Wire and Arc Additive Manufacturing (WAAM) has emerged as an efficient technology for producing large-scale metallic components, achieving up to 90

Recent advances in additive manufacturing (AM) have transformed manufacturing and engineering. Direct energy deposition with arc and wire (DED-Arc) stands out due to its high deposition rates, cost-effectiveness, material efficiency, and environmental benefits. DED-Arc is ideal for producing large and medium-complexity metal components, distinguishing it from traditional and other AM methods; however, limited research has been conducted on thick-walled parts compared to single-walled ones. This study investigates the microstructure and anisotropy of mechanical properties in 316L stainless steel parts manufactured using DED-Arc with various deposition strategies. Through parameter optimization, this research achieves the successful fabrication of large-walled components, highlighting the crucial role of deposition parameters in their production. Analysis of X-ray diffraction (XRD) peaks related to the (111) and (200) planes of the austenite phase reveals the development of crystallographic texture post-weld, further supported by electron backscatter diffraction (EBSD) analyses indicating a pronounced presence of texture. Scanning Electron Microscope (SEM) analyses identify distinct ferrite phase morphologies in different component regions. Mechanical testing suggests a bias toward anisotropic behavior in DED-Arc materials, with 45° overlap angle samples demonstrating slightly superior mechanical properties. Consistent microhardness along the build direction underscores the reliability of the deposition strategy. Residual stresses were investigated using XRD on the outer surfaces of all DED-Arc samples, and profiles analyzed away from the substrate show only compressive stresses. Changing the overlap angle changes the texture intensity of the parts.

This research investigates the influence of Nb2O5 coatings, produced by using reactive sputtering technique, on the surface of middle-tension specimens M(T), regarding fatigue crack growth curves (da/dN versus ΔK) under exposure to a 0.6 mol L–1 NaCl saline solution. Results demonstrated the corrosion process occurred in the vicinity of the crack tip, where stresses are elevated, and significant plastic deformation prevails, notably influenced by slip bands that induce microcracks, exposing fresh material layers to the corrosive surroundings. The Nb2O5 coatings enhanced the fatigue-corrosion resistance of the 2198-T851 aluminium alloy. This study marks an initial step towards more comprehensive investigations into the impact of Nb2O5 coating on improving the mechanical properties of the 2198-T851 aluminium alloy.

Wire Arc Additive Manufacturing (WAAM) has gained significant interest from industry and academia for its ability to combine the benefits of additive manufacturing (AM) in producing large components with simple contours, gradual curvatures and moderate inclinations. The competitive advantages combine cost-effectiveness and material efficiency. This work presents and analyse microstructure, mechanical properties and corrosion behaviour of 316L stainless steel (316L SS) parts manufactured by WAAM with various deposition strategies. Austenite, ferrite phases and inclusions were identified through Backscattered Electron Scanning Electron Microscopy (BSE-SEM). Digital Image Correlation (DIC) results revealed the influence of weld bead interfaces on the mechanical behaviour, indicated by regions of necking and variable strain rates nearby fusion lines. Grain size was a crucial factor responsible for deformation and mechanical properties. Samples with hybrid (HY) and zigzag (ZZ) deposition strategies at the 90° overlap, presented better mechanical properties compared to the 45° (HY45 and ZZ45). Electrochemical methods, including potentiodynamic polarisation curves (PPc) and electrochemical impedance spectroscopy (EIS), assessed the response of the samples to corrosive environment. Corrosion results demonstrated that the performance of corrosion resistance as a function of time presented by HY90 and ZZ90 samples were better than HY45 and ZZ45 ones. Additionally, corrosion products enhanced the corrosion resistance of WAAM-manufactured 316L SS alloys. The results indicate that the 90° overlap is a promising strategy to improve both mechanical properties and corrosion resistance of 316L SS produced by WAAM.

Friction stir welding (FSW) has emerged as an alternative to conventional joining processes for high-strength metal alloys, offering advantages in material efficiency and cost-effectiveness. However, the microstructural changes induced by FSW influence the mechanical and corrosion properties of aluminium alloys. To address these issues, anticorrosive coatings based on niobium pentoxide (Nb2O5) deposited via the physical vapour deposition (PVD) technique appear as a promising strategy to mitigate corrosion in the FSW-affected regions. This study aims to understand the corrosion behaviour of the 2198-T8 alloy post-FSW (nugget zone - NZ) and evaluate the protective efficacy of Nb2O5 coatings. Global electrochemical analyses, including open circuit potential (OCP), potentiodynamic polarisation curves (PPc), and electrochemical impedance spectroscopy (EIS), were conducted in 0.6 mol L- 1 NaCl solution for the 2198-T8, 2198-T8/FSW, and 2198-T8/FSW/Nb2O5 specimens. A comparative analysis of the uncoated samples revealed that the NZ exhibited reduced corrosion resistance compared to the base material (BM). However, the Nb2O5 coating produced using the PVD technique was able to delay the appearance of pitting on the surface of the 2198-T8/FSW alloy in 0.6 mol L- 1 NaCl solution. The results demonstrate the efficacy of Nb2O5 coatings in safeguarding the 2198-T8/FSW aluminium alloy against aggressive chloride environments, thereby enabling a more effective application of innovative joining techniques such as the FSW process.

This investigation examined the efficacy of Nb₂O₅-based coatings, deposited by using the reactive sputtering technique, on the corrosion and corrosion-fatigue behaviour of 2198-T8 aluminium alloy used as aircraft material. Global corrosion behaviour was accessed by Open Circuit Potential (OCP), Potentiodynamic Polarization curves (PPc) and Electrochemical Impedance Spectroscopy (EIS) techniques in 0.6 mol L⁻1 NaCl solution. Fatigue crack growth (FCG) tests were conducted under controlled loading conditions in both air and saline environments. Comprehensive structural and morphological characterisations were performed using advanced microscopy and spectroscopy techniques, including Atomic Force Microscopy (AFM), Scanning Electron Microscopy/Energy Dispersive X-ray Spectroscopy (SEM/EDX), Raman spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), and Electron Backscatter Diffraction (EBSD). The results unequivocally demonstrated the protective nature of the coating, significantly enhancing the alloy's durability as evidenced by corrosion and fatigue-corrosion tests. These findings underscore the substantial potential of Nb₂O₅ coatings in extending the service life of 2198-T8 aluminium alloy when subjected to aggressive environments, thereby providing invaluable data for aerospace engineering applications.

This research investigated multilayer coatings created on AISI 304L steel by using physical vapor deposition associated with high-power impulse magnetron sputtering and dynamic glancing angle deposition. The coatings were subject to an extensive analysis, which included structural, electrochemical, mechanical, and tribological. The findings indicated that the coatings exhibited a periodic zig-zag nanostructure characterized by a corrugated pattern in the sublayers. This architecture was achieved through the dynamic modulation of the angular co- ordinates of the vapor source. The hardness an upward trend from 25 GPa (no substrate oscillation, 0 degrees) to approximately 33 GPa for intermediate pendular displacements of +10 degrees and +15 degrees. Wear performance was most effective for pendular displacements of +5 degrees, +10 degrees, and +15 degrees, showcasing significantly reduced wear rates. The +10 degrees condition exhibited wear volumes approximately 7.5 and 5 times smaller compared to the 0 degrees and +25 degrees conditions, respectively. The conditions of +5 degrees, +10 degrees, and +15 degrees exhibited a corrosion protection efficiency exceeding 98 %, whereas the 0 degrees condition demonstrated an efficiency of merely 58 % when exposed to a 0.5 mol L-1 sulfuric acid solution.

Niobium-based oxides have garnered increased attention in recent years for their remarkable enhancement of corrosion resistance, as well as biofunctional properties of various metallic materials, including 316L SS. However, the mechanical properties of these promising coatings have not been fully elucidated. This study investigated how much the environmental conditions (air, artificial saliva, and NaCl solution) impact the wear performance of 316L SS without and with Nb2O5 coatings deposited via the reactive sputtering technique. The results exhibited a notable decrease in friction coefficient (55% in air, 18% in artificial saliva, 10% in 0.9 wt% NaCl solution), wear area (46% in air, 36% in AS, 17.5% in 0.9 wt% NaCl solution), and wear rate (44.0% in air, 19.5% in AS, 12.0% in 0.9 wt% NaCl solution). Ultimately, the results obtained in the present study elucidate the synergistic mechanisms of corrosion and wear in 316L SS containing Nb2O5 coatings, highlighting its significant potential for applications in the biomedical sector.

Abrasive wear is a principal cost in mining and mineral processing operations. High chromium white cast iron (WCI) further reinforced with niobium carbide (NbC) shows promise to increase component wear lives. This work investigates the effect of niobium macro-additions on microstructure, hardness and high-stress abrasive wear behaviour of Nb-containing high-Cr WCIs. Eight alloys with Nb between 0 and 10.7 wt% were produced by sand casting. Increasing niobium carbide volume fraction (Nb-CVF) increased hardness from 724 to 812 HV (7.3 HV per 1% Nb-CVF). Abrasive wear resistance, assessed using the ball mill abrasion test in basalt (less competent) and quartzite (competent rock), showed clear beneficial effect of NbC macro-addition up to 11.4 and 7 vol% in basalt and quartzite, respectively. These correspond to life improvements of 37% and 7% per 1% Nb-CVF in the optimum range of Nb macro-addition, in basalt and quartzite respectively. Micro-mechanistic observations of worn surfaces showed that NbC particles not only protrude from the matrix but do so more than Cr-rich M7C3 carbides. In deep wear grooves created by quartzite, M7C3 particles were cut flush with the matrix, whereas NbC protruded, visibly impeding the progress of the abrasion event.

Revealing the frictional behavior through the lens of structural and chemical evolution is crucial for comprehending the exceptional wear-resistance of alloys with complex composition. Here, we propose that superior wear resistance can be achieved via dynamic surface segregation during sliding at room temperature. This strategy was demonstrated in CrCoNi multi-principal element alloy (MPEA) films with nano-grain structure, which exhibit a remarkably low wear rate that is <50 % of that for their VCoNi counterpart. Such distinct wear behavior is attributed to the specific friction-driven Ni segregation on the CrCoNi surface, which facilitates the preferential oxidation and formation of a nanocomposite protective layer with equiaxed nanograins uniformly embedded in an amorphous matrix. This wear-induced unique microstructure accommodates sliding-induced plastic deformation against damage and is responsible for the superior wear-resistance. Having revealed these fundamental mechanisms by experiment and simulation, this study provides a brand-new perception for designing self-adaptive MPEA surfaces. This involves adjusting the evolution of deformation layers with specific structure and chemistry, precisely engineered for tribological applications.

This work investigates the application of Friction Stir Process (FSP) to the ZK60 alloy enhanced with 1.5 % mischmetal (ZK60-1.5 wt% Mm) combined with manual filing to achieve significant improvement in the hydrogen storage properties of this alloy. Addition of 1.5 wt% Mm to the ZK60 alloy yields a matrix with high thermal stability, attributable to the formation of high melting point intermetallic phases. Post FSP, the ZK60-1.5 wt% Mm material shows a refined, pulverized, and recrystallized structure. Such a structure allows the acquisition of filings with nanometric particle sizes and even more pulverized intermetallic phases post-FSP. This synergistic approach produces a significantly homogeneous microstructure morphology, facilitating the study of the catalytic role Mm plays in the hydrogen storage kinetics of the ZK60 alloy at 350 degrees C. Currently, among all Severe Plastic Deformation (SPD) techniques, only FSP followed by manual filing has demonstrated a capacity to provide a nanometric, homogeneous microstructure that significantly enhances hydrogen storage kinetics and cycling properties. Additionally, the combination of FSP and manual filing is an industrialization process that can be easily implemented, offering reliability, controllability, and cost-effectiveness compared with alternative methods like High-energy Ball Milling (HEBM). Experimental kinetic data for (de)hydrogenation reactions were analyzed using the Luus-Jaakola optimization method, underscoring the potential applicability of the FSP-manual filing route for hydrogenation temperatures <350 degrees C.

Friction Stir Welding (FSW) emerges as a compelling solid-state welding technique for aluminium alloy components used as aircfrat materials. Despite being a solid-state process and mitigating numerous solidification challenges, it retains its thermomechanical nature, affecting the material's microstructure and, consequently, its mechanical properties. This concise communication sought to assess the impact of the FSW process on the micro-adhesive wear and microhardness properties of the 2524-T3 alloy. The results showed that the FSW process was executed successfully on 2524-T3 aluminium alloy plates as well as the great influence of intermetallic particles on hardness and micro-adhesive wear.

Magnesium alloys offer an alternative for applications in biodegradable implant devices within human body, eliminating the need for subsequent surgeries to remove metallic parts. Nevertheless, the uniform degradation rate of magnesium (Mg) alloys must be enhanced by applying surface coatings, preferably incorporating bactericidal and biocompatible agents, to improve the implant properties. In this study, magnesium alloys ZK60 (Mg, Zn, and Zr) and ZK60-Mm (Mg, Zn, and Zr with 1.5% mass of rare-earth elements - mischmetal), both having a specific mass close to the bone, were investigated. The surfaces were coated with ZnO using physical vapor deposition (PVD) in the HiPIMS (High Power Impulse Magnetron Sputtering) mode. The corrosion resistance and degradation of the alloys were studied using electrochemical and immersion tests in simulated body fluid. Surface analysis and microstructures were characterized using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), and X-ray Diffraction (XRD). The results showed that the ZnO coating favors osseointegration with hydroxyapatite formation after immersion in SBF. Moreover, electrochemical analysis indicates an enhancement in corrosion resistance. On average, the corrosion current density decreases by a factor of four for the ZK60 alloy and two for the ZK60-Mm alloy post-coating. The corrosion rate of ZnO-coated alloys is lower compared to that of uncoated alloys, showcasing the promising utility of this coating.

Nanocrystalline thin films find extensive applications due to their high mechanical strength and wear resistance. However, the challenge is to prevent unwanted grain growth during operation, especially at high temperatures, due to the increased grain boundary volume, which elevates the system's overall energy. Addressing this issue necessitates identifying optimal heat treatment conditions and selecting appropriate chemistry to stabilize grain boundaries. This study investigates the grain growth and phase evolution within Ti-Cr-Zr magnetron sputtered nano multilayers with 5 and 10 nm individual layer thickness, subjected to vacuum heat treatment at 1100 degrees C for 5 and 10 min. Characterization involved X-ray Photoelectron Spectroscopy (XPS), X-Ray Diffraction (XRD), and Transmission Electron Microscopy (TEM). During deposition, evidence of diffusion was observed as the multilayers formed Cr4TiZr, TiCr2, and Cr2Zr, phases. The Ti-Cr-Zr nanoscale system multilayers with 10 nm individual layer thickness also exhibited the emergence of Ti0.3Zr0.7 phase. During heat treatment grain growth occurred, after 10 min an average grain size of 173.7 nm and 119.1 nm was noted for the Ti-Cr-Zr nanoscale system multilayer with 5 nm and 10 nm individual layer thickness, respectively. The different growth rates are attributed to their distinct interfacial volumes, influencing the reaction velocity due to the variations in nanolayer thickness. No new phases were formed after heat treatment for the case of 10 nm individual layer thickness coating. However, 5 nm individual layer coatings showed the emergence of Ti0.3Zr0.7 phase, not present after deposition. In conclusion, this research achieved the desired nano grain stabilization of the Ti-Cr-Zr system nanoscale multilayers after heat treatment at 1100 degrees C for 10 min. This process led to the complete decomposition of the multilayer structure, resulting in the formation of grains smaller than 200 nm, marking a significant step toward the effective control of grain growth in nanocrystalline materials.

This work aims to investigate the influence of niobium and carbon nanostructured coatings on the corrosion resistance of the 316L SS. The coated and uncoated specimens were morphologically and structurally characterized by using OM, SEM/EDX, DRX, FTIR, Raman spectroscopy and XPS techniques. The corrosion behaviour was assessed by OCP, PPc, EIS as well as immersion tests in 0.6 mol L-1 NaCl solution. In addition, the average contact angles were used to evaluate the surfaces free energy by the Van Oss interfacial tension component theory approach. Results showed that the surface treatments positively influenced the corrosion resistance of the 316L SS and the coatings act as a protective barrier against corrosion process. The reactive sputtering technique increased the wettability of the surfaces in relation to the base material. Considering applications in aggressive media, the 316L SS/Nb2O5 specimen exhibits superior performance when compared to the base material and 316L SS/carbon.

This work investigates the fatigue crack growth (FCG) behaviour of the 2524-T3 aluminium alloy uncoated and coated with reactive sputtered nanostructured Nb2O5 thin films. Fatigue and Fatigue-corrosion tests were carried out in air and an aggressive medium at a stress ratio R = (Kmin/Kmax) of 0.1, employing frequencies of 10 Hz (air) and 0.1 Hz (0.6 mol L-1 NaCl solution), using a sinusoidal waveform. The Nb2O5 coatings were found to positively modify the FCG resistance of the 2524-T3 alloy for the same value of stress intensity factor (ΔK), acting as a protective barrier against localised corrosion process, and reducing FCG rates in aggressive environment. • Fatigue-corrosion tests were performed in sodium chloride solution. • Middle-Tension M(T) specimens were functionalized by using reactive sputtering technique. • The reactive sputtering technique was able to produce Nb2O5 coatings on the 2524-T3 Al alloy. • Nb2O5 coatings decreased the fatigue crack growth rates by 25

Geopolymer materials are a promising and eco-friendly alternative to Portland cement. This work investigates the combined effect of a-alumina (a-Al2O3) content, temperature, and curing conditions on the mechanical properties of metakaolin-based geopolymers containing a-Al2O3. The influence of a-Al2O3 content and curing temperature (T-c) were evaluated using a central composite design. The geopolymers were developed from metakaolin/a-Al2O3 mixtures activated with a NaOH solution, uniaxially pressed (33 MPa/30 s), and cured at the experimental design temperatures under different conditions: i) curing for 24 h; ii) pre-curing at room temperature for 24 h and curing for 24 h and iii) pre-curing for 24 h and curing for 48 h. Statistical analyzes were performed to evaluate the variables' significance (a-Al2O3 content and T-c) and their interactions. Response surfaces modeling and mathematical models were described to predict the flexural strength values as a function of each curing condition. The results showed that temperature and curing time has an essential role in the flexural strength (s(f)), with the temperature being a significant factor in all experimental conditions evaluated. Inserting a pre-curing step at room temperature for 24 h favored the increase in sf values. Furthermore, regardless of the % a-Al2O3, the sf for samples with pre-curing did not vary significantly with the curing time.

The multi-principal nitride film is known for its high hardness, good corrosion resistance, but its limited toughness severely reduces its wear resistance. This study presents a VCoNiN weak-nitride-forming system with unique microstructure of nanocrystalline embedded in amorphous matrix. The VCoNiN system demonstrates superior hardness to the VCoNi multi-principle alloy film and VN metal nitride film. Moreover, it exhibits the lowest wear rate against Si3N4 at room temperature. The exceptional mechanical properties and excellent oxidation resistance derived from the multi-principal system contribute to the superior wear resistance of VCoNiN. Additionally, the novel microstructure allows for more uniform deformation during wear as the nanocomposite structure accommodates plastic strain without cracking or localized brittle fracture. This provides a promising design strategy for weak-nitride-forming film with enhanced wear resistance by enhancing the plastic deformation ability of brittle nitride.