Multilayered and nanostructured coatings of Ti based alloys (oxides and nitrides) are elaborated and tested for increasing protective properties such as corrosion and wear resistances. A pin-on-disc tribometer was used to evaluate the wear resistance in Hank's solution against bovine bone. Corrosion behavior in Hank's solution was determined by potentiodynamic and electrochemical impedance spectroscopy techniques. Besides, the specimen surfaces were characterized by Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) microanalyses. The results showed that optimal tribological properties were obtained in the case of coatings having TiN as top layer. The main wear mechanism was abrasive third body wear. In vitro corrosion tests at 37 °C showed that the better corrosion resistance was obtained when TiN was the top layer. However all of them exhibited good tribological properties, good corrosion resistance and then may be promising options for biomedical applications.

High-throughput roll-to-roll processing could be used to scale up the manufacture of flexible thermoelectric generators. Very thin thermoelectric layers can be manufactured at high throughput speed and low cost and, most importantly, are predicted to possess better thermoelectric properties than thicker layers. Here we present a study on a series of bismuth telluride films of different thickness (few nm to 370 nm), deposited on polymer substrates at room temperature using DC magnetron sputtering. Unlike previous studies of deposition of bismuth telluride films onto heated substrates, an island-growth mode, indicated by AFM, was observed for Bi-Te films grown at room temperature. A period of growth in which the layer only partially coats the substrate, with only imperfect connections between islands, was observed. In this partially coated region, the coating exhibited an extremely high Seebeck coefficient. An energy barrier mechanism, similar to the interface effect in nanomaterials, is proposed to explain this phenomenon, along with a possible quantum confinement effect. We found that a thinner Bi-Te film could generate a greater power factor because of a quasi-decoupling of Seebeck coefficient and electrical resistivity. In addition, ensuring that the sample passed directly under the sputtering target, and using a substrate smoothed with an acrylate layer were found to improve film properties, thus enhancing thermoelectric behaviour.

Cu species (Cu/Cu2O/CuO NPs) functionalized fabric (Cu-fabric) with superhydrophobicity was fabricated through a simple in-situ reduction from Cu(OH)2-coated-fabric and an immersion process in n-octadecathiol (ODT) solution, in which cotton fabric served as bio-support material to immobilize Cu2+ in the presence of NH3·H2O. The surface morphology, elements composition, elements valance state and functional groups were detected by SEM, EDS, XPS and ATR-FTIR, respectively, and a formation mechanism of the Cu-fabric was proposed. The as-prepared Cu-fabric showed superhydrophobicity to deionized water, with a water contact angle (WCA) about 153.5° and a sliding angle (SA) about 10°, and good hydrophobicity to the other common household liquids. In addition, the Cu-fabric maintained chemical stability after 72 h under different extreme conditions, and mechanical durability after 200 cm of abrasion length. Furthermore, the separation efficiency of light oil/water mixtures with Cu-fabric was above 97% for n-dodecane, n-hexane, kerosene, cyclohexane and n-heptane and Cu-fabric maintains a high separation efficiency for n-dodecane and n-hexane after 30 separation cycles. The as-prepared Cu-fabric exhibited potential for practical application in oil/water separation of oil-contaminated industrial sewage in complicated environments.

The paper presents the results of the investigation into the formation of the nanolayer structure of the Ti-TiN-(Ti,Cr,Al)N coating and its influence on the thickness of coatings, their resistance to fracture in scratch testing, and the wear resistance of coated tools in turning 1045 steel. The structure of the coatings with the nanolayer thicknesses of 302, 160, 70, 53, 38, 24, 16, and 10 nm was studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution (HR) TEM. It is shown that the grain sizes in the nanolayers decrease to certain values with an increase in the thickness of the nanolayers, and then, with a further decrease in the nanolayer thickness, the grain sizes of the nanolayer grow as the interlayer interfaces cease to produce a restraining effect on the growth of the grains. The study found that the nanolayer thickness influenced the wear of carbide cutting tools and the pattern of fracture for the Ti-TiN-(Ti,Cr,Al)N coatings.

The effects of cold SF6 plasma treatment on amorphous hydrogenated carbon (FA), polypropylene (PP) and polystyrene (PS) were investigated as functions of gas pressure and applied power. An anticipated increase in hydrophobicity was confirmed by the greater water contact angles, θ, observed after all the treatments. Under the best conditions θ was increased by 50.8°, 57.2° and 21°, respectively. A rise and fall in θ was observed as the pressure of SF6 was increased, this trend being most consistent for FA. Although the plasma treatments caused some changes in surface roughness, measured using profilometry, there were no clear correlations between this parameter and θ. As revealed by Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Photoelectron Spectroscopy (XPS), the treated surfaces were fluorinated. As the degree of fluorination under optimal conditions was 2.2 at.%, 10.4 at.% and 36.3 at.% for the FA, PP and PS, respectively, this factor was not alone responsible for the observed increases in θ. Sulfur was attached to the surface of all the treated samples. The relative surface carbon content was reduced by the treatments. The main causes of the changes in θ upon treatment were the induced compositional and structural changes. Ageing for ten days caused a typical decrease in θ of ~10°, probably caused by rotation of hydrophobic surface groups into the surface.

The effects of ultrasonic impact peening (UIP) and laser shock peening (LSP) on 316L stainless steel were compared in terms of surface morphologies, microstructural evolutions and mechanical properties. The grain refinement mechanisms by mechanical and laser shock wave were subsequently analyzed. Experimental results showed that both UIP and LSP produced micro-grooves with the same depth (~48 μm) at the surface of 316L. The nano-grain size induced by double UIP treatment (10–90 nm) was much smaller than that by triple LSP treatment (>70 nm) because the impact numbers and total impact energy of UIP were much higher. The mechanical twinning was almost complete absence in the sample by UIP. On the contrary, the mechanical twinning was frequently observed in samples by LSP. The magnitude of peak pressure determined the transition from dislocation-dominated mechanism (~680 MPa for UIP) to twinning-dominated mechanism (~2200 MPa for LSP). The resultant dislocation cell size by UIP was much smaller than that by LSP due to the difference of dislocation density caused by different shock wave speed and impact numbers. Additionally, the compressive residual stress on the surface by UIP was higher than that by LSP in both measuring direction. Furthermore, both grain refinement and high dislocation density induced by UIP contributed to a significant increase in the hardness (~433 HV) and yield strength (~447 MPa). By contrast, the LSP induced mechanical twins which can act as dislocation blockers significantly improved the yield strength (~423 MPa).

In this study, NiAl coating was produced on 304 stainless steel material using High velocity oxygen-fuel (HVOF) spray technique. The influence of oxygen flowrate on the microstructure, porosity and hardness of the coating was investigated. Further, the mechanical properties of HVOF sprayed samples were determined at various temperatures using optical, laser excitation with interferometer reception, completely non-contact and nondestructive based laser ultrasound technique. The outcomes of this study indicate that the microstructure and properties of the coatings are sensitive to the oxygen flowrate. A coating with highest hardness and less porosity was achieved while increasing the oxygen content. Higher Young's modulus was observed at 20 °C and gradually decreases with the rise in temperature. The behavior of Young's modulus and Poisson's ratio at elevated temperature indicates that originate from the existence of a gas flow rate in the NiAl coating, leading to reduced flexural strength with increased temperature. Both inversion and experimentation result shows a good agreement in elastic properties of HVOF coated sample. The proposed laser ultrasound technique is valid for remote, noncontact and nondestructive characterization of the Young's modulus and Poisson's ratio of the coatings in elevated temperature environments.

In this paper, titanium nitrides were produced on commercially pure titanium samples by laser nitriding processes, with the goal of improving bio-compatibility and corrosion resistance. To identify the critical set of laser nitriding processing parameters (a combination of both laser scanning parameters and the N2 content processing gas), mouse MLO-Y4 cells were utilized for bio-compatibility evaluation, and simulated body fluid was used for electrochemical behavior examination to characterize corrosion performance. The modified surfaces were also characterized with scanning electron microscope, X-ray diffraction, and nano-indentation techniques to reveal the connections between the bio-compatibility/corrosion resistance performance and the nitrided layer composition, thickness, and surface roughness. For improved bio-compatibility and corrosion resistance performance, a dense and thick titanium-nitride dendritic layer is desirable, which can be formed in a pure N2 environment, together with a high laser energy density.

In this study, amorphous carbon buffer layer containing nano-crystalline diamond grains was pre-deposited on single crystal silicon (Si) wafers. (100) oriented diamond films were prepared on the buffer layer by increasing deposition temperature. Morphology observation demonstrated that (100) oriented diamond plates appear on the buffer layer, thus realizing the deposition of (100) oriented diamond film. Transmission electron microscopy confirmed that (100) oriented diamond dominates deposition at high temperatures, leading to the formation of the (100) oriented diamond plates. The fast lateral growth of nano-crystalline diamond grains with (100) orientation in the buffer layer is the main driving force for the deposition of (100) oriented diamond film, providing a new route for the preparation of (100) oriented diamond films.

Based on the high-power and high-flow mode of the three-cathode high-energy plasma spray system, Mo coatings were prepared on the surface of 15-5PH steel, and the effects of different auxiliary gas (helium) flow parameters on the micro-morphology and properties of the coating were studied. X-ray diffraction (XRD), scanning electron microscope (SEM), micro-hardness tester, universal testing machine, and friction and wear testing machine were used to characterize the phase composition, micro-morphology, micro-hardness, combining strength and tribological properties of the coating. The results showed that the surface of the Mo coating prepared by high-energy plasma spraying had visible pit shapes. The coating porosity gradually decreased along with the thickness of the coating, showing a typical tamping morphology. Due to the breakneck flying speed and deposition speed of powder particles, no apparent oxidation phenomenon was observed in the coating. With the increase of auxiliary gas flow, the tamping effect of the powder particles on the coating increased, and the density, hardness, and bonding strength of the coating increased. With the increase of auxiliary gas flow, the wear rate of the coating decreased, and the wear mechanism of the coating gradually changed from abrasive wear to adhesive wear.

A convenient coating process was developed to prepare zirconia-coated zirconium diboride (ZrB2@ZrO2) powder by in-situ passivation reaction in the mixed hydrothermal solutions of sodium hydroxide (NaOH) and hydrogen peroxide (H2O2). Amounts of techniques consisted of field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) were used to study the effects of coating parameters (NaOH concentration, H2O2 concentration, reaction temperature and reaction time) on the microstructure and composition. The results show that the coated powder exhibits a flat surface similar to the raw powder. The coating has a full coverage and its content is controllable by adjusting reaction time. It has a double layered structure. The inner layer of the coating mainly derived from the in-situ passivation reaction is the mixture of tetragonal zirconia (t-ZrO2) and amorphous zirconia (a-ZrO2). The outer layer produced by the hydrothermal crystallization process is monoclinic zirconia (m-ZrO2). The coated powder with 30 wt% ZrO2 has excellent sintering property and contributes to reforming a dense coated structure of the sintered composite. Thus, its oxidation resistance is significantly improved at 1400 °C.

Nowadays, the practical application of the super-hydrophobic surfaces is limited by their mechanical durability. In this work, robust super-hydrophobic cobalt-nickel coatings reinforced by micro-nano tungsten carbide (WC) particles were achieved on carbon steel substrate by electrochemical deposition from the mixed solution. The effect of WC particles content on the surface morphology, wetting properties and the corrosion protection performance of the composite coatings were investigated. The linear abrasion test indicated that the as-prepared super-hydrophobic CoNi/WC composite coating with 9.8 wt% WC content, displayed excellent wear resistance with super-hydrophobic property for abrasion distance up to 34 m. Furthermore, the super-hydrophobic CoNi/WC coating with robust mechanical durability can be a promising alternative technique for corrosion protection.

The roles of surface roughness on icephobicity including ice adhesion strength have been long debated in icephobicity studies. However, the direct/systematic influence of surface roughness on ice adhesion strength while keeping other surface characteristics such as surface wettability and interfacial cavitation unchanged are seldom reported. In this paper, systematic reduction of ice adhesion strength with the decrease in surface roughness regardless of the surface wettability was demonstrated across all the studied material types, i.e. metallic surfaces and polymeric coatings with different surface wettability. In-situ icing observation studies indicated that the ice did not anchor on smooth metallic surfaces and polymeric coatings but anchored on rough surfaces including superhydrophobic coatings. Effect of surface wettability was argued against the ice adhesion strength based on our results and similar ice adhesion strength was found on materials having different wettability (i.e. hydrophilic and hydrophobic coatings, and surfaces having different contact angle hysteresis). On the contrary, the introduction of low surface energy chemicals (via deposition and/or functionalization) on the surface having similar surface roughness showed a direct reduction of ice adhesion strength. These results indicated the surface roughness is vital in achieving icephobic performance, however, the ultra-low ice adhesion strength could be achieved by the synergetic effect of low surface roughness and low interfacial cavitation (in line with the interfacial correlation factor).

In this study, Inconel 718 coatings were fabricated by high pressure cold spray deposition and the microstructure and tribological properties of the coatings were systematically investigated at both room and elevated temperatures. At the first place, the investigation on the effect of thermal exposure on the surface oxidation of the coatings was conducted in the absence of sliding. It was found that oxides started to form on the coating surface when the ambient temperature was above 500 °C. At 600 °C, a NiFe2O4 spinel oxide layer spread over the coating surface. Under sliding against an Al2O3 counter ball, oxides started to form on the coating surfaces in contact with the ball when the ambient temperature was above 200 °C due to the fact that the frictional and external heat had facilitated the formation of the oxides. Thus, the friction coefficients of the Inconel 718 coatings decreased with the increase of ambient temperatures. However, the wear rates of the coatings increased at 100 °C and 200 °C compared to those of the coatings tested at room temperature, which was due to the decrease of hardness and severe abrasive wear. When the ambient temperature was further increased to 300 °C, a transition in wear mechanism occurred and the wear rates decreased due to the formation and breakage of the surface oxides that could act as lubricants between the counter ball and coating. With further increase of ambient temperature, a ‘glaze’ layer was formed and grew on the wear tracks, which could act as a protective layer and showed a load-bearing effect that prevented further removal of the coating materials, resulting in an improved wear resistance of the Inconel 718 coatings at elevated temperatures. Therefore, cold sprayed Inconel 718 coatings could be potentially used under wear conditions at elevated temperatures.

A new method for preparing composite materials on metal surfaces by injecting high-speed solid particles is proposed. High-speed 316L stainless steel particles accelerated using high-pressure nitrogen in a de Laval nozzle were injected into an aluminum surface to form an Al/316L composite surface without the buildup of a coating. The acceleration and injection processes of the 316L particles were simulated. The injection and deposition behaviors of the 316L stainless steel particles on the aluminum substrate were investigated. The compressive stress strengthening induced by the tamping effect was also studied. It was shown that the strengthening of the Al/316L composite surface achieved via both shot peening and the metal matrix composites, known as the double-strengthening effect, significantly improved the wear resistance of the aluminum substrate. In addition, the introduction of beneficial compressive residual stress on the surface of the material was shown to effectively improve the anti-adhesive wear and fatigue wear resistance.

The phase formation behavior of carbon-doped TiZrN upon the variation of thermal energy was investigated in terms of microstructure and bonding state. The laser output was changed by 10% in the range of 20% to 70% after covering the carbon paste on the TiZrN coating. Degradation occurred on the coating surface by the laser ablation of 60% and 70% output. Phase analysis and the Rietveld refinement for the coating, which did not exhibit degradation, indicated that the phase fraction of the graphite inside the coating increased as the thermal energy increased. The lattice constant of TiZrN was 0.431 nm initially, but it gradually increased to 0.449 nm at the output of 50%. FIB, Cs-TEM, and TEM-EDS analyzed the formation of (Ti, Zr)C phase and the variation of lattice constant via cross-sectional microstructure and showed the increase in carbon content and carbon-substituted (Ti, Zr)C phase formed along with the existing (Ti, Zr)N phase. XPS analysis for the bonding of the doped carbon indicated that the substitution ratio of the doped carbon was approximately 4.4% at the output of 20%, and the substitution rate increased with increasing thermal energy resulting in 19.6% at the output of 50%. The ZrC phase mostly existed at the output of 20% for the substitutional carbon, and the proportion of the TiC phase increased with the increase in thermal energy, resulting in more than 50%. The formation energy of ZrC phase was lower than that of TiC phase, and the formation energy of TiC was satisfied with the increase in thermal energy. The hardness increased to 38.3 GPa at the output of 50% as the ratio of TiC phase was increased, which was approximately 20% higher than that of the TiZrN.

This investigation concerns the mechanisms by which (fine) particles become incorporated into plasma electrolytic oxidation (PEO) coatings when added to the electrolyte. Three different types of particle have been used, covering a wide size range, and processing has been carried out with both Al and Ti substrates. For some of these combinations, the particulate was chemically similar to the expected PEO product, while for others it was different. The power supply was 50 Hz AC, with a pre-selected current density. It has been established that, where such reactions are chemically favoured, phase changes can occur that must have involved the particulate reaching very high temperatures. From this and other evidence, it is concluded that the main incorporation mechanism involved is that of (fine) particulate being swept into the pores associated with active discharge sites, while they are being refilled with electrolyte immediately after collapse of the plasma. They are then likely to become entrapped, and in many cases to be strongly heated as the plasma is created during the next discharge cycle. Typical pore sizes are such that particles (or particulate clusters) above about 10 μm in size would be unlikely to enter them. While particles a few microns in diameter can become incorporated, it takes place more readily with sub-micron particles. It is also concluded that electrophoretic forces are unlikely to play any significant role in the incorporation process.

The tungsten-copper composites are used in industry as electrical contact materials due to high thermal conductivity, high melting temperature of tungsten and low coefficient of thermal expansion. In this work the process of deposition of the composite copper-tungsten cold spray coating was studied. Kinetics of the coating formation process was analyzed using specially developed analytical model based on the probability approach. It was shown the mass percentage of tungsten mass percentage in the coating could not exceed 52%. The modeling results were in good agreement with experimental data. Thermal conductivity of the composite coatings with different tungsten percentage was experimentally measured and compared with the theoretical results calculated using Hasselman – Johnson model. It was found that the thermal conductivity of the copper-tungsten coating depended on the percentage of the tungsten.

Within this work, MoNbTaVW high entropy alloy thin films were synthesized by dc magnetron sputter deposition, high power impulse magnetron sputtering and cathodic arc deposition to study the influence of the growth conditions on structure and properties of the films. For deposition angles ranging from 0 to 90°, the deposition rate, chemical composition, morphology and crystal structure as well as the mechanical properties were analyzed. All films showed the formation of a solid solution with body centered cubic structure regardless of deposition angle and method, whereas higher energetic growth conditions were beneficial for improved mechanical properties.

During Precision Glass Molding (PGM), the molding tools have to withstand severe thermo-chemical and thermo-mechanical loads cyclically. To protect their high-quality optical surface against degradation and increase their service lifetime, protective coatings are applied on the molding tools. In this work, we designed four different PtIr protective coating systems, where the thickness of the PtIr layer and the adhesion layer were varied. Their lifetimes were evaluated and compared using an in-house built testing bench. Among all the studied coating systems, the protective coating, which consists of a 600-nm-thick PtIr layer and a 20-nm-thick Cr adhesion layer, showed the best durability with the longest lifetime. To understand the degradation mechanism of the coating during actual engineering production, an industrial PGM machine was used and emulation PGM tests were conducted. Detailed sample characterization was performed using an array of complementary techniques including white light interferometry (WLI), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), scanning transmission electron microscopy (STEM) and atom probe tomography (APT). Phenomena such as interdiffusion, oxidation, coating spallation and glass sticking on the coating were observed and are discussed in the context of optimization of the coating's performance and durability.

Nanoplasmonic thin films, composed of Au nanoparticles dispersed in a ZnO matrix were produced and characterized for Localized Surface Plasmon Resonance (LSPR) applications. The thin films were deposited by reactive magnetron sputtering, with different gold pellets area placed within the erosion zone of the target, followed by post-deposition thermal annealing to promote the nanoparticles' morphological evolution, necessary to obtain the desired LSPR bands. Four sets of thin films were prepared, containing Au atomic concentrations of 0, 9.3, 12.4 and 18.4 at.%. The Au nanoparticles were formed in a nearly stoichiometric and polycrystalline ZnO matrix, and observed in different stages of their growth, in size and shape, depending on the thermal annealing. As both annealing temperature and gold concentration were raised, large and irregular nanoparticles were formed, due to coalescence processes. For the highest concentration, there was a clear Au segregation, with the formation Au crystals (average sizes in the order of 1 μm) at the thin film's surface. Well-defined LSPR bands appeared in the films with Au concentrations of 9.3 and 12.4 at.%, but only at higher annealing temperatures (400 and 600 °C), with resonance peaks in the range from 570 nm to 615 nm. The increase of the annealing temperature also improved the LSPR properties of the Au-ZnO thin films, namely a two-fold increment of the refractive index sensitivity, showing promising responses to be tested in plasmonic applications.

Based on the thermal elastic-plastic finite element theory and ANSYS finite element analysis software, a numerical model of Mo/8YSZ functionally gradient thermal barrier coatings prepared by the plasma spraying technology on the surface of aluminum alloy was established. The model considered the change of the thermophysical properties of the material with temperature and analyzed the influence of different preheating temperatures of the substrate on the value and distribution of the residual stress of the functionally gradient thermal barrier coating. The results showed that as the preheating temperature of the substrate increases, the distribution range of the radial residual tensile stress of the coating gradually decreased, and the distribution range of the radial residual compressive stress gradually increased. However, as the preheating temperature of the substrate increases, the distribution range of the axial residual tensile stress of the coating gradually increased and the distribution range of the axial residual compressive stress gradually decreased. With the increase of the preheating temperature of the substrate, the maximum value of the radial residual tensile stress, the maximum value of the radial residual compressive stress and the maximum value of the axial residual compressive stress of the component increased, but the maximum value of the axial residual tensile stress of the component showed a tendency of decreasing first and then increasing. Compared with the axial residual tensile stress of the component, the change of the preheating temperature of the substrate had a greater impact on the axial residual compressive stress, the radial residual compressive stress and the radial residual tensile stress of the component. Compared with other locations of the interface between the substrate and the coating, there was a larger abrupt change in the residual stress at a position about 0.5 mm from the edge of the interface. Considering the distribution of residual stress and sudden changes in stress, the preheating temperature of the substrate should be controlled at 150 °C.

Mechanical properties of thin films and, in particular, adhesion are crucial engineering parameters which must be determined to allow their successful application both in the industry and science. Deposited hydrogenated amorphous carbon-silicon (a-CSi:H) films prepared by plasma-enhanced chemical vapour deposition (PECVD) were tested using a nanoscratch test. The load at which adhesion failure occurs is known as the critical normal load and is used as a semi-quantitative measure of adhesion. However, results in this article suggest that the critical normal load is not an appropriate measure of adhesion for these materials, and instead, the work of adhesion should rather be considered as an alternative method. This is due to the considerable variation of Young's modulus, which affects the critical load figures, while the friction coefficient and film thickness also do not have negligible influence. Moreover, the critical load is considerably influenced by intrinsic and extrinsic parameters. Furthermore, it has been found that the critical load increased with increasing a-CSi:H film thickness, but this did not apply to the work of adhesion. On the contrary, it remained constant unless a change of film failure mode occurred. Adhesion was monitored for 5 years to determine the effect of aging and the results were found to be practically identical over this duration which indicates high film stability.

To improve the coating thickness and process efficiency of conventional laser melt injection (LMI), we introduced laser-induction hybrid melt injection (LIHMI) to prepare spherical WC particle (WCP)-reinforced metal matrix composite coatings on a Ti-6Al-4V substrate. The laser-induction hybrid melt injected coatings were 2.0–2.2 times thicker than that of the conventional laser melt injected coatings. The microstructure and mechanical properties of the WCP/Ti-6Al-4V composite coatings by LMI, LIHMI with induction preheating (pre-LIHMI) and LIHMI with induction preheating and post heating (pre/post-LIHMI) was investigated systemically. LIHMI inhibited the nucleation of primary TiC dendrites in the laser molten pool between adjacent WCP; therefore, the total amount of TiC in the laser-induction hybrid melt injected coatings was far less than that in the laser melt injected coatings. We found that (5.6–5.8)% TiC, β-Ti, and β-Ti/α-Ti formed in the laser-induction hybrid melt injected coatings, while 23% TiC, (Ti,W)C1-X and β-Ti formed in the laser melt injected coatings. In addition, pre/post-LIHMI led to a drastic WCP/Ti interfacial reaction due to the long dwell time and high temperature of the laser molten pool, which greatly deteriorated the mechanical properties of the coatings. Compared with those of the pre/post-LIHMI samples, the pre-LIHMI samples exhibited a shorter liquid residence time and lower temperature of the laser molten pool and a more moderate WCP/Ti interfacial reaction. In addition, tension strength of pre-LIHMI sample and pre/post-LIHMI sample is 34% and 12% higher than that of LMI sample.

The deformation behaviour of particles and substrate in cold spray is dictated by the intrinsic properties of both materials, and their bonding directly affects the resulting properties of the deposited coating. The processing through heat treatment of aluminium alloy powders has only recently been developed for both cold spray and additive manufacturing, hence the necessity to evaluate and further understand the evolution of their properties. In this study, an Al 7075 gas-atomised powder was solution heat treated, quenched and subsequently aged. The powder in its as-quenched, T4 (natural ageing at room temperature for 21 days) and T6 (artificial ageing at 120 C for 24 h) condition was characterised through differential scanning calorimetry and scanning electron microscopy to evaluate the precipitation kinetics. Powders were cold sprayed using heated N2 at 500 C and 6.0 MPa and the resulting deposits were evaluated using tubular coating tensile and pull-off bond strength tests. The precipitation development in the gas atomised powder was found to be similar to the bulk alloys, with development of η′ precipitates during artificial ageing and Guinier-Preston zone formation and development during natural ageing. A relationship between the deposition efficiency of the powders and the coating properties was discovered and explained through an adapted densification mechanism based on powder tamping.

During the hard machining of powder metallurgical high-speed steel, finely dispersed carbides in the steel expose tools to both thermal and mechanical load. PVD hard coatings are used to protect the tools from wear, oxidation and diffusion processes. With regard to mechanical and thermal properties, (Ti,Al,Cr,Si)N hard coatings are advantageous compared to (Ti,Al)N due to their nanocomposite coating architecture. In addition to monolithic (Ti,Al,Cr,Si)N, a bilayer coating with a (Ti,Al,Cr,Si)ON top layer is deposited in order to investigate the influence of oxygen on the interaction with the workpiece during machining. The coatings were deposited in an industrial scale coating unit using a hybrid technology consisting of direct current and high power pulse magnetron sputtering (dcMS/HPPMS). The influence of the oxygen/nitrogen and the aluminum/titanium ratio on the coating as well as compound properties of indexable inserts made from cemented carbide were investigated. Furthermore, the oxidation and the phase stability were investigated. Finally, the coating systems were examined in cutting tests during which powder metallurgical high-speed steel was milled using 6 mm cemented carbide milling tools. The coatings show a fine crystalline morphology with a cubic crystal structure and a smooth surface. For oxynitride coatings, both hardness and resistance against plastic deformation show increased values compared to the nitride coatings. The additional oxygen might lead to a more brittle deformation behavior. The coating with an increased titanium/aluminum ratio shows, on the one hand, the best compound properties. On the other hand, its oxidation and phase stability are lower compared to the coatings with a lower ratio. In contrast to titanium, aluminum forms protective oxide layers which increase thermal resistance. In the cutting tests, the nitride coating shows a slightly higher tool life compared to the oxynitride coating. The tool life of the nitride coating with an increased titanium/aluminum ratio is significantly increased compared to the other coatings.

An automated method for the classification of the adhesion strength of thin PVD coatings applied on hardened steel substrates is presented in this study using deep neural networks. For the determination of the adhesion strength Rockwell-indentation tests were carried out according to VDI 3198. For this approach, pre-trained convolutional neural networks are adapted to classify microscopic images into the expected adhesion classes HF 1 to HF 6 using transfer learning with a dataset of 1650 already evaluated indentation images. The classification performance of the Matlab implemented network models AlexNet, GoogLeNet and inception-v3 is compared with test and verification images of Rockwell indentations. The inception-v3 network shows good accuracy for polished (roughness Sa < 20 nm), hardened steel substrates with deposited thin coatings of a thickness up to 5 μm. The classifications of the implemented models exhibit an agreement of approximately 85–90% compared to human assessment. The evaluation is robust against disturbance variables such as different exposure times, brightness, image contrasting and magnifications. Different image capture devices can be used with no effect on the classification. The networks show promising results for automated industrial applications, such as in-line adhesion control in coating processes, as they do not require human operator support.

Plasma electrolytic oxidation (PEO) is first reported for the non-valve metal of brass. The surface morphology of the PEO-treated brass has been examined, indicating the formation of a porous layer similar to that of PEO of valve metals. Abundant lines of Cu and Zn in the optical emission spectra (OES) of the PEO plasma confirms the participation of substrate in the oxide formation. Plasma electron temperature has been estimated by two-line method based on species of Cu, Zn and H, respectively, and also the Boltzmann plot with multiple lines of Cu I. The temperature lies between ~4393 and ~6911 K. However, the spectral lines of Cu I in ultraviolet region are found to be not suitable for temperature estimation. The coating contains crystalline phases of CuO, Cu2O and ZnO, as well as amorphous SiO2. Tribological tests show that the wear resistance of the PEO-treated brass is nearly ~16 times that of the uncoated metal. The mechanism of the PEO of brass has also been discussed.

The transformation of a hydrophilic surface to a hydrophobic surface due to chemical modification and periodic nano pattern formation on silicon surface by 5–12 keV N+ ion bombardment is reported. The reactive N+ ion bombardment at oblique angle incidence leads to form silicon nitride (Si3N4) on the surface. Also, a periodic wave-like ripple pattern is formed on Si surface at nanoscale range whose wavelength and surface roughness can be regulated by varying the ion energy (5–12 keV). It is found that the contact angle of water droplet on such patterned surface increases with the increase of ripple wavelength and surface roughness. In contrast, the contact angle does not change for the same energy Ar+ bombarded Si surfaces, where such type of surface nano patterns are absent and also surface roughness remains almost the same. The morphologies of the irradiated and un-irradiated Si surfaces are examined by Atomic Force Microscopy (AFM), whereas the surface chemical composition is investigated by X-ray photoelectron spectroscopy (XPS). The chemical modification in terms of Si3N4 formation on the surface, periodic wave-like ripple pattern formation and high increase of root mean square (rms) roughness for N+ bombarded Si surfaces result in hydrophilic to hydrophobic transformation. The tuning of wettability in terms of ion beam parameters for the patterned and chemically modified Si surfaces is discussed in detail.

Adding Si into transition-metal nitride hard coatings is known to enhance mechanical properties and oxidation resistance. At the same time, however, Si promotes precipitation of wurtzite-structure AlN in Ti1-xAlxN during deposition by magnetron sputtering or cathodic-arc-evaporation, resulting in a decrease in layer hardness. Here, we report nanocomposite films of metastable cubic NaCl-structure TiAlSiN deposited using a hybrid approach combining high-power impulse magnetron sputtering (HiPIMS) from an Al target with DC magnetron sputtering (DCMS) from TiSi targets (Al-HiPIMS/TiSi-DCMS) in which a substrate bias is synchronized to the metal-rich portion of each HiPIMS pulse. The Al/(Al + Ti) ratio is varied from 0.26 to 0.77 by adjusting the TiSi target power, while the Si content ranges from 7.6 to 10.3 at.%. Cubic-structure TiAlSiN solid solutions are obtained with a maximum Al/(Al + Ti) atomic ratio of 0.59 and 9.4 at.% Si. Excess Si segregates to grain boundaries to form a SiNx-rich tissue phase. The hardness H and elastic modulus E of cubic TiAlSiN films increase from H = 19.4 ± 1.7 and E = 322 ± 12 for TiAlSiN layer with Al/(Al + Ti) = 0.26 to H = 37.3 ± 1.3 and E = 388 ± 12 GPa for TiAlSiN layer with Al/(Al + Ti) = 0.59. The TiAlSiN films also exhibit a low intrinsic stress (−0.55 to 0.62 GPa), resulting in a combination of properties: superior hardness and low stress.

Due to its biodegradability, Mg has recently been chosen as a potential temporary load bearing implant material. However the corrosion resistance of Mg must be improved to control its degradation rate matching with the bone healing process. One way to solve the issue is to deposit another bioactive and biocompatible hydroxyapatite (HA) coating on Mg implant via electrodeposition. With this motivation, the current paper explores how the current density, a crucial process parameter, influences the formation, characteristics and degradation of HA-coating. Electrodeposition at three different current densities (3, 6 and 13 mA/cm2) was performed on AZ31B Mg substrate followed by an alkali treatment to ensure the complete HA deposition. Surface morphology, chemical composition, crystallinity and texture of the coating were evaluated, followed by a potentiodynamic corrosion tests to assess the degradation resistance of the coated samples. Characterisation results show that low current density of 3 mA/cm2 results in a compact, dense and uniform coating layer as compared to 6 mA/cm2 and 13 mA/cm2. Accelerated H2 gas evolution at Mg cathode and faster deposition at higher current density (of 13 mA/cm2) cause the lack of integration and bonding of crystals, thus resulting in relatively porous, inhomogeneous and rough HA coating. HA coating deposited at low current density is shown to exhibit the best corrosion protection compared to those at higher current density. The findings clearly indicate that the integrity of the coating layer is a crucial quality indicator. Higher current density can produce the coating thickness of as high as 50 μm with appropriate application of the current density followed by alkaline treatment. It is also demonstrated that the electrodeposition could be a promising viable method to fabricate HA-coated AZ31B implants with better and prolonged corrosion protection.

Understanding the growth process and its correlation to the structure of MoSx thin films is essential to control the friction behavior. Nevertheless, structural changes related to kinetic and thermal processes occurring during the deposition are not yet fully understood within the context of MoSx sputtered thin films. Therefore, MoSx films were synthesized by HiPIMS (High Power Impulse Magnetron Sputtering) technique using the one factor at a time method. By systematically changing the bias-voltage (0 to – 200 V), the argon pressure (200 mPa to 600 mPa) or the heating power (0 to 3000 W) the interaction between the deposition parameters and their impact on the structure and the tribological properties was analyzed.The results show significant differences regarding the influence of kinetic and thermal effects. The investigation of the crystallographic orientation by XRD measurements reveals that a high kinetic energy induced by a high bias-voltage favors the growth of the (100) edge plane. A deposition process with a low deposition temperature and thus a low deposition rate leads to a more pronounced (002) basal plane due to the lower surface energy of the (002) surface. A high kinetic energy is also related to a densification of the morphology and a decrease in the sulfur content, which results in a thicker tribofilm and thus a lower wear and friction. Films deposited with a high heating power on the other show a low friction, but at the same time a columnar microstructure and high wear. Thus, the structure affects the amount of generated wear particles during the sliding, but more important is the ability of keeping them in the contact area during the tribotests.

N + Cr ions were co-implanted into the carburized 18Cr2Ni4WA steel to improve hardness, wear and corrosion resistance. The microstructures of the samples were characterized by the glancing incidence X-ray diffractometer, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy, respectively. In addition, the mechanical, corrosion and tribological properties were evaluated by nano-indenter instrument, electrochemical corrosion workstation and wear test, respectively. The results showed that after implanting N + Cr ions, a new nano-nitride phase was formed on the surface of carburized steel. Ions implantation process was accompanied by the radiation damage, which led to lattice distortion on the surface of the steel. These changes accordingly made the N + Cr ions implantation layer present high nano-hardness. Meanwhile, the N + Cr ions implantation layer could effectively prevent the synergistic effect of corrosion and friction in seawater environment, and significantly enhance the tribological property of the carburized steels in simulated seawater.

Laser cladding was investigated as a method for the in-situ synthesis of Ti-Al-C MAX phase coatings due to its speed compared with standard powder metallurgy methods, localized high power density and small heat affected zone. A 2Ti:Al:C coating on a pure Ti substrate was targeted using a stoichiometric elemental powder ratio, resulting in a dense, well bonded composite coating of three layers totalling 1.33 ± 0.02 mm thick. A thin overlayer containing Ti2AlC MAX phase as the majority phase was produced at the coating surface, offering evidence for the feasibility of in-situ synthesis of a MAX phase by laser cladding with an elemental powder feed-stock. Quantitative phase analysis of XRD data indicated that the coating contained Ti2AlC as the majority phase at the coating surface, along with a uniform distribution of TiC0.64, Ti3Al and TiAl. A maximum Vickers hardness of HV 811 ± 11 was observed in the sub-surface region of the coating.

FeCoCrNi high-entropy alloy/WC composite coatings were fabricated via plasma cladding on steels adding different mass fraction of WC. Effects of WC content on the microstructure and mechanical properties of the coatings were studied. The results showed that WC content significantly affected microstructure and the wear resistance of the coatings. With the increase of WC content, the microstructures of the coatings became complex. When WC content was more than 60%, the coatings consisted of WC, FCC phase of HEA matrix as metal bond, Fe3W3C carbide phase and Cr-rich secondary solid solution phase. The Fe3W3C carbides improved the hardness and wear resistance of the coating. When WC content was at a high proportion of 60%, the HEA/WC coating had the best wear resistance with the minimum volume wear rate of 3.27 × 10−7 mm3/N·m and the high hardness of 59.6 HRC, which was better than commercial Ni60/WC coating with the same WC content.

To enhance the corrosion resistance of directional structure coating of Ni60 alloy, the directional structure composite coating of Ni60 alloy reinforced with WC was prepared on the S45C steel by the induction remelting and forced cooling method. The immersion corrosion behaviors of coatings in 10% H2SO4 solution for 168 h and its electrochemical corrosions were investigated to analyze its corrosion resistance. The results showed that WC changed the grain boundary density and grain boundary type, having important effect on corrosion resistance and corrosion mechanism of directional structure Ni60 coating. The corrosion potentials of directional structure Ni60 coating and Ni60/WC coating is −0.395 and −0.112 V, respectively. The corrosion resistance of directional structure Ni60/WC coating is better than that of the coating without WC. The corrosion mechanism of directional structure Ni60/WC coating is slight intracrystalline corrosion, while the coating without WC is the pitting corrosion and the microgalvance corrosion.

Four Ti-Al-N/Ta-Al-N multilayer coatings were developed by a hybrid process combining arc evaporated Ti0.55Al0.45N and sputtered Ta0.57Al0.43N or Ta0.77Al0.23N layers. The two Ti0.55Al0.45N/Ta0.57Al0.43N multilayers have a bilayer period (Λ) of 41 and 25 nm, and the two Ti0.55Al0.45N/Ta0.77Al0.23N multilayers have Λ = 42 and 26 nm, respectively. These are compared with Ti0.51Al0.43Ta0.06N/Ta0.77Al0.23N multilayers having Λ ~40, 33, 25, and 13 nm and are composed of arc evaporated Ti0.51Al0.43Ta0.06N and sputtered Ta0.77Al0.23N layers. The smallest bilayer period of ~13 nm was realised without mechanical shutters, simply by using the two-fold substrate rotation and target arrangement. The alternating growth of Ta0.57Al0.43N respectively Ta0.77Al0.23N layers with arc evaporated Ti0.55Al0.45N or Ti0.51Al0.43Ta0.06N layers allows for full crystallisation in a single-phase face-centred cubic structure, although monolithically grown, these exhibit additional ε-TaN and/or wurtzite AlN-type phases. The mechanical properties of our eight different multilayers indicate a dependence on their bilayer period. Highest hardness (33.6 ± 1.1 GPa) combined with a low indentation modulus (375 ± 9 GPa) could be realised by Ti0.51Al0.43Ta0.06N/Ta0.77Al0.23N coatings with Λ = 13 nm, whereas the Ti0.55Al0.45N/Ta0.77Al0.23N multilayer with Λ = 42 exhibits the lowest hardness (31.1 ± 2.1 GPa) combined with a high indentation modulus (392 ± 25 GPa).

The stability upon air-annealing of uncapped Au-Co thin films is investigated. The analysis focuses on the modifications of the crystalline fraction of the films produced by physical vapor deposition. The film with the highest Au concentration exhibits the strongest diffraction signal, corresponding to a Au–rich fcc AuxCo1−x solid solution alloy, with nanocrystals which have a rod–like shape. Air annealing induces a progressive de-alloying which is complete at 500 ∘C, as shown by X-ray Absorption Spectroscopy and X-ray diffraction. The film, that is directly exposed to the oxidizing atmosphere, undergoes a de-wetting process, likely triggered by Au. X–ray nanoimaging mapping enlightens the presence of interpenetrating sub-μm Au and Co3O4 domains. This peculiar annealed nanostructured system can have interesting applications in the field of catalysis.

Generation of hydrogen using photoelectrochemical (PEC) water splitting has attracted researchers for the last two decades. Several materials have been utilized as an anode in a water splitting cell, including ZnO due to its abundance, low production cost and suitable electronic structure. Most research attempts focused on doping ZnO to tailor its properties for a specific application. In this work, atomic layer deposition (ALD) was used to precisely dope ZnO with hafnium (Hf) in order to enhance its PEC performance. The resultant doped materials showed a significant improvement in PEC efficiency compared to pristine ZnO, which is linked directly to Hf introduction revealed by detailed optical, structural and electrical analyses. The photocurrent obtained in the best performing Hf-doped sample (0.75 wt% Hf) was roughly threefold higher compared to the undoped ZnO. Electrochemical impedance spectroscopy (EIS) and open-circuit potential-decay (OCPD) measurements confirmed suppression in photocarriers' surface recombination in the doped films, which led to a more efficient PEC water oxidation. The enhanced PEC performance of Hf-doped ZnO and effectiveness of the used metal dopant are credited to the synergistic optimization of chemical composition, which enhanced the electrical, structural including morphological, and optical properties of the final material, making Hf-doping an attractive candidate for novel PEC electrodes.

Erosion wear of boiler tubes occurs from room temperature to high temperature and is accelerated by oxidation and hot corrosion above 400 °C temperature. The demand for hard coatings compatible in improving erosion, oxidation and hot corrosion resistance while maintaining the desired mechanical properties of the base material is increasing with the advancement of technology. In this work, WC-12Co coating, Stellite 6 coating and Stellite 21 coatings have been deposited on SAE213-T12 boiler steel using a Detonation gun (D-gun) spray method, and their erosion performances have been evaluated at 400 °C temperature using an air jet erosion tester. The erosion tests have been carried out using the alumina erodent particles at 30° and 90° impact angles. The surfaces of the as-sprayed coatings and the specimens eroded at 400 °C temperature were analysed using a scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS). Stellite 21 coating has shown comparatively lower erosion rate than the Stellite 6 and WC-Co coatings at 400 °C temperature attributed to the formation of protective oxides of chromium and cobalt at 400 °C. The effects of microhardness and temperature on the erosion behaviours of the coatings at 400 °C temperature are discussed. The oxide layers of chromium and cobalt and accumulation of hard phases of nickel, molybdenum and carbon contributed in the protective behaviour of the deposited Stellite 6 and Stellite 21 coatings at 400 °C. The oxidation enhanced erosion wear is observed at 400 °C temperature for all the coatings.

The cross-sectional distribution and focusing properties of intense pulsed ion beam by an active magnetically insulated diode for material modification is presented. The ion beam accelerator BIPPAB-450 uses the surface flashover of polymers as the ion source, generates intense pulsed ion beam composed of protons and carbon ions with a pulse length of 120 ns, ion energy up to 450 keV, energy density up to 3 J/cm2. By the strong flash thermal effects on the surface of materials, the ion beam can be used for the surface treatment and ablation related application. The cross-sectional distribution of the ion beam was measured by infrared imaging method. The results on the focusing of the diode reveal the distribution in the plasma generation on the anode surface. Comparative study on beam focusing during transportation was made and it is demonstrated that by using a copper beam limiter, the maximum beam energy density can be increased by a factor of nearly 1.5. The change in the beam phase-space distribution by the limiter is also exhibited and the influence on beam diagnostics and optimization is discussed reasonably.

This paper investigates damage generation and evolution nearby silicon surface bombarded by energetic carbon ions by using molecular dynamics simulations. We experimentally measured elementary composition in defect regions based on energy dispersive spectrometer analysis. Using molecular dynamics simulations, point defects generation and evolution in monocrystalline silicon were illustrated. The percentage of carbon in defect regions is significantly more than that in non-irradiated regions of monocrystalline silicon. Point defects rapidly generate at the beginning of collision cascades between projective carbon ions and silicon atoms. The radial straggling and penetration along the depth direction are respectively dominant when projective ions with different kinetic energies implant into silicon target. These results can be used to better understand the interaction between projective energetic ions and target.

Titanium nitride (TiN) is a good choice for the improvement in surface hardness of high-speed steel. Unfortunately, it has low adhesion with substrate and exhibits high friction coefficient; as a result it does not provide sufficient protection against sliding wear in metal-to-metal contact. The adhesion problem can be removed by nitriding process, whereas friction coefficient can be reduced by solid lubrication coating. In this study, an attempt is made to synthesize TiN hard coating as well as solid lubrication coating of molybdenum disulfide (MoS2) using magnetron sputtering, along with substrate pre-treatment by cathodic cage plasma deposition using titanium cathodic cage. The cathodic cage plasma nitrided sample exhibits significantly higher surface hardness, which reduced by solid lubrication coating. The nitrided sample depicts the presence of iron nitrides, TiN and nitrogen diffused martensite phases, whereas coated samples shows the presence of MoS2 and TiN phases. The friction coefficient and machining temperature are dramatically reduced by lubrication coating. This study recommends that the use of cathodic cage plasma nitriding using titanium cathodic cage is beneficial for improved surface hardness, and addition of solid lubrication coating is beneficial for reducing the coefficient of friction and machining temperature by scarifying hardness. As, both the systems are already proven to be appropriate for industrial-scale uses, thus results from this study can be applied for industrial-scale application.