Search Results (1,591)

This study evaluated the influence of scan rate (4.23 mm/s [S10] and 6.35 mm/s [S15]) on the localized corrosion and tribocorrosion behavior of a laser engineered net shaping (LENS)-produced stainless steel 316L (SS316L) in a phosphate-buffered saline (PBS) solution. Electrochemical impedance spectroscopy (EIS) was performed by applying an AC signal from 10⁵ to 10⁻² Hz and cyclic potentiodynamic polarization (CPP) was performed by sweeping from −150 mV to +1.5 V (vs. open circuit potential) and back to characterize passivation and pitting susceptibility. Potentiostatic tribocorrosion tests were conducted using a reciprocating tribometer integrated with a potentiostat to probe material response in passive and cathodic regimes. S15 exhibited manufacturing-related defects that served as preferential pit initiation sites, with pits in both S10 and S15 showing evidence of cell-interior dissolution. Electrochemical results indicated that the charge transfer resistance was reduced by 66% for S15 and that the repassivation potential decreased by 35% compared to S10. Under tribocorrosion, material degradation was dominated by mechanical wear for both samples. However, sliding significantly accelerated electrochemical dissolution in S15, with the corrosion rate affected by wear (V_c-w) increasing by 46.8%. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) of wear scars revealed plastic deformation, abrasive grooves, and bio-tribofilm formation composed primarily of phosphates. Micro-pits associated with processing defects were observed exclusively in S15. Overall, lower scan rate processing (S10) produced a more defect-resistant microstructure with improved resistance to localized corrosion and tribocorrosion in PBS. Full article

This observational study evaluated changes in selected performance parameters of 15 new high-speed dental handpieces after eight months of routine clinical use in a routine educational undergraduate environment (two 4 h daily clinical shifts, five days per week, with repeated sterilization cycles). All handpieces underwent routine cleaning, lubrication, and autoclave sterilization as instructed. The turbine components from the handpieces were disassembled and examined by stereomicroscopy before and after use, while free-running speed and friction grip force were assessed at the same intervals. Two handpieces were no longer operational at follow-up due to ball bearing failure. Paired t-test was performed for free-running speed and friction grip force. Among the remaining handpieces, statistically significant reductions were observed in both free-running speed and friction grip force (p < 0.01). Microscopic examination of the rotors revealed surface alterations consistent with corrosion and wear. Within the limitations of this study, routine clinical use over an eight-month period was associated with measurable changes in key performance characteristics of high-speed dental handpieces in educational clinical settings. Full article

As one of the most promising new materials in the field of materials science, high-entropy alloys (HEAs) have attracted widespread attention due to the unique structure, exceptional properties and engineering performance, and complex composition. The CoCrFeNiZr_0.5 eutectic high-entropy alloys (EHEAs) exhibits excellent high-temperature thermal stability, ductility, creep resistance, and corrosion resistance, demonstrating great potential for applications in marine equipment. This paper explores the engineering feasibility of electrical discharge machining (EDM) of CoCrFeNiZr_0.5 EHEAs and investigates the EDM of micro-holes using a hollow copper electrode on a CNC EDM drilling machine under various machining parameters, including different gap voltage, pulse-on time, pulse-off time, and pulse amplifier settings. The effects of these parameters on the inlet diameter, outlet diameter, and recast layer of the micro holes are analyzed. The optimal micro-hole machining parameters are determined by comprehensively considering machining efficiency and electrode wear: gap voltage of 33 V, pulse-on time of 3 μs, pulse-off time of 1 μs, and pulse amplifier output of 3 A. Adopting the parameters to process a button ingot sample with a depth of 5 mm, it was found that the machining speed is 7.79 mm/min and the electrode wear is 1 cm. This research renders the foundation for further development and engineering application of CoCrFeNiZr_0.5 EHEAs in the context of high-value material design and manufacturing. Full article

Chromium nitride (CrN) can be used as a coating material deposited via physical vapour deposition (PVD), thereby improving the corrosion and wear resistance of the substrate. However, this level of corrosion protection may not be sufficient in an aggressive corrosion environment. The coatings often contain intrinsic microstructural defects, such as microcraters, which can serve as pathways for the corrosive medium to reach the substrate, thereby initiating and promoting corrosion. In this study, the influence of parameters on the formation of a TiO₂ layer using the ALD technique was investigated. In particular, the work focused on assessing the effectiveness of the TiO₂ layer as a sealing barrier for CrN coatings (PVD) applied to austenitic 316L steel. The TiO₂ ALD coatings were produced at a constant temperature of 200 °C with a varying number of cycles, ranging from 200 to 1000 cycles. Structural investigations were carried out using scanning electron microscopy SEM and atomic force microscopy. Electrochemical properties were investigated using a potentiodynamic test and electrochemical impedance spectroscopy (EIS) in a 3.5% NaCl solution. SEM observations indicate that the morphology of the hybrid coatings is strongly influenced by the number of ALD cycles. The TiO₂ layer conformally reproduces the underlying PVD topography while progressively sealing the coating by filling intrinsic defects and discontinuities. Hybrid coatings (PVD/ALD) with titanium oxide deposited at 500 ALD cycles were found to have the best corrosion resistance. The polarisation resistance for these coatings was nearly four times higher than that of both the single PVD (CrN) coating and the uncoated stainless steel 316L substrate. At the same time, the corrosion current density was several times lower than that of the reference systems. The corrosion mechanisms were investigated by observing the surfaces of the samples after corrosion testing using SEM. Abrasion resistance tests using the pin-on-disc method and adhesion tests (scratch tests) were also performed, which showed that appropriate optimisation of the layer architecture in the PVD/ALD hybrid system significantly improves its tribological durability, interlayer stability, and adhesion to the substrate. Full article

S136 mold steel is widely used in the injection molding industry due to its excellent properties. However, during actual production, the mold is inevitably exposed to harsh service conditions involving high temperature, high pressure, chemical corrosion, and mechanical wear, leading to risks of failure caused by pitting corrosion, intergranular corrosion, electrochemical corrosion, selective dissolution, and surface fatigue wear. To enhance the surface protection performance of the mold, a TiC-reinforced 440C stainless steel composite coating was fabricated on the S136 substrate using plasma spray welding technology. Composite powders with different TiC contents (wt.%) were prepared via mechanical mixing. The phase composition, microstructure, microhardness, corrosion resistance, and wear resistance of the coatings were characterized by XRD, SEM, Vickers microhardness tester, electrochemical workstation, and vertical universal friction and wear tester. Furthermore, the corresponding strengthening mechanisms were elucidated. The results show that the incorporation of TiC refines the microstructure and synergistically enhances both corrosion and wear resistance. Among the tested coatings, the one with 1.0 wt.% TiC exhibits the best overall performance, with a significantly increased microhardness of 858.85 HV (approximately 1.5 times that of the substrate), an Ecorr of –0.286 ± 0.002 V, an Icorr of 4.51 × 10⁻⁷ A·cm⁻², and a friction coefficient of 0.591. This study provides important theoretical and technological insights for the surface strengthening of S136 mold steel using plasma spray welding of TiC/440C composite coatings to improve corrosion and wear resistance and extend service life. Full article

The performance requirements of wear-resistant and anti-corrosion coatings for marine equipment continue to increase. Diamond-like carbon (DLC) film has become a preferred protective material due to its high hardness, low friction and chemical inertia. To reveal the tribocorrosion mechanism of Si-doped DLC films in a seawater environment, a Cr-WC-WC/C transition layer and DLC-Si films with different Si contents were prepared by high-power pulsed magnetron sputtering (HiPIMS) technology on 304 stainless steel. The tribocorrosion tests were carried out under open-circuit potential and dynamic polarization conditions in seawater. The results show that Si doping improved the tribocorrosion resistance of the films. The sample with Si content of 9.26 at.% has the lowest self-corrosion current density, the smallest volume loss, complete wear scar morphology and no obvious substrate exposure. The strengthening mechanism is attributed to Si doping, which induces the formation of a SiO_x passivation film and a hydrated silica gel lubrication layer. This establishes a synergistic solid-chemical lubrication system, inhibits sp² cluster growth, prolongs the diffusion path of corrosive media, and mitigates the damaging wear–corrosion synergy. This study confirms that moderate Si doping can significantly improve the wear resistance and corrosion resistance of DLC films in a seawater environment, and provides a theoretical basis for the design and application of carbon-based protective coatings for marine equipment. Full article

The microstructure of high-strength martensitic steel specifically made for additive manufacturing was modified via in situ plasma arc remelting (PAR) to improve its surface properties. The results reveal that the microstructure is characterized by the intragranular martensite and intergranular eutectic structure of high-strength martensitic steel. The intragranular worm-like δ-ferrite embedding in the martensite matrix was clearly observed after PAR. Compared with the as-deposited part, the tensile strength of the PAR part reached 1753 MPa, and the ductility increased to 2.3%. The strength and elongation had increased by 20% and 229%, respectively. After in situ PAR, the wear loss decreased to 80% of the tailored high-strength martensitic steel, and the corrosion current density decreased to 17%. Both the as-deposited part and the PAR part exhibited significant intergranular corrosion morphological characteristics. Full article

The promising potential of porous metallic materials for railway applications (e.g., conductive materials, materials for braking systems) is due to their unique combination of low density, high specific surface area, and high energy absorption capabilities. Porous multi-phase silicide coatings (FeSi, Si₂CN₄) provide a synergistic effect, doubling surface hardness and establishing a stable diffusion barrier. The article proposes a comprehensive approach to replacing materials for critical railway transport components, involving the development of a base material and a barrier coating. The use of widely available induction-melting components to produce a base material with superior mechanical properties is demonstrated. The material exhibits high static strength and hardness while maintaining acceptable impact toughness and ductility. To enhance wear, corrosion, and scale resistance, technology for forming a barrier layer via silicide coatings is proposed. The coating formation technology enables the regulation of porosity through the formation of nitrogen-containing phases. It is shown that pores can serve as “containers” for fillers that impart functional properties to the coatings (e.g., adjusting the friction coefficient or electrical conductivity). The new base material–barrier coating system can serve as a foundation for the sustainable production of critical rolling stock parts and other devices for railway transportation systems. Full article

CoCrMo alloys are widely used as orthopedic and dental implants, owing to their superior mechanical properties, wear resistance, and biocompatibility. Copper (Cu) ion exhibits strong antibacterial activity, making it a promising alloying element. A systematic study was conducted on the corrosion resistance and ion release behavior of CoCrMo-xCu (Co-xCu) alloys in both as-cast and heat-treated states in different simulated solutions. The results indicated that the corrosion resistance of Co-xCu alloys decreased with the increasing Cu content, which was mainly attributed to the formation of micro-galvanic couples between the alloy matrix and Cu-rich phases. The synergistic effect of heat treatment and an appropriate Cu content can effectively improve the corrosion resistance of the alloys, and the corrosion current density (i_corr) of Cu-containing cobalt alloys was comparable to that of Cu-free cobalt alloys. Maximum concentrations of Co, Cr, and Cu ions released from Co-xCu alloys were lower than the corresponding recommended safety limits. Through the combined optimization of Cu content and heat treatment, the metal ion release levels of Cu-containing cobalt alloys can be reduced to values even lower than those of Cu-free cobalt alloys. Full article

Diamond-like carbon (DLC) coatings are increasingly explored as a practical route to enhance the surface performance of biomedical implants and tissue engineering scaffolds, particularly when combined with additive manufacturing. Rather than serving only as protective layers, DLC coatings allow for independent tuning of surface properties without modifying the bulk structure, which is especially relevant for complex 3D-printed components. This flexibility is often what makes them attractive for biomedical design. This review is structured around two main application areas: DLC coatings for prosthetic implants and DLC coatings for tissue engineering scaffolds. Within this context, the influence of DLC structure (e.g., sp²/sp³ bonding, hydrogen content, and doping) on mechanical, tribological, and biological behavior is discussed. Particular attention is given to additively manufactured metallic implants and porous scaffolds, where large surface area and internal architectures complicate coating uniformity and adhesion. Reports show that DLC coatings can improve corrosion resistance, reduce wear, and influence biological responses, such as antibacterial activity and cell interactions. Several challenges remain to be solved, especially in achieving uniform coating penetration in porous networks and in ensuring long-term stability under physiological conditions. The combination of additive manufacturing and DLC coatings has been shown to offer the potential to become an enabling technology for next-generation biomedical devices. Full article

In marine service environments, material surfaces inevitably suffer from wear damage, which can compromise the integrity of protective coatings and further affect their corrosion resistance. Therefore, investigating the post-wear corrosion resistance of coatings is of great significance. In this work, single-layer CrN coatings, CrAlN coatings, and CrN/CrAlN multilayer coatings were deposited on stainless-steel substrates by arc ion plating, and the microstructure, tribological properties, and corrosion behavior before and after wear were systematically investigated. Wear tests were performed under applied loads of 2.5 N and 5 N. The corrosion behavior in the unworn condition and the post-wear corrosion resistance condition was evaluated in a 3.5 wt.% NaCl solution. The results showed that all coatings exhibited a face-centered cubic (FCC) structure, while the CrN/CrAlN multilayer coating possessed the smallest average grain size (13.47 nm). Under applied loads of 2.5 N and 5 N, the CrN/CrAlN multilayer coating exhibited the lowest wear rate, indicating the best wear resistance. In the unworn condition, the CrN/CrAlN multilayer coating showed the lowest corrosion current density (2.74 × 10⁻¹⁰ A/cm²) and the most positive corrosion potential (0.025 V), demonstrating the best corrosion resistance. After wear under a load of 5 N, the CrN/CrAlN multilayer coating retained a low corrosion current density (3.35 × 10⁻¹⁰ A/cm²), in contrast to the marked increases observed for the single-layer coatings. The enhanced performance is considered to be mainly associated with the periodic heterogeneous interfaces in the multilayer structure, which help suppress crack propagation and prolong the penetration path of corrosive media. Full article

This study investigates how cooking oil-based cutting fluids (CKO-CFs) perform as sustainable alternatives to conventional mineral oil-based fluids when turning AISI 1020 mild steel. Waste cooking oil was cleaned, treated, and mixed with selected additives to improve stability, lubricity, and corrosion resistance. Machining experiments were designed using the Taguchi L9 orthogonal array to optimise cutting speed, feed rate, and depth of cut. The CKO-based cutting fluid showed lower surface roughness at 0.270 μm compared to conventional cutting fluids at 0.274 μm. This indicates better lubricity and a smoother surface finish. Tool-tip temperatures were reduced by up to 11.99% compared to conventional fluids. This improves heat dissipation and lowers thermal damage. Tool wear was reduced by up to 5.75% with the CKO-based fluid, suggesting better lubrication and a longer tool life than conventional cutting fluids. The findings show that CKO-based cutting fluids provide an eco-friendly and efficient option for sustainable machining operations. Full article

High-power impulse magnetron sputtering (HiPIMS) technology was used to deposit Ti-Nb-Cr films on Si (100) and 316L substrates by changing the peak power of the Ti-Nb-Cr target. Optical emission spectroscopy (OES) was used to study the effect of peak power on the ion atomic arrival ratio in front of the substrate. Experimental instruments such as an X-ray diffraction (XRD) device, scanning electron microscope (SEM), transmission electron microscope (TEM), nanohardness tester, ball-disk reciprocating friction machine, and electrochemical workstation were used to study the effects of the atomic arrival ratio of Ti, Nb, and Cr ions on the microstructure, mechanical properties, and corrosion resistance of Ti-Nb-Cr films. The results show that when the peak power is 67.84 kW, the ion atomic arrival ratio of Ti reaches 47.57%, the ion atomic arrival ratio of Nb reaches 39.41%, and the ion atomic arrival ratio of Cr reaches 10.6%. The ion atomic arrival ratio is doubled compared to the peak power of 51.04 kW. The films prepared at different peak powers all show diffraction peaks of the BCC structure. At high power levels, the TiNbCr films exhibit reduced residual compressive stress, although this may be accompanied by lower hardness and wear resistance. Full article

Ceramics are widely evaluated for their extreme hardness, high-temperature stability, and corrosion resistance, which enable applications in harsh service environments. However, these same properties, high melting points, brittleness, and low thermal shock resistance, make conventional manufacturing of complex ceramic components difficult and expensive. Traditional processes often require costly diamond tooling or energy-intensive sintering and tend to produce only simple geometries, with significant waste material and risk of defects. Additive manufacturing (AM) has recently emerged as a promising route to fabricate intricate, near-net-shape ceramic parts without these drawbacks. By building components layer by layer, AM reduces the need for extensive machining and enables the fabrication of geometrically complex, near-net-shape ceramic structures with reduced material waste, although challenges such as porosity, interlayer defects, and cracking during post-processing remain. Nonetheless, ceramic AM technologies lag behind their metal and polymer counterparts, and significant challenges remain in achieving fully dense parts with reliable mechanical properties. This review provides an in-depth overview of the state of the art in ceramics and ceramic composite additive manufacturing. We detail the most widely used AM processes (stereolithography, binder jetting, material extrusion, powder bed fusion, inkjet printing, and direct energy deposition) and typical feedstock formulations for each technique. We examine the resulting mechanical properties (strength, toughness, hardness, wear resistance) and functional properties (thermal stability, dielectric behavior, biocompatibility) of additively manufactured ceramics, and discuss their current and potential engineering applications in the aerospace, defense, automotive, biomedical, and energy sectors. Persistent challenges, including porosity, shrinkage and cracking during sintering, achieving uniform microstructures, high process costs, and scalability issues, are analyzed, and we highlight promising future directions such as multi-material grading, integration of machine learning for process optimization, and sustainable manufacturing approaches. Despite significant progress, challenges remain in achieving fully dense structures, improving process reliability, and scaling ceramic AM for industrial applications, highlighting the need for further research in process optimization, material design, and multi-material integration. Full article