The X-ray photoelectron spectroscopy and energy dispersive spectroscopic results indicated the presence of a fluoride layer on the surface of the Zr film. The F− ions can chelate with the corrosion products and selectively deposit onto the damaged areas of the film, thereby effectively contributing to the repair of the film layer. The results of density functional theory calculations demonstrated that Zr4+ readily forms Zr(OH)4 rather than ZrF62−. The present study offers an enhanced approach for regulating the properties of films prepared via H2ZrF6 by separately providing zirconium and fluorine ions.

Characterization of Nano-kaolin and its enhancement of the mechanical and corrosion resistance of epoxy coatings

This study compares the effects of varying concentrations of nano-kaolin and titanium dioxide on the mechanical and corrosion resistance of epoxy coatings. Characterization techniques such as TEM, XRD, Raman, FTIR, XPS, and AFM revealed surface features of nano-kaolin: the particle size reached the nanoscale, the XRD diffraction peak at 2θ = 25.3° disappeared, Raman peaks broadened with decreased intensity, and a blue shift occurred in the FTIR spectra for various functional groups. Compared to pure epoxy coatings, the composite epoxy coating with 10 wt% nano-kaolin showed an 83.87 % increase in adhesion, an 81.82 % improvement in impact resistance, and a 61.42 % reduction in friction coefficient; while a 20 wt% titanium dioxide composite coating showed a 74.19 % increase in adhesion, a 75.76 % improvement in impact resistance, and a 46.9 % reduction in friction coefficient. Electrochemical tests indicated that a composite coating with 10 wt% nano-kaolin, after soaking in 3.5 wt% NaCl solution for 960 hours, achieved a corrosion efficiency of 98.87 % and an impedance modulus of 108.8Ω.cm2, which was three orders of magnitude higher than that of pure epoxy resin, increasing corrosion resistance by 57.14 %; whereas a 20 wt% titanium dioxide composite coating reached a corrosion efficiency of 89.29 % and an impedance modulus of 106.6Ω.cm2 after the same conditions, increasing corrosion resistance by 17.86 % compared to the pure epoxy resin. The composite coating with 10 wt% nano-kaolin exhibited superior mechanical and corrosion resistance, outperforming the 20 wt% titanium dioxide coating. Mechanical and corrosion mechanisms suggest that the uniformly dispersed nano-kaolin inhibits interactions between epoxy resin molecules and carries the external load, thereby enhancing intermolecular cohesion. Improved adhesion and impact resistance indirectly extend the coating's lifespan by prolonging the path of corrosion media through the coating to the substrate. The novel coating modification method proposed in this study effectively replaces titanium dioxide and enhances the coating's mechanical and corrosion resistance, offering a new solution for corrosion prevention in metal materials.

Research on the Microstructures and Properties of AA5052 Laser-Welded Joints with the ER4043 Filler Wire

Researches were conducted on the laser welding of 3 mm sheet-thickness lap joints of AA5052 with ER4043 filler wires. The effects of laser power on the joint morphology, microstructure, mechanical properties, and corrosion resistance were investigated. The results indicate that both increased heat input and the addition of filler wires make the molten pool more instable, which results in more process pores. Circular pores are observed in the upper part of the weld, while chain-like pores are distributed in the middle of the weld. The highest tensile strength of the weld joint is 192.61 MPa with an elongation of 10.1% at a laser power of 3.5 kW. The microhardness at the center of the weld is approximately 25% higher than the base material, which is probably because the addition of ER4043 filler wires brings more Si element to the weld. Moreover, the weld joints display superior corrosion resistance compared to the base material. These outcomes enhance the understanding of AA5052 laser welding with fillers wire and provide valuable in-sights for engineering applications.

Fabrication of a Hydrophilic Al2O3/AlN EP Coating with Self‐Cleaning and High‐Efficiency Anti‐Corrosion Properties

AbstractCurrently, with the gradual development of anticorrosive coatings, the pursuit of simple preparation methods and the improvement of anticorrosive coatings’ properties have become the major research trends. This study successfully prepared a hydrophilic super anticorrosive coating through a simple mixing method. The coating has a contact Angle of 67.8° and a rolling Angle greater than 20°. This coating can withstand 180 days of salt spray test with no bubble or rust formation when placed on a Q 235 substrate in a 3.5 wt % NaCl solution, demonstrating the excellent corrosion resistance of the AO0.4AN0.6EP coating. Furthermore, after being immersed in a 3.5 wt % NaCl solution for 3 days, the AO0.4AN0.6EP coating exhibited the largest impedance diameter (2.07×108 Ω⋅cm2), almost three times larger than other coatings, and possessed the highest Bode modulus value, one order of magnitude higher than other coatings. After immersion in a 3.5 wt % NaCl solution for 7 days, the AO0.4AN0.6EP coating had the largest Ecorr and the smallest icorr, indicating its superior corrosion resistance. In addition to corrosion resistance, the AO0.4AN0.6EP coating showed no signs of cracking, discoloration, or decomposition after being exposed to ultraviolet aging lights for 30 days, demonstrating its excellent UV resistance. Moreover, neither dry soil particles nor muddy water could adhere to the coating surface, proving its good self‐cleaning ability. Therefore, this coating holds promising applications in the field of super corrosion‐resistant coatings.

Laser powder bed fusion of Mg–Zn–Zr alloy: Formability, microstructure evolution and biodegradation behavior

Laser powder bed fusion (LPBF) was used to fabricate Mg–Zn–Zr (ZK60) parts, with a thorough investigation of processability by varying laser power and scanning rate. The combined effect of these parameters, which determines laser energy density, significantly impacted the forming quality of LPBF ZK60. Dense parts (over 99%) free of visible defects such as pores and cracks were achieved at a laser energy density of 74.1 J/mm2. The formation mechanisms of pores and cracks were extensively analyzed concerning the characteristics of the molten pool and subsequent cooling behavior. The LPBF ZK60 parts exhibited extremely fine grains, with an average grain size of 3.2 μm. Both equiaxed and columnar grains were observed, with a central equiaxed zone in the melt pool and a perpendicular lamellar zone along its boundary. Additionally, the Mg7Zn3 eutectic phase precipitated within the α-Mg matrix of ZK60. Immersion and electrochemical tests indicated that the XZ plane displayed superior corrosion resistance, attributed to fewer deformation regions and lower dislocation density. Furthermore, in vitro cell experiments confirmed that the ZK60 alloy possesses good biocompatibility.

A Study on Microstructural Evolution and Corrosion Behavior of Ti36-Al16-V16-Fe16-Cr16 High-Entropy Alloy Fabricated via Spark Plasma Sintering Technology

AbstractThis study focused on the synthesis of Ti36-Al16-V16-Fe16-Cr16 high-entropy alloys (HEAs) through spark plasma sintering to ascertain their corrosion resistance performance. Varied sintering temperatures, ranging from 700 to 1100 °C were employed to discern their impact on the alloy's characteristics. The fabricated HEAs underwent characterization using scanning electron microscopy and X-ray diffraction. A potentiodynamic polarization measurement was employed to compare the electrochemical properties of HEAs sintered at different temperatures in sulfuric and chloride aggressive media. The study outcomes indicate that the HEA sintered at 1000 °C exhibited superior corrosion resistance compared to other HEAs at other temperatures. This study contributes valuable insights into the nuanced relationship between sintering temperature, microstructure, and corrosion resistance of Ti36-Al16-V16-Fe16-Cr16 HEAs.

A review on AI-driven environmental-assisted stress corrosion cracking properties of conventional and advanced manufactured alloys

Stress corrosion cracking (SCC) poses a significant challenge to the integrity and longevity of both conventional and advanced manufactured alloys, impacting critical industries such as aerospace, marine, and nuclear energy. This review explores the use of artificial intelligence (AI) to analyse and predict SCC properties. Traditional alloys such as steel, aluminium, and titanium, as well as advanced materials such as additive-manufactured and high-entropy alloys, exhibit unique SCC behaviours influenced by corrosive environments, mechanical stress, and temperature variations. AI techniques, including machine learning models, offer transformative approaches to understanding and mitigating SCC. Leveraging extensive datasets from experiments and field studies, AI can identify patterns and correlations that traditional methods might miss. Predictive modelling through supervised learning forecasts SCC initiation and propagation, aiding in material design and maintenance. Unsupervised and reinforcement learning enhances alloy composition and processing parameter optimisation for better SCC resistance. In conventional alloys, AI identifies specific SCC conditions, leading to improved protective measures. For advanced alloys, AI-driven insights tailor additive manufacturing processes and design high-entropy alloys with superior corrosion resistance. This review includes case studies demonstrating AI's effectiveness in predicting SCC across various alloy–environment combinations, highlighting successes and challenges. Despite hurdles such as data quality and integration, AI holds immense potential to revolutionise SCC research, enhancing understanding of SCC mechanisms and fostering innovations in alloy design and preventative maintenance.

Predicting shear strength of fiber-reinforced concrete beams reinforced with longitudinal FRP bars with machine learning techniques

ABSTRACT This study investigates the shear strength prediction of Fibre-Reinforced Concrete (FRC) beams reinforced with Fibre-Reinforced Polymer (FRP) bars and without stirrups through the application of Machine Learning (ML) techniques. The utilisation of FRP bars, particularly Glass Fibre-Reinforced Polymer (GFRP) and Basalt Fibre-Reinforced Polymer (BFRP) bars, has emerged as a promising alternative to traditional steel reinforcement due to their superior mechanical properties and corrosion resistance. Moreover, the incorporation of macro- and micro-discrete fibres into concrete compositions enhances both shear and flexural behaviour while reducing crack propagation induced by tensile stresses. The primary objective of this research is to develop accurate predictive models for the shear capacity of FRP-reinforced concrete beams, considering various influential parameters. Six different ML techniques, namely Multiple Linear Regression (MLR), Gaussian Process Regression (GPR), k-Nearest Neighbors (KNN), Support Vector Machines (SVMs), Artificial Neural Networks (ANNs) and Random Forest Regression (RFR), are employed to analyse the complex interactions between input variables, such as fibre type, bar diameter, concrete compressive strength, beam dimensions and the resulting shear strength. By leveraging these computational approaches, we aim to overcome the limitations of conventional analytical methods and provide robust predictions for structural design and optimisation.

Controlled Compositions in Zn–Ni Coatings by Anode Material Selection for Replacing Cadmium

Cadmium-based coatings have long been used to protect high-strength steel in aerospace, but due to cadmium’s toxic and carcinogenic nature, its use is increasingly restricted. Zinc–nickel coatings, containing 10–14 wt% Ni, offer superior corrosion resistance compared to pure zinc, making them a promising alternative. However, Zn–Ni coatings are prone to cracking, which can compromise their protection. This study investigates how different anode materials influence crack formation and coating properties during electrodeposition. Zinc and nickel anodes produced coatings with consistent thicknesses of 13–15 µm, while 1020 steel and stainless steel resulted in thicker coatings of up to 33 µm. Notably, coatings deposited with nickel anodes demonstrated strong adhesion and consistent interface quality. Zinc anodes achieved a high Ni content of about 13.5 wt%, whereas 1020 steel and stainless steel produced lower Ni content, around 7 wt%. Additionally, zinc and nickel anodes led to fewer defects and minimal porosity, in contrast to the higher porosity observed with 1020 steel and stainless steel anodes. Furthermore, zinc anodes maintained stable voltages (~0.5 V), contributing to more uniform coatings. In terms of corrosion resistance, zinc anodes exhibited a lower corrosion rate of 0.44 mm/year compared to 1.54 mm/year for nickel anodes. This study highlights the importance of anode selection in reducing cracking and optimizing Zn–Ni coatings, presenting them as a safer and more effective alternative to cadmium-based coatings.

Achieving superior mechanical and corrosion properties in medium-thickness Ti-6Al-4 V alloy joints by back heating assisted friction stir welding below β-phase transformation temperature

The equiaxed microstructure formed below the β-phase transition point of Ti alloys generally exhibits an excellent balance of mechanical properties and corrosion resistance. However, this desirable microstructure is impossible to be obtained in fusion welded joints but is prospective to be achieved by the solid-state friction stir welding (FSW) technique. Unfortunately, it generally generates bottom defects and severe tool wear in medium-thickness Ti alloy joints when conventional FSW was conducted below the β-phase transition point. In this study, 6 mm thick Ti-6Al-4 V plates were joined by both the conventional FSW and back heating assisted FSW (BHAFSW). Defects caused by significant tool wear and bottom phase transition differences occurred in the conventional FSW. It was found that the hardness difference between the base material (BM) and the tool increased to 35.6 % from 500 °C to 900 °C. The back heating (150 °C) was used to control welding temperatures remaining the 900 °C, thus largely reducing the tool wear by increasing the hardness difference. In addition, the back temperature compensation increased the bottom temperature and controlled the phase transition position from the bottom to the middle of the joint. The shoulder pressure contributed to the compression of the defects, and the defects were eliminated by increasing the pressure at the phase transition position. A significantly refined equiaxed microstructure with an average grain size of ~0.9 μm was achieved below the β-phase transition temperature in the stir zone via back heating assisted FSW, while a bimodal structure with an average grain size of 3.5 μm was formed near the β-phase transition temperature. Inconspicuous reduction of the strength was detected for the joints (98 % of the BM) which possess equiaxed microstructures, and the corrosion resistance of the joints was enhanced compared to the BM. This superior synergy of mechanical and corrosion properties exceeded the majority of Ti alloy joints previously reported. This study provided an effective method for obtaining medium-thickness Ti alloy joints with ultrafine equiaxial structures with superior mechanical properties and corrosion resistance.

A comparative study of TiO2, Ta2O5 and Nb2O5 coated Ti6Al4V titanium alloy for biomedical applications

Refractory metal oxides such as titanium dioxide (TiO2), tantalum oxide (Ta2O5), and niobium oxide (Nb2O5) coated-titanium and its alloys for medical applications have recently gained significant attention due to their remarkable properties, including high hardness, strong chemical inertness, and excellent biocompatibility. However, comparative studies among them remain scarce. In this study, thin films of Ta2O5, Nb2O5, and TiO2 were deposited on Ti6Al4V titanium alloy using radio frequency sputtering technology. Their properties were comparably evaluated through a series of tests, including scratching, nanoindentation, friction and wear, potentiodynamic polarization, and cell cultivation experiments. The results revealed that all three coatings, with a thickness of approximately 2.6–2.8 μm, exhibited an amorphous columnar growth pattern with dense surfaces resembling cauliflower. The bonding force of the TiO2 coating exceeds 50 N, which is 26.2 times and 14.5 times greater than that of Ta2O5 and Nb2O5, respectively. Furthermore, all coated samples demonstrate superior wear resistance, corrosion resistance, and biocompatibility compared to bare Ti6Al4V. Among the coatings, TiO2 showed the best performance, followed by Ta2O5, while Nb2O5 exhibited the least favorable performance. These findings revealed the performance differences among the three ceramic coatings on Ti6Al4V samples and offer valuable insights for further research and the selection of coatings to enhance the properties of Ti6Al4V titanium alloy for biomedical applications.