Search Results (376)

Titanium and its alloys are widely used in orthopedic and dental implantology for their corrosion resistance and biocompatibility supporting osseointegration; however, their usage is accompanied by release of wear debris that may induce inflammatory responses. The necessity of formation of multifunctional coatings that accelerate osseointegration and provide long-term mechanical stability of titanium implants remains highly relevant. We propose a new simple and scalable coating method based on the laser shock processing technique, with TiO₂ and SrCO₃ powder mix used as an absorption layer. Our results show that this treatment created an approximately 158.3 ± 35.8 μm thick coating consisting of a mixed SrTiO₃-TiO₂ phase. The hardness of this coating evaluated by Vickers microhardness measurements showed a hardness increase of 3.3 times compared to the initial titanium substrate. Piezoelectric force microscopy (PFM) analysis revealed the presence of a reverse piezoelectric effect in the obtained structure confirming the highly likely successful synthesis of coating impregnated with SrTiO₃. This piezoelectric coating can be readily deposited onto titanium substrates using the proposed method, enabling exploration of potential biomedical applications in future research. Full article

In this work, micro/nano-scale (TiB₂ + TiC)/Al composites with reinforcement contents ranging from 0 to 30 wt.% were fabricated by the combination of Ti-B₄C reactive sintering and spark plasma sintering (SPS). The results indicate that a sintering temperature of 1400 °C is essential for achieving a complete reaction between Ti and B₄C, successfully producing a bimodal TiB₂-TiC reinforcement consisting of nano-scale and micro-scale particles. Microstructure analysis reveals that the addition of micro/nano-scale TiB₂ and TiC ceramic particles significantly refines the grain size of the Al matrix from 11.52 μm in pure Al to 1.09 μm in the 30 wt.% (TiB₂ + TiC)/Al composite. As the TiB₂ and TiC contents increase, Vickers hardness and compressive yield strength increase progressively, while the uniform compressive plastic strain first increases and then decreases. The 20 wt.% (TiB₂ + TiC)/Al composite demonstrates the optimal comprehensive properties, with a compressive yield strength of 196.4 ± 6.1 MPa, an ultimate strength of 914.6 ± 20.1 MPa, and a uniform plastic strain of ~73.2%, as well as minimal wear rates of (3.143 ± 0.194) × 10⁻⁴ mm³/(N·m), 1.676 ± 0.251× 10⁻³ mm³/(N·m) and (3.093 ± 0.335) × 10⁻³ mm³/(N·m) at 1 N, 3 N, and 5 N, respectively. This improvement stems from the combined effects of grain refinement, dispersion strengthening, enhanced load-bearing capacity and reduced adhesive wear via the TiB₂ and TiC reinforcements. Full article

The effects of laser shock peening (LSP) on subtractively manufactured (SM) and additively manufactured (AM) Ti–6Al–4V alloys in pH 2 buffer solution were investigated. LSP increased the surface roughness from 0.25 ± 0.05 μm to 0.6 ± 0.1 μm, raised Vickers hardness by 12–16%, and introduced compressive residual stresses of 400–950 MPa. Microstructural analysis indicated that LSP promoted β-phase formation and grain refinement in SM alloys, while reducing the α′-phase fraction in AM alloys. Electrochemical testing revealed that all LSP-treated specimens exhibited active–passive transitions, unlike the stable passive response of unpeened samples. The corrosion rate (i_corr) decreased from approximately 5 × 10⁻⁶ to 1 × 10⁻⁶ A·cm⁻² after LSP. During 24 h potentiostatic polarization at 1.3 V_SCE, the passive current density stabilized at 10⁻⁸–10⁻⁷ A·cm⁻², with LSP AM specimens exhibiting values approximately twice those of their unpeened counterparts. Mott–Schottky analysis confirmed that the donor density (N_D) in the SM alloy changed negligibly after LSP, indicating a stable passive alloy. In contrast, the N_D for the AM alloy increased from 1 × 10¹⁹ to 3 × 10¹⁹ cm⁻³, suggesting an oxygen-vacancy-rich, less stable passive film. Overall, LSP reduces the corrosion rate primarily through the introduction of compressive residual stress but may impair the long-term passive-film stability of AM Ti–6Al–4V owing to defect generation. In contrast, the SM alloy maintains passive-film stability under identical treatment conditions. Full article

Gravity casting and semi-solid extrusion were employed to prepare Mg₂Si-Al composites. X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), EDS analysis, Vickers hardness testing, and tensile testing were used to compare the microstructures and mechanical properties of the two composites, aiming to clarify the effects of the fabrication processes and aging times on their microstructures and mechanical performance. The findings show that semi-solid extrusion converts dendritic α-Al into spherical or ellipsoidal grains (60 ± 25 μm) and induces the spheroidization of Mg₂Si reinforcing phases (29 ± 12 μm). Vickers hardness data show that both composites exhibit a rise-and-fall hardness trend with an increasing aging time, reaching a maximum at 8 h. At this aging stage, the semi-solid extruded composite has a Vickers hardness of 214 ± 32.71 HV, 22.99% higher than that of the gravity-cast composite under the same treatment. Tensile tests demonstrate that the semi-solid extruded composite attains its best tensile strength (254 MPa) and elongation (3.26%) at 8 h of aging. Compared with the semi-solid extruded composites aged for 4 h and 16 h, the 8 h-aged sample exhibits 32.30%/49.41% higher tensile strength and 52.34%/38.72% higher elongation, respectively. After 8 h of aging, the semi-solid extruded composite shows a 59.75% increase in tensile strength and an 88.44% increase in elongation compared with the gravity-cast composite. Full article

Erosion–corrosion at elevated temperature represents a critical degradation mechanism in components exposed to particle-laden gaseous flows, such as industrial boilers and combustion systems. This study evaluates the combined erosion–corrosion behaviour of atmospheric plasma-sprayed (APS) coatings based on Al₂O₃/TiO₂ (97/3, 87/13, and 50/50 wt.%), TiO_2, and a hybrid Al₂O₃/NiCrAlY (90/10 wt.%) system. Coatings were characterised by scanning electron microscopy, X-ray diffraction, Vickers microhardness and porosity analysis, and subsequently tested under solid particle erosion and cyclic oxidation at 200 and 400 °C with impact angles of 30° and 90°. All coatings exhibited significantly higher hardness (446–597 HV) than the AISI 310 substrate (181 HV), together with distinct differences in porosity and interlamellar cohesion. Erosion rates decreased with increasing temperature for both impact angles; however, the synergistic contribution to total degradation increased, particularly under normal impact (90°). This behaviour indicates that thermochemical activation enhances the nonlinear interaction between mechanical damage and oxidation. Coatings with lower defect connectivity showed reduced synergistic effects, demonstrating that microstructural architecture governs the magnitude of combined degradation. The Al₂O₃/NiCrAlY system exhibited improved thermomechanical stability associated with the formation of protective Al- and Cr-rich oxides. Full article

Recurrent acidic exposure in patients with gastroesophageal reflux disease (GERD) accelerates the degradation of provisional restorative materials, whereas approaches to enhance the acid resistance of 3D-printed restorations remain inadequately characterized. This study aimed to evaluate the effect of graphene oxide (GO) incorporation on the surface properties and acid resistance of 3D-printed provisional restorative materials under simulated gastroesophageal reflux conditions. GO was synthesized using the Hummers’ method and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. XRD analysis demonstrated a pronounced shift in the characteristic peak (2θ) from 26° to 12°, consistent with an expansion of interlayer spacing after oxidation. FTIR confirmed the presence of oxygen-containing functional groups (hydroxyl, carbonyl, and epoxy), while Raman spectroscopy identified the characteristic D and G bands, confirming successful GO synthesis. Temporary Crown & Bridge resin (TC100) was modified with GO at six concentrations (0, 0.025, 0.05, 0.1, 0.5, and 1.0 wt %) using a planetary ball milling technique. Standardized 3D-printed specimens (n = 24 per group) were fabricated. Surface roughness and Vickers microhardness were measured before and after 45 h of immersion in simulated gastric acid (pH 2). Data were analyzed using one-way ANOVA and paired t-tests (α = 0.05). After acid exposure, the control group (0 wt % GO) exhibited significant surface deterioration, showing the highest surface roughness and a marked reduction in hardness (p < 0.05). Conversely, GO-modified groups demonstrated a concentration-dependent improvement in resistance to acid-induced degradation. The 0.5 wt % GO group showed the most favorable performance, maintaining both surface roughness and hardness with no significant difference from baseline values (p > 0.05). These findings indicate that GO incorporation enhances the surface integrity and acid resistance of 3D-printed provisional resins, with 0.5 wt % identified as the optimal concentration for minimizing acid-induced surface deterioration. Full article

Icing poses significant operational and safety risks in aviation, especially for engine components such as cowls and baffles. This study explores the potential of a chemically exfoliated graphene-rich carbon platelet epoxy coating to improve the anti-icing and de-icing performance of 3003-H14 aluminum alloy, which is widely used in such applications. Chemically exfoliated graphite was incorporated into an epoxy resin, then applied to aluminum substrates. Characterization of the coated samples revealed ~30% improvement in surface Vickers hardness (HV) (HV 75.6 ± 1.15 vs. HV average of 98.3 ± 1.5) and enhanced thermal dissipation, with coated surfaces cooling from 104 °C to 22 °C in 530 s compared to 870 s for uncoated samples. While anti-icing performance was not directly evaluated, the observed improvements in thermal dissipation and surface hardness suggest that chemically exfoliated graphene-rich carbon platelet coatings could be promising for passive anti-icing applications. The literature suggests that graphene coating improves hydrophobicity, reducing ice adhesion and delaying nucleation due to its low surface energy and nanoscale roughness, thereby supporting potential passive anti-icing functionality for aircraft engine components. SEM analysis confirmed a uniform, compact coating layer. These preliminary findings indicate that chemically exfoliated graphene-rich carbon platelet coatings can deliver multifunctional performance—mechanical, thermal, and surface—making them promising candidates for passive anti-icing/de-icing solutions in engine components where conventional systems are ineffective. Full article

In order to provide clinically significant evidence on the long-term functional performance of CAD/CAM provisional materials, especially 3D-printed and milled resins, accurate tribologically in vitro wear tests that integrate wear parameters and surface topography analysis are necessary. The goal of the study was to assess the wear resistance of several CAM-obtained dental crown materials and the relationship between wear and the manufacturing process, distinctive postprocessing, microhardness, microroughness, and surface topography. A standardized ball-on-flat tribological protocol was applied to (n = 70) CAD/CAM-fabricated PMMA specimens (four 3D-printed groups with distinct post-processing protocols (Optiprint) and three milled materials (TelioCAD, Shaded PMMA, Copra Temp Symphony)) to quantify wear parameters micro- and nanoroughness (Ra, Rz, Sa, Sy), and Vickers microhardness, followed by comprehensive statistical analysis (t-tests, Pearson correlations) to elucidate material- and process-dependent differences in wear behaviour. Nanoroughness was carried using atomic force microscopy evaluation. Wear testing showed that most materials, particularly the 3D-printed groups, developed limited wear, whereas the milled materials evolved toward groove-dominated wear topographies. Wear statistics showed that the printed resins consistently had an advantage, meaning that the degree and rate of wear are significantly influenced by the manufacturing process. Hardness has a central role in governing the wear performance of interim resin materials, while nanoroughness acts as a secondary factor. Optimised post-processing of printed materials, particularly a prolonged post-curing period, yields a beneficial combination of low wear and specific topography, thereby providing a significant clinical advantage. Full article

Previous research indicates that WC-12Co contents above 60 wt.% in feedstock powders for cermet coatings impair adhesion and wear resistance. This study characterizes NiCrFeSiAlBC coatings—unreinforced or reinforced with 65 wt.% or 85 wt.% WC-12Co—applied via high-velocity oxy-fuel (HVOF) spraying onto stainless steel substrates under controlled parameters. It quantifies the influence of high carbide volume fractions within the NiCrFeSiAlBC matrix on microstructure and tribomechanical performance. Microstructural analysis revealed uniformly distributed cermet layers featuring dissolved reinforcements and WC hard phase formation, with minimal W₂C crystallization. Elevated WC-12Co incorporation promoted densification and reduced porosity. Vickers microhardness tests (HV 0.3) demonstrated increased hardness upon WC-12Co addition, attributable to finer particle sizes, lower porosity, and the presence of WC phases alongside crystallographic refinements. Under dry reciprocating sliding conditions, friction coefficients and wear volumes decreased markedly. Consequently, the coating with 85 wt.% WC exhibited the best mechanical and tribological properties. Full article

This paper presents results from statistical tests on random parameters of strength properties of steel used to manufacture corrugated webs for SIN plate girders, depending on the place of specimen cut-out, that is, from the flat section or ridge of the wave. The tests were performed on specimens collected from 12 randomly selected corrugated sheets with thicknesses of 2, 2.5 and 3 mm, provided by the manufacturer of SIN beams. The analysis was used to select variation coefficients of yield strength V_Re = D(R_e)/E(R_e) and partial coefficients of yield strength γ_m for steel in flat and arched parts of the web. Metallographic and Vickers hardness tests were performed. Values of deformations and residual stresses were determined. The close correlation between the influence of the web plate shape and the strength parameters along the web curvature was demonstrated. Analysis of the initiation points of stability loss (IPLS points) revealed that the initiation of stability loss occurs in the area of the flat web sections. In addition to the influence of geometry, the influence of the change in yield strength, as identified in this paper, can be observed. Consideration of random features of yield strength and web thickness can lead to modifications in designing and calculating structures made of SIN girders. Full article

This research examines how atmospheric plasma spraying torch power and coating thickness jointly affect the adhesion strength, microstructure, porosity, and flexural behavior of $A{l}_2{O}_3$ coatings on 100Cr6 steel substrates. Optical microscopy, SEM and EDS mapping, 3D surface-roughness analysis, Vickers hardness testing (HV2) on polished cross-sections, and three-point bending of extracted beams were employed to develop a processing–structure–property map. This multi-technique approach enables the cross-validation of processing–structure–property relationships and supports a robust identification of the optimal power–thickness condition by jointly considering porosity (densification), adhesion strength, flexural response and failure mode. All conditions resulted in an average surface roughness Ra of approximately 1.0 µm. Increasing torch power to 45 kW generally reduced cross-sectional porosity, except at 500 µm, where globular pores appeared. Hardness (HV2) increased with power and peaked at the intermediate thickness (500 µm); adhesion up to 63 MPa was recorded for the 300 µm/45 kW coating. Flexural strength was highest at 500 µm and was consistently greater at 45 kW than at 39 kW. Fractography showed a shift in failure mode from interface-driven delamination at 39 kW to more cohesive, tortuous intra-coating cracks at 45 kW, aligned with improved splat bonding and crack-path deflection. An intermediate thickness of 500 µm deposited at 45 kW is thus identified as an optimal condition to balance densification and crack-path tortuosity, leading to enhanced hardness and flexural performance. Full article

Wire Arc Additive Manufacturing (WAAM) is a cost-effective method for fabricating large aluminum components; however, it tends to suffer from heat accumulation and coarse anisotropic microstructures, which can limit the part’s performance. In this study, a wall is fabricated using a hybrid unified additive deformation manufacturing process (UAMFSP) method, which integrates friction stir processing (FSP) into WAAM, and is compared with a Metal Inert Gas (MIG)-based WAAM wall. Infrared (IR) thermography revealed progressive heat buildup in MIG walls, with peak layer temperatures of about 870 to 1000 °C. In contrast, in the UAMFSP process, heat was redistributed through mechanical stirring, maintaining more uniform sub-solidus profiles below approximately 400 °C. Also, optical microscopy and quantitative image analysis showed that MIG walls developed coarse, dendritic grains with a mean grain area of about 314 µm², whereas the UAMFSP produced refined, equiaxed grains with a mean grain area of about 10.9 µm². Microhardness measurement (Vickers HV0.2, 200 gf) confirmed that the UAMFSP process can improve the hardness by 45.8% compared to the MIG process (75.8 ± 7.7 HV vs. 52.0 ± 1.3 HV; p = 0.0027). In summary, the outcomes of this study introduce the UAMFSP process as a method for addressing the thermal and microstructural limitations of WAAM. These findings provide a framework for further extending hybrid additive–deformation strategies to thicker builds, alternative alloys, and service-relevant mechanical evaluations. Full article

To address the trade-off between thermoelectric efficiency in oxide thermoelectric materials used in Aiye Processing Equipment, this study investigates the effect of La doping on the thermoelectric properties of indium oxide (In₂O₃) through experimental characterization and mechanism analysis. The results show that La doping induces synergistic optimization of the electronic structure, lattice dynamics, and defect state of In₂O₃, leading to simultaneous enhancements in thermoelectric and mechanical properties. Specifically, La³⁺ substitution for In³⁺ significantly increases carrier concentration, which, combined with the band convergence-induced elevation of density of states (DOS) near the Fermi level, results in a remarkable improvement in power factor (from the intrinsic enhancement driven by electrical conductivity) while mitigating the reduction in Seebeck coefficient. Meanwhile, lattice distortion caused by ionic radius mismatch and decreased Young’s modulus (due to weakened In-O bonds) jointly enhance phonon scattering and reduce phonon propagation velocity, leading to a significant decrease in lattice thermal conductivity and total thermal conductivity. Consequently, the thermoelectric figure of merit (ZT) of La-doped In₂O₃ increases from 0.055 to 0.358, a six-fold enhancement. Additionally, La doping improves Vickers hardness through three synergistic mechanisms: internal stress from lattice distortion, enhanced interatomic bonding (synergistic reinforcement of ionic and covalent bond components), and dislocation pinning by substitutional defects (La_In). This study demonstrates that La doping achieves the dual regulation of “promoting electrical transport, suppressing thermal conduction, and enhancing mechanical strength” in In₂O₃, breaking the traditional trade-off between thermoelectric and mechanical properties. The findings provide a feasible strategy for the performance optimization of oxide thermoelectrics and lay a foundation for their practical applications in energy conversion systems requiring high efficiency and structural reliability. Full article

The microstructure evolution law and the changes in mechanical properties of 442 ferritic stainless steel after annealing treatment at different temperatures are systematically investigated. The results show that, as the annealing temperature increases, the cold-rolled 442 ferritic stainless steel successively undergoes the process of recovery, recrystallization and grain growth, with the microstructure gradually changing from a fibrous to recrystallized structure, and the secondary phases, such as the Nb(C, N) phase, σ phase and Laves phase, precipitate. In terms of mechanical properties, the tensile strength, yield strength and Vickers hardness gradually decrease, while the elongation after fracture gradually increases. When the annealing temperature reaches 800 °C, the material exhibits the optimal comprehensive mechanical properties. The yield strength, tensile strength and elongation reach 371 MPa, 534 MPa and 31%, respectively, and the hardness is 175 HV. The fracture mode of the sample is mainly ductile fracture. EBSD analysis indicates that the strong Brass {110}<112> texture existing in the cold-rolled state gradually weakens with the annealing process, and the {111}<110> texture strengthens, thereby reducing the influence of unfavorable textures. The research results provide theoretical basis and data support for microstructure regulation and performance optimization of 442 ferritic stainless steel. Full article

To clarify the influence of gouge-induced altered layers on fracture initiation and load-bearing capacity of pipelines, X70 pipeline steel is taken as the research object. The geometry and partition of the altered layer are first determined by means of a micro-Vickers hardness array and a threshold criterion, and its mechanical parameters are then obtained from small-scale tensile tests. The altered layer is subsequently embedded into a finite element model of a gouged pipe as an independent material domain, and the Gurson–Tvergaard–Needleman (GTN) damage model is employed to simulate damage evolution and crack propagation under pure internal pressure and combined internal pressure and tensile loading. The results indicate that, compared with the base metal, the yield strength and ultimate tensile strength of the altered layer increase by about 39% and 47%, respectively, while the elongation to failure decreases from 16% to 1.8%, exhibiting a typical “high-strength–low-ductility” behavior. When the altered layer is considered, the fracture initiation location under pure internal pressure shifts from the base metal to the altered layer, and the burst pressure decreases from 19 MPa to 16.5 MPa. Under the combined internal pressure and tensile loading, the peak load changes little, whereas the ultimate displacement is reduced by about 26.5%, leading to a marked loss of pipeline ductility. These findings demonstrate that the gouge-induced altered layer has a significant effect on the fracture initiation pressure, failure mode, and load-bearing characteristics of gouged pipes. Modeling it as an independent material domain in finite element analysis can more realistically capture the failure behavior and safety margin of gouged pipelines, thereby providing a more reliable theoretical basis for improving integrity assessment criteria for externally damaged pipelines. Full article