Titanium Alloy Substrate Research Articles

Cultivating a comprehensive understanding of microstructural attributes and wear mechanisms in FeCrCoNiAlTix high-entropy alloy coatings on TC6 substrates through laser cladding fabrication

Titanium effectively improves the hardness of FeCrCoNiAl high-entropy alloy (HEA) coatings. In this study, FeCrCoNiAlTix (x = 0, 0.3, 0.5, 0.8, and 1.0) high-entropy alloy coatings were successfully prepared on TC6 titanium alloy substrates via laser cladding(LC). Through the preparation of LC, the effects on the microstructure, phase composition and fretting wear behavior of coatings with different Ti molar ratios were investigated in detail. The results showed that the FeCrCoNiAlTix (x = 0, 0.3) HEA coatings consisted of face-centered cubic (FCC) and body-centered cubic (BCC) phases. With increasing Ti content of the FeCrCoNiAlTix (x = 0.5, 0.8, and 1.0) HEA coatings, a new eutectic BCC2 hard phase appeared. The FCC phase was the continuous in the microstructure, whereas the BCC and BCC2 phases formed a hard skeleton. The hardness of the FeCrCoNiAlTix HEA coatings increased with increasing Ti content, and the hardness of the Ti1.0 HEA coating reached a maximum of 848 HV0.1. The FeCrCoNiAlTix (x = 0,0.3,0.5,0.8, and 1.0) HEA coatings effectively improved the resistance of TC6 alloys to fretting by fatigue, oxidative, adhesive, and abrasive wear.

Microstructures and properties of FeCrAlMoSix high entropy alloy coatings prepared by laser cladding on a titanium alloy substrate

By laser cladding, a FeCrAlMoSix high entropy alloy (HEA) coating (x = 0, 0.05, and 0.10) was produced on Ti6Al4V titanium alloy surface to improve its resistance to the influence of high-temperature fretting wear on Ti6Al4V. The mechanical characteristics, phase composition, and fretting wear resistance of the coating were examined at RT and 400 °C. The findings show that the FeCrAlMoSix coating is made up of a B2 phase and an intermetallic compound μ phase. At RT and 400 °C, increasing the Si concentration significantly enhanced the coating's microhardness. At x = 0.10, the average microhardness of the coated surface was 805 HV, and grain refinement and increase in μ phase were the reasons for the improvement of microhardness. The fretting wear experiment shows that the coating system can reduce wear loss and COF. In addition, at RT and high temperature, increasing the Si element can considerably improve the coating's resistance to fretting wear. However, due to stress concentration, too much μ phase may increase the risk of microcracking in the coating. This work provides a potential method for improving the protection against fretting wear damage on the titanium alloys' surface.

Properties of biodegradable polymer coatings with hydroxyapatite on a titanium alloy substrate.

Purpose: Titanium alloys are among the most widely used materials in medicine, especially in orthopedics. However, their use requires the application of an appropriate surface modification method to improve their properties. Such methods include anodic oxidation and the application of polymer coatings, which limit the release of alloying element ions. In addition, biodegradable polymer coatings can serve as a carrier for drugs and other substances. The paper presents the results of research on the physical properties of biodegradable polymer coatings containing nanoparticle hydroxyapatite on a titanium alloy substrate. Methods: A PLGA coating was used in the tests. The coatings on the substrate of the anodized Ti6Al7Nb alloy were applied by ultrasonic spray coating. The tests were carried out for coatings with various hydroxyapatite content (5, 10, 15, 20%) and thickness resulting from the number of layers applied (5, 10, 15 layers). The scope of the research included microscopic observations using scanning electron microscopy, topography tests with optical profilometry, structural studies using X-ray diffraction, as well as wettability and adhesion tests. Results: The results shows that with the use of ultrasonic spray coating system is possible to obtain the continuous coatings containing hydroxyapaptite. Conclusions: The properties of the coating can be controlled by changing the percentage of hydroxyapatite and the number of layers of which the coating is composed.

Effects of Pulsed Current on the Microstructure and Properties of Laser Cladded TC17 Titanium Alloy.

In this study, a titanium alloy substrate was cladded with TC17 titanium alloy powder using the pulsed-current (PC)-assisted laser cladding technique. The primary objective of this research was to assess the impact of varying pulsed current intensities on the morphology, microstructure, and properties of samples. It is observed that the utilization of pulsed currents significantly enhances the metallurgical adhesion between the samples, concurrently diminishing the occurrence of porosity within the cladding layer. The incorporation of a pulsed current also has a positive impact on the microhardness and corrosion resistance of the samples. Furthermore, the synergistic influence of laser energy and a pulsed electrical current is found to promote a structural evolution in materials towards a state with lower electrical resistance. The introduction of a pulsed current leads to preferential growth of β grains with <100>// cladding direction in the cladding zone and obtains the typical {100} < 001 > cube texture, while the substrate zone exhibits a distinctive stripe-like configuration formed by the primary α-phase constituents. The outcomes of this study show the pivotal role of pulsed currents as an auxiliary technique for enhancing the properties and effecting microstructural modifications in titanium alloys during the laser cladding process.

Microstructural Modification of Cold-Sprayed Ti-Cr3C2 Composite Coating by Laser Remelting

Laser processing is an effective post-treatment method for modifying the structure and improving the properties of cold-sprayed coatings. In the present work, the possibility of fabricating a hard and wear-resistant Ti-based cermet coating by cold spray followed by laser remelting was studied. A mixture of titanium and chromium carbide powders in a ratio of 60/40 wt.% was deposited by cold spray onto a titanium alloy substrate, which ensured the formation of a composite coating with a residual chromium carbide content of about 12–13 wt.%. The optimal values of laser beam power (2 kW) and scanning speed (75 mm/s) leading to the qualitative fusion of the coating with the substrate with minimal porosity and absence of defects were revealed. The microstructure and phase composition of as-sprayed and remelted coatings were examined with SEM, EDS and XRD analysis. It was shown that the phase composition of the as-sprayed coating did not change compared to the feedstock mixture, while the remelted coating was transformed into a β-Ti(Cr) solid solution with uniformly distributed nonstoichiometric TiCx particles. Due to the change in microstructure and phase composition, the remelted coating was characterized by an attractive combination of higher microhardness (437 HV0.1) and lower specific wear rate (0.25 × 10−3 mm3/N × m) under dry sliding wear conditions compared to the as-sprayed coating and substrate. Laser remelting of the coating resulted in a change in the dominant wear mechanism from oxidative–abrasive to oxidative–adhesive with delamination.

Optimization of cold spray process parameters to maximize adhesion and deposition efficiency of Ni+Al2O3 coatings

The paper considers the conducted study of the complex effect of low-pressure cold spraying parameters, namely the nozzle inlet temperature, stand-off distance, and powder feed rate on the adhesion and deposition efficiency of coatings from a Ni+Al2O3 powder on VT3-1 titanium alloy substrate. Based on predetermined information, the main levels and intervals of factor variation were selected. The dependence of the adhesion and deposition efficiency on the selected variables was approximated by a second-order polynomial. In accordance with the developed matrix of the experiment (central compositional design), a coating of the studied powder was deposited. The average value of these parameters was determined using standard methods for studying the adhesion strength (ASTM C603) and the deposition efficiency for thermal spray coatings. Based on the results of experimental data, regression equations were obtained for adhesion and deposition efficiency. For the purpose of checking the adequacy of the model, an analysis of variance was performed. It was confirmed that the obtained empirical dependences can be used to predict the adhesion and deposition efficiency of cold spraying of coatings from a Ni+Al2O3 powder on VT3-1 titanium alloy in the specified ranges of values of spraying parameters. Multi-factor optimization of the spraying parameters in order to obtain maximum values of adhesion strength and deposition efficiency was performed using the response surface methodology in the Stat-Ease 360 software. Three-dimensional and contour graphs of the dependence of the adhesion and deposition efficiency on the studied parameters were developed from the obtained empirical models. The optimal combination of parameters of low-pressure cold spraying, which ensures the maximum adhesion (34.78 MPa) and deposition efficiency (29.46%) of the Ni+Al2O3 coating mixture, is the nozzle inlet temperature—537 °C, stand-off distance—11 mm, and powder feed rate—0.6 g s−1.

Plasma-sprayed coatings of 62W bioactive glass: Mechanical properties and in vitro behavior

Bioactive glasses, due to their chemical and biological properties, are promising materials for being used in orthopedic applications. In this study, coatings of the novel 62W glass, with a composition in the system SiO2-CaO-P2O5-MgO, were analyzed. The 62W feedstock powder was prepared from a mixture of reagents by the melt-quenching route and deposited onto titanium alloy substrates by atmospheric plasma spray (APS) technique. The cross-section and the phase of the coatings were analyzed by scanning electron microscopy and X-ray diffraction. Mechanical and in vitro tests were conducted on the obtained coatings to evaluate their bioactive ability. The results of the cross-sections show dense coatings with the absence of the characteristic pores that appear when spraying the usual bioactive glasses. The obtained coatings present a bond strength of 32 ± 3 MPa with the substrate without crystalline phases on the microstructure. The presence of magnesium oxide in the composition favours the glass's processing and increases its crystallization temperature and, thus, the proper stacking of the deposited particles. The bioactive capacity of the 62W coatings was demonstrated at short periods after in vitro evaluation in SBF and TRIS/HCl solutions. The study reveals the potential use of 62W glass coatings for bone implant applications.

Development of Multicomponent Nanostructured Nitride Coatings to Protect against Corrosion Products from Titanium Alloy

Phase-structural characteristics and the corrosion resistance of coatings ZrN, (Zr,Ti)N, (Zr,Hf)N, (Zr,Nb)N, (Ti,Zr,Hf)N and (Ti,Zr,Nb)N, which were deposited on a Ti6Al-4V titanium alloy substrate, were investigated. It was found that the titanium substrate has a crystalline structure, including grains with high (up to 24 at.%) and low (less than 2 at.%) vanadium content. Thus, during the deposition process, the coating can form adhesive bonds with local areas of the substrate that have quite different compositions. The diffusion of the coating elements into the substrate takes place up to a depth of 200 nm. The diffusion of titanium alloy elements (primarily titanium and vanadium) into the adhesive sublayer of the coating to a depth of 100 nm is also observed. Corrosion studies were carried out in 1M solutions with acidic (H2SO4), alkaline (NaOH) and neutral (NaCl) media at a constant temperature of 50 °C. The actual change in the mass of the samples during corrosion tests is extremely small. The protective coatings under study have very high anti-corrosion characteristics and practically do not react with solutions that imitate the liquid environments of the human body.

3D finite element analysis and experimental correlations of laser synthesized AlCrNiTiNb high entropy alloy coating

A 3D Finite Element Analysis (FEA) model of laser cladding process of AlCrNiTiNb high entropy alloy (HEA) coatings on Titanium alloy (Ti6Al4V) substrate has been developed taking into account heat transfer and free surface movement. The use of Ti6Al4V is highly evident in applications such as aerospace, automobile and marine environments due to their outstanding specific strength to weight ratio. Although they have high strength useful for fabrication of engineering components and movable parts in a mechanical system, Ti6Al4V are restricted to non-friction applications as a result of their low hardness. In this work, AlCrNiTiNb HEA hard-coating with equi-atomic ratio was synthesized on Ti6Al4V alloy substrate by laser cladding technique to mitigate the limitations. Prior to experimental method, a 3D computational model was developed to simulate the physical phenomena based on heat transfers involved during laser surface cladding (LSC) of HEA coating on Ti‐6Al‐4V alloy by a laser-assisted direct energy deposition technique. COMSOL Multiphysics 5.3a was used to create a model using heat transfer in solids module incorporating temperature distribution during the layer-wise build-up of 3 layers. The experimental validation showed that the microstructural analysis by scanning electron microscope (SEM) resulted in coating having dendritic and interdendritic structure which resulted in good metallurgical bonding. X-ray diffraction (XRD) analysis displayed that AlCrNiTiNb alloy coating is composed of ordered and disordered solid solution phases (BCC and FCC) with no intermetallic compounds formed. Energy dispersive spectrometer (EDS) confirmed the presence of elements used. The microhardness of AlCrNiTiNb HEA coating reached maximum value around 892 HV which is more than of the substrate. The microhardness increased significantly due to the combination of BCC and FCC solid solution phases.

Enhanced Anticoagulation of Hierarchy Liquid Infused Surfaces in Blood Flow.

Liquid infused surfaces (LIS) hold remarkable potential in anticoagulation. However, liquid loss of LIS in the bloodstream remains a challenge toward its clinical application. Here, micronano hierarchy structures are obtained on the titanium alloy substrate by regulating the microspheres' distribution. When the gap between the microspheres is smaller than the diameter of the red blood cell (RBC), the LIS is more stable under the blood wash and presents a better anticoagulation performance. The proper interval is found to prevent the RBCs from entering the gap and remove the liquid on the surface. The retained thickness of the liquid film is measured by the atomic force microscopy (AFM) technique. The LIS is applied on the front guide vane of an artificial heart pump and exhibits significant improvement on anticoagulation in the blood circulation in vitro for 25 h. The techniques and findings can be used to optimize the anticoagulation performance of LIS-related biomedical implant devices.

Influence of niobium and hafnium doping on the wear and corrosion resistance of coatings based on ZrN

The properties of coatings based on the ZrN system with the introduction of hafnium and zirconium (ZrN, (Zr,Nb)N and (Zr,Hf)N), deposited on a Ti6Al–4V titanium alloy substrate are compared. Coatings are deposited by controlled accelerated arc-physical vapor deposition, and the structure of the coatings is studied using a transmission electron microscope. A comparison is made of both the mechanical (hardness, wear resistance, scratch strength) and anticorrosion (in a 3 % solution of NaCl) properties. The (Zr,Hf)N coating (22 at% Hf and 78 at% Zr) has the maximum hardness (HV, 3225 ± 73) and wear resistance. This coating also exhibits higher corrosion resistance. In contrast, introducing Nb into the coating composition reduces the corrosion resistance. This combination of beneficial properties makes the (Zr,Hf)N coating useful for conditions in which the surfaces of parts must simultaneously have high wear resistance, strength, and corrosion resistance.

Ablation resistance of SiC-modified nanocomposite ceramic coating prepared by LPDS method on titanium alloy

To enhance the ablation resistance of Ti6Al4V alloy, a SiC-modified nanocomposite ceramic coating was fabricated by a novel one-step liquid plasma-assisted particle deposition sintering (LPDS) method. A microarc oxidation (MAO) ceramic coating was prepared on the surface of titanium alloy as a comparison. The micromorphologies and formation mechanisms of two ceramic coatings were investigated with the assistance of scanning electron microscopy (SEM), X-ray diffractometer (XRD), and transmission electron microscopy (TEM). The thickness of the SiC nanocomposite coating (about 39 μm) was significantly increased by 129% compared to the MAO coating (about 17 μm). Additionally, ablation tests of Ti6Al4V alloy, MAO coating, and SiC nanocomposite coating were conducted at 1000 °C using a butane gas lance. Then, the variation of microstructure, phases, elemental composition, and thickness before and after ablation was also comparatively analyzed. The results indicate that the SiC nanocomposite coating exhibits the smallest thickening (29 μm) after ablation at 1000 °C for 360 s, which is 39% and 46% compared with the Ti6Al4V substrate and MAO coating, respectively. The nanocomposite coating is intact and cracks-free after the ablation test. SiO2, formed during the ablation of SiC nanocomposite coatings, blocks oxygen diffusion into the substrate, which plays a protective role in the coating. Therefore, the SiC nanocomposite coating by a novel LPDS technique exhibits superior ablation resistance to enhance the thermal protection performance of titanium alloy substrate.

Antibacterial and corrosion resistant ANPs-TaC nanocomposite coating for biomedical applications

To improve the antibacterial properties of metallic implants to hinder the colonization of bacteria on their surfaces, an Ag nanoparticle (ANPs)/TaC nanocomposite coating was synthesized on a titanium alloy substrate by a double cathode glow discharge approach. The nanocomposite coating was composed of AgNPs (~13 nm in diameter) embedded in a nanoscale TaC matrix, with a mean grain size of 8 nm. The nanocomposite coating exhibited a bilayer structure, composed of a compact inner layer and a cauliflower-like outer layer. The corrosion resistance of the nanocomposite coating in both a 0.9 wt% NaCl solution and Ringer's solution was studied in comparison with both uncoated Ti-6Al-4V (TC4) and an Ag-free TaC coating by using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). These results showed that the incorporation of Ag nanoparticles slightly lowered the corrosion resistance of the TaC coating. The antibacterial activity of the ANPs-TaC nanocomposite coatings against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Salmonella Typhimurium (Salmonella) strains was examined based on the bacterial inhibitory zones and bacterial killing efficiency. The addition of ANPs markedly increased the antibacterial capacity of the TaC coating against all three types of microorganisms. Therefore, a unique combination of the electrochemically stable TaC phase, together with the antibacterial behavior of the ANPs, makes the ANPs-TaC nanocomposite coating an attractive choice in the design of next-generation biomedical implants.

The Surface Modification of ZrO2 Film by Zr/Nb Ion Implantation and First-Principles Calculation

Zirconium dioxide (ZrO2) possesses numerous advantages such as high mechanical strength, a low friction coefficient, excellent optical properties, and an extended lifespan. Consequently, ZrO2 has a broad research foundation and practical significance in functional films and wear-resistant coatings. However, it suffers from brittleness and low ductility when used as a bio-coating material. In this study, a ZrO2 film was fabricated on Si (100) and titanium alloy substrates using a magnetron sputtering system. Subsequently, Zr and Nb ions were implanted into the film at varying doses, but with consistent energy levels. The analysis focused on the film’s microstructure, mechanical properties, hydrophilicity, and corrosion resistance. The results demonstrate a significant improvement in the hydrophilicity and corrosion resistance of the ZrO2 film following the implantation of Zr and Nb ions. First-principles calculations based on density functional theory (DFT) principles indicated that, with increasing doping concentrations of Zr and Nb in the ZrO2 model, the stability of the model increased gradually, thereby enhancing its corrosion resistance. The developed product has propelled rapid advancements in fields such as biomedical implants.

Influence of atomic size effect on the properties of high entropy alloy coatings

In this study, laser cladding was used to prepare four high-entropy alloy coatings (HEACs) with different hardness on the titanium alloy substrate. Their hardness is based on the lattice distortion parameter (dimensionless parameter ε) for selection. Nominal composition of the four coatings designed basing on gradient lattice distortion parameters is CoCr0.5Fe2NiTi0.25 (ε = 4.64), CrMnMoTiV (ε = 6.10), CrFeMnMoTi (ε = 7.32), and CrMoNbTiZr (ε = 10.72). The phase composition of alloy coating systems is mainly fcc or bcc disordered solid solution accompanied by intermetallic compounds. The hardness of four coatings highly accord with the rule of “Hardness∝ε”, and theirs show the abrasive wear mechanism. As hardness of the coating increases, the coefficient of friction and wear loss decrease. Moreover, erosion resistance performance also shows similar results as friction test. In general, the method designing the hardness of high entropy alloy coatings is proven to be feasible herein. It provides favorable guidance for the development of the HEACs system with required hardness.

The Interplay of Thermal Gradient and Laser Process Parameters on the Mechanical Properties, Geometrical and Microstructural Characteristics of Laser-Cladded Titanium (Ti6Al4V) Alloy Composite Coatings

With the development of laser surface modification techniques like direct laser metal deposition (DLMD), titanium alloy (TI6Al4V) may now have its entire base metal microstructure preserved while having its surface modified to have better characteristics. Numerous surface issues in the aerospace industry can be resolved using this method without changing the titanium alloy’s primary microstructure. As a result, titanium alloy is now more widely used in sectors outside of aerospace and automotive. This is made possible by fabricating metal composite coatings on titanium alloys using the same DLMD method. Any component can be repaired using this method, thereby extending the component’s life. The experimental process was carried out utilizing a 3000 W Ytterbium Laser System at the National Laser Centre of the CSIR in South Africa. Through the use of a laser system, AlCuTi/Ti6Al4V was created. The characterization of the materials for grinding and polishing was performed according to standard methods. There is a substantial correlation between the reinforcement feed rate, scan speed, and laser power components. Due to the significant role that aluminum reinforcement played and the presence of aluminum in the base metal structure, Ti-Al structures were also created. The reaction and solidification of the copper and aluminum reinforcements in the melt pool produced the dendritic phases visible in the microstructures. Compared to the base alloy, the microhardness’s highest value of 1117.2 HV1.0 is equivalent to a 69.1% enhancement in the hardness of the composite coatings. The enhanced hardness property is linked to the dendritic phases formed in the microstructures as a result of optimized process parameters. Tensile strengths of laser-clad ternary coatings also improved by 23%, 46.2%, 13.1%, 70%, 34.3%, and 51.7% when compared to titanium alloy substrates. The yield strengths of laser-clad ternary coatings improved by 19%, 46.7%, 12.9%, 69.3%, 34.7%, and 52.1% when compared to the titanium alloy substrate.

Microstructure performance and Nano-Effect of laser alloying composites with Multi-Phase on TA1 titanium alloy

Laser alloying (LA) of the Nimonic93-Zn-SiB2-CeO2 mixed powders formed a first layer by the coaxialpowderfeedingon a TA1 titanium alloy substrate; then the mixture powders of FeCoCrAlCu-TiC was alloyed on this formed first layer also by the coaxialpowderfeeding to produce the high entropy alloys (HEAs) base layer, forming the composites. The nanocrystals and the graphene oxide sheets (Graphene oxide sheets, GOSs)/CNTs reinforced layer were formed on an second layer, also by mean of LA of FeCoCrAlCu-TiC-(GOSs/CNTs). Portions of the produced ultrafine particles (UPs) were able to disrupt the balanced state of the atoms, enhancing the free energy of the crystal boundaries of such composites; UPs should diffuse into every locations of a laser-pool (LP) with an extreme high temperature as soon as possible. Wear performance of such composites was significantly higher than that of TA1 under an action of multi-phase. Identification of synthetic UPs in such fabricated composites, more importantly an UPs effect, contributes theoretical/experimental basis to upgrade quality of the laser fabricated materials with multi-phase.

Characterising Hydroxyapatite Deposited from Solution onto Novel Substrates: Growth Mechanism and Physical Properties.

Whilst titanium, stainless steel, and cobalt-chrome alloys are the most common materials for use in orthopaedic implant devices, there are significant advantages in moving to alternative non-metallic substrates. Substrates such as polymers may have advantageous mechanical biological properties whilst other substrates may bring unique capability. A key challenge in the use of non-metal products is producing substrates which can be modified to allow the formation of well-adhered hydroxyapatite films which promote osteointegration and have other beneficial properties. In this work, we aim to develop methodology for the growth of hydroxyapatite films on surfaces other than bulk metallic parts using a wet chemical coating process, and we provide a detailed characterisation of the coatings. In this study, hydroxyapatite is grown from saturated solutions onto thin titanium films and silicon substrates and compared to results from titanium alloy substrates. The coating process efficacy is shown to be dependent on substrate roughness, hydrophilicity, and activation. The mechanism of the hydroxyapatite growth is investigated in terms of initial attachment and morphological development using SEM and XPS analysis. XPS analysis reveals the exact chemical state of the hydroxyapatite compositional elements of Ca, P, and O. The characterisation of grown hydroxyapatite layers by XRD reveals that the hydroxyapatite forms from amorphous phases, displaying preferential crystal growth along the [002] direction, with TEM imagery confirming polycrystalline pockets amid an amorphous matrix. SEM-EDX and FTIR confirmed the presence of hydroxyapatite phases through elemental atomic weight percentages and bond assignment. All data are collated and reviewed for the different substrates. The results demonstrate that once hydroxyapatite seeds, it crystallises in the same manner as bulk titanium whether that be on a titanium or silicon substrate. These data suggest that a range of substrates may be coated using this facile hydroxyapatite deposition technique, just broadening the choice of substrate for a particular function.

Дослідження впливу температури газу процесу холодного газодинамічного напилювання на адгезійну міцність нікелевмісних покриттів

The subject of the research is the influence of low-pressure cold spraying process parameters on the adhesive strength of the coatings. The goal is to ensure the maximum values of the adhesive strength of nickel-based coatings deposited by cold spraying by controlling the gas temperature at the nozzle inlet. The task is to investigate the effect of the temperature mode of the DYMET-405 machine on the adhesive strength of the coatings obtained from the Ni+Zn+Al2O3 powder mixture at constant other spraying parameters. Research methods. The experimental study of the adhesive strength was conducted on the tear using adhesive method in accordance with DSTU 2639-94. The metal-matrix composite powder mixture Ni+Zn+Al2O3 was used as powder material. VT3-1 titanium alloy was chosen as substrate material. Coatings were deposited using DYMET-405 low-pressure cold spraying machine. Temperature regulation at the nozzle inlet was performed by turning on the required temperature mode on the equipment control panel. Other spraying parameters remained constant during coating deposition process. The results. It was established that with an increase in the temperature of the gas in the nozzle, an increase in the adhesive strength of coatings is observed, on average from 9.5 MPa to 28.7 MPa. This can be explained by the fact that an increase in gas temperature leads to an increase in the velocity of the gas flow and, accordingly, of the powder particles in this flow. Higher particle impact velocity has a positive effect on the process of their deforming, filling of pores, densifying of coating layers, and finally increasing the adhesive and cohesive strength. The scientific novelty of the obtained results is that the dependence of the gas temperature at the nozzle inlet during low-pressure cold spraying on the adhesive strength of Ni+Zn+Al2O3 powder mixture coatings deposited on VT3-1 titanium alloy substrates was obtained. Conclusions. The practical value of the obtained results is that the obtained dependences of adhesive strength on gas temperature can be used for the development of cold spraying recommendations for the deposition of restorative coatings on parts made of titanium alloys, in particular in aircraft engines to eliminate operational defects.

Synthesis of TiO2/rGO composite coatings on titanium alloys with enhanced anticorrosion performance in palmitic acid-incorporated physiological solutions

During plasma electrolytic oxidation (PEO) process, molten oxide is rapidly solidified through arc discharges in order to create in-situ ceramic TiO2 coatings on titanium alloy substrates. PEO coatings made on biomedical titanium alloys may have limited protection efficiency in organic acid-containing biological solutions due to their inherent porosity. In order to elevate the anticorrosion performance of these coatings, a second layer can be applied to the top surface of the PEO coatings to seal the cracks and pores by other surface engineering methods. In current work, the reduced graphene oxide (rGO) nanosheets were electrophoretically deposited on the Ti–6Al–4V substrate involving an intermediate TiO2 oxide layer applied PEO process. Electrochemical measurements in palmitic acid-containing biological media showed that the duplex TiO2/rGO coating has higher compactness and better corrosion performance than simple TiO2 coating. Indeed, the synthesis of the TiO2/rGO coating on the Ti alloy results in a decrease in the corrosion current density (2.19 μA‧cm−2) in comparison with the simple TiO2 coating (9.85 μA‧cm−2) in an acidic media.