Alloy Substrate Research Articles

Mg-Doped Carbonated Hydroxyapatite and Tricalcium Phosphate Anodized Coatings on Titanium Implant Alloys

The rising demand for dental and orthopedic implants and their frequent aseptic loosening failure mode necessitate the drive to continue modifying implant surfaces to improve osseointegration outcomes. Plasma-sprayed hydroxyapatite coatings are widely used but are prone to delamination. This study involves a single-step anodization process utilizing a novel electrolyte to produce Mg-doped carbonated hydroxyapatite and tricalcium phosphate-containing coatings on four titanium alloy surfaces. XRD confirmed hydroxyapatite and tricalcium phosphate formation, with FTIR examination revealing carbonate substitutions indicative of bone-like apatite formation in each oxide. SEM analyses revealed micro- and nano-scaled surface features on each oxide. SEM and EDS analyses of the oxide coating cross-sections showed each group to be bi-layered with an inner titanium dioxide-rich layer and an outer hydroxyapatite/tricalcium phosphate-rich layer. The oxide layer adhesion quality was shown to be good on CPTi, TAV, and TiMo α + β implant alloy surfaces. Unfortunately, the anodization process also resulted in an undesirable and embrittling omega phase at the substrate–oxide interface due to the migration of molybdenum into the inner oxide. Nonetheless, the anodized coatings on the CPTi and TAV alloy substrates, which are the most widely used titanium alloys for implant applications, show much potential for improving future patient outcomes.

Expanding the Applications of Copper-based Alloys by Thermal Arc Spraying

In this article, the case of depositing a Ni-based alloy layer by thermal arc spraying on a copper alloy substrate with cylindrical geometry over its entire surface is presented. After the coating was deposited, the layer was analyzed microstructurally both on the surface and in cross-section, and it was observed that it adhered very well to the substrate. In addition to the high adhesion to the substrate, a low porosity of the coating was observed, which ensures good compactness of the coating. Based on these results, further investigation of the Ni coating can be recommended to limit the toxicity caused by the oxidation of copper and copper alloy heating elements.

Silver Linings: Electrochemical Characterization of TiO2 Sol-Gel Coating on Ti6Al4V with AgNO3 for Antibacterial Excellence

This study aimed to synthesize TiO2 and silver-containing TiO2 layers on Ti6Al4V titanium alloy substrates, also known as titanium grade 5 (TiGr5), to provide corrosion resistance and antibacterial activity. The TiO2 layers were prepared through the sol-gel method and dip-coating technique. Silver introduction into the layers was performed in two different ways. One was the impregnation method by dipping the TiO2 layer-covered metal in aqueous AgNO3 solutions of various concentrations (TiO2/AgNO3), and the other was by direct introduction of AgNO3 into the precursor sol (Ag-TiO2). The two methods for incorporating AgNO3 into the coating matrix are novel, as they preserve silver in its ionic form rather than reducing it to metallic silver. The samples were put through electrochemical characterization, namely potentiodynamic polarization and electrochemical impedance spectroscopy (EIS), and were tested in Hank’s solution, simulating a physiological environment. The behavior of the layers was monitored over time. Also, the thin layers’ thickness and adhesion to the substrate were determined. Microbiological evaluation of the Ag-doped coatings on glass substrates confirmed their significant bactericidal activity against Gram-negative Escherichia coli. Among the two types of coatings, the impregnated coatings demonstrated the most promising electrochemical performance, as evidenced by both EIS and potentiodynamic polarization analyses.

Waterborne superhydrophobic bio-epoxy coating on Al alloy for corrosion-resistant and self-cleaning applications

Aluminum (Al) and its alloys are important engineering materials in modern industry due to their numerous advantages and have been widely used in various fields, including aerospace, marine, civilian industries and so on. However, they are prone to corrosion and contamination under harsh environmental conditions, particularly in marine environment when exposed to salty water or moisture for a long time, which can adversely affect their aesthetic appearance and desired functionalities or even cause economic losses and serious accidents. To prevent or delay the corrosion, the hydrophilic nature of Al and its alloy surfaces can be transformed to be hydrophobic or superhydrophobic. In this study, we reported an environment-friendly waterborne superhydrophobic bio-epoxy coating (WSBC) without using volatile solvents. The coating is composed of bio-epoxy resin, nano silica, silane coupling agent as well as hydrophobic curing agent, and applied by spin method on Al alloy substrates. The surface morphology and roughness were characterized by a field emission scanning electron microscope (FESEM) and an atomic force microscope (AFM). The WSBC with 22.2 wt% nano silica loading without considering the solvent of DI water displays a water contact angle (CA) as high as 165.8 ± 3.3° and a sliding angle (SA) as low as 5.3 ± 2.5°. Electrochemical measurement results showed that the as-prepared WSBC has a significant shift from −1.160 V to −0.708 V in the corrosion potential (Ecorr) and 3 orders of magnitude decrease in the corrosion current density (Jcorr), indicating excellent corrosion resistance. The WSBC was further proven to function well after immersion in deionized (DI) water and common organic solvents including ethanol and acetone for 48 h, and weathering resistance test. In addition, the as-prepared WSBC also showed good self-cleaning performance. The developed coating is green and no harm to human health and environment. The facile and eco-friendly process is of great importance for many industrial applications which can provide an attractive way towards anti-wetting surfaces for corrosion protection and self-cleaning effect on a variety of engineering substrates.

Ti3C2Tx and Mo2TiC2Tx MXenes as additives in synovial fluids - towards an enhanced biotribological performance of 3D-printed implants

Synovial joints, critical for limb biomechanics, rely on sophisticated lubrication systems to minimize wear. Disruptions, whether from injury or disease, often necessitate joint replacements. While additive manufacturing offers personalized implants, ensuring wear resistance remains a challenge. This study delves into the potential of Ti3C2Tx and Mo2TiC2Tx nanosheets in mitigating wear of additively manufactured cobalt-chromium tungsten alloy substrates when incorporated as additives into synovial fluid. The colloidal solutions demonstrate an excellent stability, a crucial factor for reproducible assays and potential clinical applicability. Analysis of contact angles and surface tensions reveals MXene-induced alterations in substrate wettability, while maintaining their general hydrophilic character. Viscosity analysis indicates that MXene addition reduces the dynamic viscosity, particularly at higher concentrations above 5 mg/mL, thus enhancing dispersion and lubrication properties. Friction and wear tests demonstrate a dependency on the MXene concentration, while Ti3C2Tx exhibits stable friction coefficients and up to 77 % wear reduction at 5 mg/mL, which was attributed to the formation of a wear-protecting tribo-film (amorphous carbon and MXene nano-sheets). Our findings suggest that Ti3C2Tx, when supplied in favorable concentrations, holds promise for reducing wear in biotribological applications, offering avenues for future research into optimizing MXene utilization in load-bearing joint replacements and other biomedical devices.

Biodegradation and mechanical performance of Silane-chitosan-graphene oxide composite coating on AZ31 magnesium alloys for biomedical applications.

Biodegradable magnesium alloy medical implants have attracted considerable interest thanks to their remarkable biocompatibility and mechanical properties. However, the rapid corrosion rate of magnesium alloys in physiological environments presents a major challenge to their practical application. Therefore, this study attempted to design a silane/chitosan /graphene oxide composite coating that reduces the corrosion and enhances the biodegradation of magnesium alloys used in temporary implants. The composite fabrication process adopted a cost-effective spin-coating technique providing a uniform coating of magnesium alloy substrates. Fourier transform infrared spectroscopy (ATR-FTIR), Raman spectroscopy, scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS) results showed a dense and compact silane/chitosan/graphene oxide (Silane/CS/GO) coating on the magnesium coated alloy surface. The mechanical properties of the fabricated silane/chitosan/graphene oxide composite were also investigated by microindentation and scratch tests. The hardness of the magnesium alloy increased from ~268 HV ±13.4 to ~644.13 HV ± 32.2 upon the application of the coating. Moreover, the results showed that the cohesive critical load (LC) of the ternary composite was greater than LC ~ 3.02 ± 0.15 N. In addition, compared to uncoated AZ31 alloys, the friction coefficient and wear volume of the ternary composite decreased from ~0.13 ± 0.02 to ~0.07 ± 0.004 and from ~18 to ~0.04 (106μm3), respectively. Finally, the corrosion of the composite coating was assessed in simulated body fluid (SBF) in vitro at 37 °C. Hydrogen evolution results revealed that graphene oxide seemed to delay the diffusion of corrosive ions into the Mg matrix, while Silane prevented the coupling of GO graphene oxide sheets to the metal surface. Consequently, silane / chitosan /graphene oxide composite coatings could be a very useful material for coating magnesium implant devices. It contributed to reduce the corrosion of the substrate and alleviate the cost and discomfort of implants.

Preparation of a novel laser cladding Ni-based alloy with promising applications in high-temperature conditions: Genetic design, multi-phase evolution, and synergy mechanism

Developing novel Ni-based alloys is crucial for remanufacturing key friction parts at 800-1200 ℃ in metallurgical industry with multiple failure mechanisms, such as wear, corrosion, and adhesion. This paper adopts genetic algorithm to design high-temperature Ni-based alloy with three genetic structures of wear resistance, anti-corrosion, and self-lubricating. By combining simulation calculation and experimental methods, the evolution of the three genetic structures of the laser cladding alloy and the performance strengthening mechanism were deeply studied. The laser clad Ni17Cr10Co7Al5Ti3W2C1S sample of optimized composition had three genetic structures: Cr7C3/TiC wear resistance phases, γ/γ′ anti-oxidation and anti-corrosion phases, Ti2SC/TiS self-lubricating phases. Compared with Cr28Ni48W5 superalloy, the wear rate of the optimal sample was 2.31×10-5 mm3/(N·m) under 800 ℃ friction condition, and reduced by 97%. The friction coefficient of the sample at high temperature was 0.2, approximately half of the substrate alloy, and the self-lubricating performance was significantly improved. Electrochemical tests indicated that the polarizing potential of the sample was -0.16 VSCE in 3.5wt. % NaCl solution. The mechanism of three genetic structures evolution and synergistic enhanced wear resistance, anti-corrosion, and self-lubricating properties were elaborated. Specifically, the key gene of Ti2SC plays a profound role in improving the high-temperature wear resistance and self-lubricating performance of the novel laser clad Ni-based alloy sample. These findings present a novel avenue of material design and preparation for laser additive manufacturing and remanufacturing of key friction parts with high-performance at 800-1200 ℃ in complex metallurgical working conditions.

Formation and properties of niobium silicide coatings on Nb-Ta alloy substrate

Formation and properties of niobium silicide coatings on Nb-Ta alloy substrate

Morphology and Properties of the Laser-Irradiated Composition “Chrome Coating — Copper Substrate”

Introduction. During pulsed laser processing and modification of the surface of non-ferrous alloys and coatings based on them, several still unresolved issues arise. In particular, the extreme thermal deformation conditions of laser processing are not linked to the peculiarities of structure formation and formation of properties in irradiated “coating — copper substrate” compositions. A metal physical analysis of the possibility and reasons for increasing the adhesion strength of coatings to a metal (copper) substrate during high-speed laser processing is insufficiently substantiated and evidence-based. To make a reasonable choice of technological parameters for the surface hardening mode of non-ferrous alloy products, as well as for obtaining high-quality workable composite layers on their surface, it is necessary to solve the above issues and tasks. The aim of this article is to determine the possibility and conditions for increasing the adhesion strength of a chrome coating to a copper substrate under laser irradiation of the composition.Materials and Methods. Metal physical studies in the work were carried out on samples of non-ferrous alloys of the Cu–Zn system with a chrome electrochemical coating with a thickness of 20 μm. The “copper substrate — chrome coating” composition was irradiated at a Kvant-16 installation with a radiation power density of 70–250 MW/m2. Metallographic structural analysis, scanning probe microscopy, and durometric studies were used in the work.Results. It has been calculated that the dynamic and thermal stresses arising in the laser-irradiated compositions “chrome coating — copper substrate” were about 320 MPa. Metal physical studies revealed that, in extreme thermal deformation conditions of laser treatment, the effect of contact melting was manifested at the boundary of the coating with the copper base. Dynamic recrystallization occurred in the surface layers of the irradiated L62 copper alloy, resulting in the formation of grains with a size of 4.5–5.0 μm on the surface of the alloy with an initial grain size of 25 μm.Discussion and Conclusion. It has been found that the adhesion strength of a chrome coating to a copper alloy substrate increased laser irradiation at a radiation power density of 150 MW/m2. This was due to the formation of a transition region 2–4 μm deep in the contact zone with a structure consisting of sections of mutually insoluble solid solutions based on chromium and copper. Based on the analysis of the copper —chromium state diagram and the model of the temperature field under laser irradiation of the chromium coating, it was suggested that contact melting occurred in the transition zone from the coating to the copper substrate. It was shown that thermostrictive stresses, the calculated quantitative values of which were about 320 MPa, had an initiating effect on the observed processes of structure formation in the laser irradiation zones. It was found that such a level of stresses arising in copper alloys under laser irradiation was sufficient for plastic deformation and dynamic recrystallization of the metal and contributed to the formation of a fine-grained structure (4.5–5.0 μm) with an initial grain size of 25 μm. An analysis of the results of studies of irradiated compositions "coating — copper substrate" allowed us to conclude that they expanded the technological capabilities of the laser method of hardening materials and ensure guaranteed high performance of irradiated products with coatings

Deciphering Lithium Deposition Behavior in Elemental Alloy Anodes for Lithium Metal Batteries.

Lithium (Li) dendrite is one of the most fatal obstacles for developing practical high energy Li metal batteries, while Li alloy substrates, with strong lithiophilicity, have attracted increasing interest for directing uniform Li deposition. However, most of the previous research studies associated Li dendrite inhibition closely with high adsorption energy. Yet, the Li deposition process is not solely about the adsorption of an isolated Li atom, where a comprehensive understanding of the interfacial lattice mismatch and the Li atom diffusion should also be taken into account. Here, we explore the Li deposition behavior from adhesion work, representing interfacial stability and bonding strength, and both Li adsorption and diffusion. It is found that the overpotential of Li deposition is inversely related to adhesion work, while uniform Li deposition requires a high adsorption energy and low Li atom diffusion barrier. These detailed relationships may offer guidance for subsequent substrate development.

Performance Descriptor of Subsurface Metal-Promoted Boron Catalysts for Low-Temperature Propane Oxidative Dehydrogenation to Propylene.

Boron-based catalysts have exhibited excellent olefin selectivity in the oxidative dehydrogenation of propane (ODHP) reaction. The substrate material should be a potential platform for performance modulation of boron catalysts in this reaction since the introduction of subsurface Ni promoters significantly improves the activity. In this study, we deciphered the substrate effect and identified a performance descriptor to comprehend the roles of subsurface materials in BOx/metal/BN ODHP catalysts by evaluating different metal promoters. Performance evaluation and transient infrared spectroscopic experiments demonstrate that the intrinsic activity and kinetic behaviors of the O-H bond dissociation/regeneration on the metal-promoted BOx overlayer are metal substrate-dependent. Combining density functional theory (DFT) calculations, it is found that the dissociation/regeneration inclination of the O-H bond in BOx(OH)3-x active species is controlled by the affinity of H for boron oxide species. The metal-O binding energy, which has been demonstrated to be linearly correlated with H affinity, can serve as a straightforward performance descriptor for both low-temperature radical initialization and ODHP reaction, revealing this reaction is controlled by the Sabatier principle, and moderate metal-O binding energy is essential for achieving remarkable performance in the BOx/M/BN catalysts. Following the guidance of a potential descriptor, Ni-Rh alloy substrates are investigated and the substrate with a Ni/Rh molar ratio of 15:1 significantly enhances the low-temperature intrinsic activity of the metal-modified BOx to 9.26 μmol/(m2·s), which reaches 105.9 times that of h-BN and is 18.3% larger than the monometallic BOx/Ni/BN catalysts.

Synthesis and evaluation of tribo-mechanical and corrosion properties of electroless Ni-P coating on AZ91D Mg alloy with stannate conversion underlayer

The work reports on synthesis and comprehensive evaluation of different properties of a bilayer protective coating on Mg alloy of AZ91D grade. Initially the alloy substrates were treated in stannate bath for 15, 30, 45, 60, 75 and 90 min for synthesizing an MgSnO3.3H2O layer. Electroless Ni-P was then deposited for 30 and 60 min, on the stannate layer synthesized for 60 min. A time-dependent cyclic growth behaviour was observed for stannate layers, characterized by formation and dissolution of MgSnO3.3H2O globules. The stannate coatings displayed polycrystalline structure. Hardness and scratch resistance were strongly influenced by uniformity of the coatings. While the uncoated alloy exhibited hardness of only 93 HV0.05, a remarkable improvement in hardness to 484 HV0.05 was obtained after 60 min of stannate treatment. High critical load of adhesion (Lc3) of 29 N was also obtained for the same. The stannate layers exhibited coefficient of friction (CoF) of 0.4–0.6 as compared to 0.7–0.8 for bare alloy. The wear loss also notably reduced. In tribo-test, hard and well-adherent coating restricted surface deformation under action of normal load. This in-turn, reduced mechanical engaging at interface, leading to low CoF and wear loss. The dense stannate coating also reduced corrosion rate by 19 times by hindering penetration of corrosive medium. Electroless deposition for 30 min on stannate conversion layer yielded only sporadic growth of Ni-P, which improved to a dense, uniform layer after 60 min of deposition. The Ni-P top coating aided the stannate underlayer in furthering the tribo-mechanical and corrosion characteristics.

Growth mechanism and tribological behavior of electroless Ni-P plating with ultrasonic assistance on titanium alloy substrate

The aim of this paper is to study the growth mechanism and tribological behavior of electroless Ni-P plating with ultrasonic assistance on TC4 titanium alloy substrate pretreated by zincating and alkaline pre-plating process. The morphology, composition and structure of zincating, pre-plating and electroless Ni-P plating were studied to analyze its growth mechanism. The tribological behavior of electroless Ni-P plating at room temperature was investigated. The results showed that the electroless Ni-P plating had a typical cauliflower-like morphology and microcrystalline structure characteristic. And the morphology of the Ni-P plating under the action of ultrasonic was uniform, compact and smooth. Compared with the TC4 substrate, the friction coefficient and the wear scar width of the plating were reduced by approximately 35 and 70%, indicating that the Ni-P plating improved the wear resistance of TC4. The wear mechanism of the Ni-P plating was adhesive wear under the dominant of plastic deformation, and slightly abrasive wear, while the wear mechanism of TC4 was dominated by adhesive wear, accompanied by abrasive wear and oxidative wear. The ultrasonic cavitation promoted the elemental interdiffusion between the substrate and Ni-P plating resulting in the formation of the diffusion layer. The ultrasonic cavitation and mass transfer effects improve the activity of the deposition surface and the generation of atomic hydrogen, and promote the nucleation and growth of nickel on the deposition surface, as well as the diffusion of Ni2+ and H2PO2− to the deposition surface. The growth rate of the Ni-P cell-like structures in the parallel direction is greater than in the perpendicular direction. The Ni-P plating grows in a layered manner, and the growth mechanism is the heterogeneous nucleation growth mechanism.

Stainless Steel Deposits on an Aluminum Support Used in the Construction of Packaging and Food Transport Containers

A series of chemical elements from the chemical composition of the packs of liquid food products migrate inside them or they combine with other chemical elements existing in the food, resulting in chemical compounds that worsen the quality of the food. In the present paper, layers of food stainless steel were deposited using thermal arc spraying on an aluminum alloy substrate to stop the migration of aluminum ions inside liquid food products. The physical-chemical and mechanical properties of the protection system: stainless steel layer used in the food industry (suggestively called: food-grade stainless steel)—aluminum substrate were investigated, and then the organoleptic properties of the food liquids that came into contact with the deposit were evaluated. It was found that food-gradestainless steel deposits have low porosity (3.8%) and relatively high adhesion and hardness, which allows complete isolation of the substrate material. The investigations carried out on the properties of food liquids that come into contact with the stainless steel deposit revealed the fact that it perfectly seals the aluminum start. The food-grade stainless steel coating (80T) was much better and safer for preserving dairy products maintaining a constant acidity up to 17 degrees Thorner, wines (with an average acidity of 3.5–4 degrees), juices (with natural pigments), and oils (with a good absorbance level correlated with clarity). This aspect suggests that the created system can be successfully used to manufacture containers for the transport of liquid products.

Strong Bonding of Robust Lubricating Hydrogels to Porous Substrates for Joint Replacement.

Hydrogels with excellent mechanical and lubrication properties have been developed rapidly, laying the foundation for their application in cartilage replacement. However, the combination of robust hydrogels and substrates under different forms of movement is a great challenge. In addition, due to differences in modulus, the stress shielding effect caused by implantable artificial joint metal materials can lead to bone resorption. Here, we proposed to combine a 3D printed porous titanium alloy with a high-strength lubricating hydrogel to construct an integrated joint substitute material. The porous titanium alloy TC4 substrate constructed by 3D printing possesses a modulus similar to that of human bone. The strong bonding of the hydrogel and TC4 was achieved through two strategies: mechanical interlocking and chemical bonding. The combination of the alloy substrate and hydrogel realizes the construction of a bionic lubricating cartilage layer on the surface of traditional artificial joint materials. The hydrogel has excellent bonding properties with the porous substrate under different test conditions. Truly human-like joint sockets were prepared for the first time with soft-soft and soft-hard contact modes. Under conditions simulating human motion, the hydrogel maintains a low friction coefficient and still has excellent substrate adhesion after 100,000 cycles. This study further pushes the application of hydrogels in biolubrication into practice.

The Anti/Deicing Performance of the Low Interfacial Toughness Coating Is Enhanced: Induced Ice Crack Generation and Its Extension.

The low interfacial toughness of the material surface is important for crack initiation and expansion of the ice layer as it remains an effective method for large-scale deicing. However, there are challenges, such as a large critical icing size and incomplete shedding of the ice layer. Adjusting the interfacial forces to make the ice more prone to cracking, expanding, and shedding is advantageous in addressing the problem of anti-icing failure in materials with low interfacial toughness. Therefore, we propose a deicing strategy that combines porous PDMS (polydimethylsiloxane) coatings with low interfacial toughness and piezoelectric vibration. A series of hydrophobic porous PDMS coatings with different porosities were prepared on the surface of an aluminum alloy substrate through curing and phase separation. The elastic modulus of the coatings decreased from 1465 to 509 kPa as the coating porosity increased, revealing the mechanism behind the improvement in mechanical properties. The key to promoting ice fracture on porous PDMS coatings lies in the synergistic effect of the out-of-plane shear stress and microcracks at the solid-ice interface. This work focuses on exploring the characteristics of interfacial forces by combining the intrinsic mechanical properties of coatings with external forces, providing new insights for designing low interfacial toughness anti-icing materials.

Effect of elevated temperature on the bond behaviour of adhesive shear joints between glass substrate and iron-based shape memory alloy strip

Glass has been increasingly used as structural elements, such as glass beams or fins. Previous feasibility studies have shown increased initial and post-fracture load-bearing capacity of laminated glass beams post-tensioned with adhesively bonded iron-based shape memory alloy (Fe-SMA) strips. However, the potential elevated service temperatures were not considered, which significantly degraded the material properties of the adhesive. This study experimentally investigated the mechanical behaviour of Fe-SMA-to-glass lap-shear joints with an epoxy adhesive at different temperatures of 23 °C, 50 °C, and 80 °C, representing room temperature and typical elevated service temperatures. The results showed that, compared with the one at room temperature, the load-carrying capacity remained nearly unchanged at 50 °C and decreased by approximately 20 % at 80 °C. On the contrary, the effective bond length increased from approximately 116 mm to 250–300 mm. The failure modes, the tensile strain of the iron-based shape memory alloy, the bond-slip behaviour, and the fracture energy of the joints were also evaluated. The current study fills a significant research gap in the engineering application of strengthening glass structures by bonded pre-stressed Fe-SMA strips. Moreover, the results may also significantly contribute to the future application of the selected adhesive at elevated temperatures.

Corrosion-oriented self-healing coating based on ZnMg MOF for efficient corrosion protection of aluminum alloy via in-situ LDH film formation

A corrosion-oriented self-healing coating system relying on metal–organic framework (MOF) based nanofiller is designed for aluminum alloy protection. The nanofiller is comprise of ZnMg MOF nanoparticle as a framework, salicylaldoxime corrosion inhibitors inside the MOF, and a polydopamine layer on the MOF surface. The Al3+ ions generated from the aluminum alloy substrate at the damaged coating area can etch the nanofiller, causing the collapse of the nanofiller and releasing the corrosion inhibitors to suppress the corrosion process in time. Subsequently, Zn2+ and Mg2+ ions from the nanofiller co-precipitate with Al3+ to form a dense AlZnMg layered double hydroxide (LDH) film, which provides further protection performance at the exposed alloy surface. Electrochemical impedance spectroscopy results demonstrate that the intact MOF@S/P coating exhibits a remarkable corrosion resistance property. For the damaged coating, the self-healing performance originated from the formation of LDH layer and the release of corrosion inhibitors gradually took effect, with the |Z|0.01Hz value increasing 2.27 times within 14 days. Moreover, under near-infrared irradiation, the photothermal effect of polydopamine will accelerate the release of corrosion inhibitor, the formation of LDH film, as well as the shape memory effect of coating defect for an efficient recovery of the corrosion resistance property. This novel coating system enables a corrosion-driven and location-specific repair with in-situ deposition of both an inhibitor film and an LDH film. As the first work to fully utilize and consume nanofillers on demand, this approach prevents inadequate use of healing agents, addressing a significant challenge in corrosion-driven self-healing coatings. The self-healing mechanism ensures target-oriented corrosion protection that makes the most efficient use of the healing substances.

Analysis of the Ni-5%at.W Alloy Substrate Texture Evolution at Different Strain Levels Using the EBSD Technique.

In this paper, the texture evolution of the Ni-5%W alloy baseband with different strain variables (εvM = 3.9, 4.9, and 5.1) during rolling and annealing was studied using the electron back scattering diffraction (EBSD) technique. The results indicate that after high-temperature annealing at 1150 °C, all three strain levels of the alloy substrates can achieve a strong cubic texture, with a content exceeding 99% (<10°). However, the texture evolution trajectory is significantly influenced by the strain level. When the content of cubic texture in the alloy substrates under strain levels of 3.9 and 5.1 is the same, significant temperature differences exist. Additionally, the different strain levels result in varying nucleation rates and growth rates of cubic texture in the Ni-5%W alloy substrates. The study reveals that in the alloy substrates under strain levels of 3.9 and 4.9, recrystallized cubic grain nuclei grow within a layered structure, resulting in larger grain sizes and lower nucleation rates. In contrast, in the alloy substrates under a strain level of 5.1, recrystallized cubic grain nuclei form from small equiaxed grains, leading to higher nucleation rates but smaller grain sizes, competing with random orientations. In the later stages of nucleation, recrystallized grains in the alloy substrates under a strain level of 5.1 exhibit a significant size advantage, rapidly growing by engulfing randomly oriented grains. Compared to the alloy substrates with lower strain levels, the recrystallized cubic grains in the alloy substrates under a strain level of 5.1 have higher nucleation rates and faster growth rates.

Corrosion mechanisms of plasma sprayed porous coatings of Ni80Cr20 and alloy C-276 investigated by numerical and experimental method

Abstract: In this study, the corrosion performance of Ni80Cr20 and alloy C-276 (UNS N10276) coatings on 7075 aluminum alloy substrates was evaluated using a variety of performance characterization tests. Significant amounts of nickel oxide were found in the corrosion products of the two coatings that were stripped, with molybdenum in the two coatings that were not stripped effectively slowing down the corrosion rate. Both coatings selectively corrode Cr, where it is worth noting that the preferential corrosion of W elements in alloy C-276 has a positive effect on its surface protection. It is not only the amount of molybdenum content, but also the influence of the W element that leads to better corrosion resistance of alloy C-276 coating than Ni80Cr20 alloy coating. The coating spraying process due to process parameters and its own nature, etc. has caused different sizes of pores, while these pores in the corrosion process will have a certain degree of influence on the corrosion process. The size of the pore defects for the coating transverse corrosion effect was more significant, and small pore defects accelerated the corrosion process. The number of pore defects had a more significant effect on the longitudinal corrosion of the coating, and multiple pore defects slowed the corrosion process.