Structured surfaces with anti-wetting character are used in various fields such as aeronautic, textile or food industries. Enhanced fluid mechanical properties guaranteeing laminar air flow, the prevention of ice-accretion on antennas, stain-resistant textiles and anti-bacterial coatings are just a few examples for their applications. These surfaces have often been inspired by nature. Lots of research have therefore been focused on mimicking unique natural properties like the famous lotus effect in order to transfer it to technical scale. Water droplets on lotus leaves roll off easily and by that, carrying dust away. In practice, this mechanism is used for solar cells in order to enlarge their efficiency. A highly water-repellent surface is essentially characterized by the combination of a randomly distributed binary structure and a low-surface energy material. The techniques for the preparation of non-wetting surfaces include templating, lithography, sol-gel, chemical etching, plasma, etc. This paper provides a review of structured surfaces for specific applications in the fields of anti-icing, fluid mechanics, and anti-corrosion. The focus lies on the development of surfaces with low wettability and improved corrosion resistance that possess a binary roughness in the micro and nano-scale.

A glimpse of the current industry efforts in using cold spray coatings, in repair and refurbishment of structural gas turbine components will be presented. One of them makes use of the cold spray coating process as an alternate to conventional welding, for refurbishment of Oil and Gas components. The technology from a coupon level to a component level, using the new spray on welding process of repair, was developed and industrialized. Detailed characterization of the cold spray coatings, in terms of the bonding mechanism and thermal stability, along with correlations between the residual stress and fatigue behaviour, will be presented, for a variety of hard Superalloy coatings, for various repair applications.

This study reports a fabrication of TiO2 on the surface of dental implants by pulsed D.C. magnetron sputtering from a Ti target. A systematic investigation on the microstructure and mechanical properties of TiO2 films was carried out with the variation of O2 contents and substrate temperatures. The effects of deposition parameters on the fabricated structures were investigated by X-ray diffraction (XRD) technique and field emission scanning electron microscope (FE-SEM). Hydrophilic properties were evaluated by measuring water contact angles on the film surface. By increasing O2 contents up to 40%, surface roughness of TiO2 film increased while a relatively smooth surface was obtained with 50% O2 contents. Surface roughness and adhesion strength both increased as substrate temperature increased up to 200°C. From these results, hydrophilic and adhesive properties of the present TiO2 films synthesized with 40% O2 at 200°C regarded to be suitable for biocompatible applications.

The major objective of this paper is to present the methodology of sample preparation for duplex structure thermal barrier coatings (TBCs). The analysed TBC structure consists of metallic, nickel aluminide (NiAl) bond coat, deposited during chemical vapour deposition (CVD), and ceramic yttria partially-stabilized zirconia (YPSZ) top coat. The comprehensive procedure of sample preparation, including casting, turning, heat treatment, cleaning and polishing, also both deposition processes, were conducted in the Research & Development Laboratory for Aerospace Materials at RUT.
In order to provide maximum adhesion between layers, a polishing process of substrate and bond cold is applied. In case of flat samples, the polishing can be carried out on a disc polishing machine, however, for complex geometries (cylindrical samples, turbine blades), it has to be carried out differently.
The authors will utilize the centrifugal tumbler to remove the near surface sample layer (elimination of casting defects) and polish its surface. The CNC controlled sander customized for four-axis automatic blasting is used to obtain proper surface finish of bond coat (US4321310).

The development of modern science and technologies increases the demand on the materials used. The use of different aircraft engine components and materials structures in aggressive environments or elevated temperature necessitate improvement of existing and development of new materials. They should be characterized by ease of production, high performance and physicochemical properties. An important role in this field also concerns appropriately selected protective coatings and modification of surface layer that significantly affect the range of applicability. They are designed mainly to improve wear and corrosion resistance in elevated temperature of operation. The tendency in the development of surface layer engineering are thin coatings, based on small range diffusivity and pure coating systems. The development of new types of these materials systems will not only increase the efficiency of conventionally used elements but also introduce new procedural methodology for aviation industry. More and more attention in the field is paid to PVD techniques. The presented paper focuses on new types of materials systems obtained with this method. The authors focused their study on investigation of coatings of TiN, TiAlN and TiCN types and their impact on properties of titanium Grade 2 as a substrate. This material is conventionally used for production of aircraft engine compressors blades and is an excellent example for modification of elements performance parameters. Different coatings obtained on the same substrate allowed investigation of their impact on corrosion, erosion and wear resistance. Additionally, complex microstructure investigation has been performed in meaning to describe the substrate-coating materials system characteristic.

Polyetheretherketone (PEEK) coatings were electrophoretically (EPD) deposited on the near-beta Ti13Zr13Nb titanium alloy. Suspension composition and EPD parameters were investigated in detail. Post heat treatment was performed to improve the adhesion of the as-deposited coatings to the underlying substrate. A microstructure of the titanium alloy and the coatings was investigated by light microscopy, scanning and transmission electron microscopy as well as by X-ray diffractometry. Atomic force microscopy was used for investigation of surface topography of the coated alloy. It was found that the 60-70 microns thick coatings were semi-crystalline and homogeneous, without any cracks or voids. Micro-scratch tests revealed a very good adhesion of the heat treated coatings to the Ti13Zr13Nb alloy. The friction and wear properties of the uncoated and coated alloy were evaluated using a ball-on-disk apparatus at unlubricated contact. The coating essentially improved the frictional wear resistance and decreased a coefficient of friction of the titanium alloy substrate. This work showed that EPD is a very useful method to deposit uniform polymer PEEK coatings on near-beta titanium alloy substrate for tribological applications.
ACKNOWLEDGMENTS
This work was supported by the Polish National Science Centre (decision no. DEC-2013/09/B/ST8/00145). A part of this study (tribological tests) was supported by the AGH-UST (project no 11.11.110.293).

Steady-state fluorescence (SSF) technique in conjunction with UV-visible (UVV) technique, atomic force microscope (AFM) and scanning electron microscope (SEM) was used for studying film formation from TiO2 covered polystyrene (PS) latex particles. The effects of TiO2 content, film thickness and PS particle size on the film formation and structure properties of PS/TiO2 composites were studied. For this purpose, in the first part, two different sets of PS films with thicknesses of 5 and 20 μm were prepared from pyrene-(P-) labeled PS particles (320 nm) and covered with various layers of TiO2 using dip-coating method. These films were then annealed at elevated temperatures above glass transition temperature (Tg) of PS in the range of 100–280 0C. Fluorescence emission intensity, Ip from P and transmitted light intensity, Itr were measured after each annealing step to monitor the stages of film formation. The results showed that film formation from PS latexes occurs on the top surface of PS/TiO2 composites and thus developed independent of TiO2 content for both film sets. But the surface morphology of the films was found to vary with both TiO2 content and film thickness. After removal of PS, thin films provide a quite ordered porous structure while thick films showed nonporous structure. In the second Part, two film series were prepared from PS particles with diameters of 203 nm (SmPS) and 382 nm (LgPS) by covering them with different layers of TiO2 and annealed them at elevated temperatures. Results showed that SmPS/TiO2 films undergo complete film formation independent of TiO2 content. However, no film formation occurs above a certain TiO2 content in LgPS/TiO2 films. SEM images showed that SmPS/TiO2 films have highly well-ordered microporous structures with increasing TiO2 content after extraction of PS polymer whereas LgPS/TiO2 composites show no porous structure for high TiO2 content. Our experiments also showed that porous TiO2 films with different sizes could be successfully prepared using this technique.

Titanium-based nitride coatings exhibit peculiar properties at elevated temperatures which make them relevant candidates for various high-temperature applications, in thermal solar energy converters as a highly stable plasmonic absorder, in biomass energy converters as catalyst to fasten the hydrocarbons pyrolysis process in view of reducing the formation of polyaromatic hydrocarbons and soot, in generic applications for which thermal conductive coatings with high resistances to oxidation and high hardnesses are mandatory.
Vapor deposition processes are the common processes to manufacture coatings made of Titanium-based nitrides. Nevertheless, those processes exhibit two main drawbacks, maximum coating thicknesses limited to a few micrometers on the one hand and a rather low deposition rate (i.e., a few grams per hour) on the other one.
On the contrary, plasma spray processes allows manufacturing thick coating (i.e., a few hundreds of micrometers) at a relatively elevated deposition rate (i.e., a few kilograms per hours). Nevertheless, those deposition processes are unsuitable for processing incongruent materials, such as nitrides.
A solution relies in the formation in situ of those materials, in other words in alloying the metallic feedstock with Nitrogen during deposition. This corresponds to a so-called reactive deposition process. Several attempts were made during the 90's, and since then, to manufacture such coatings by implementing an atmospheric plasma torch equipped with a shroud into which the nitriding reaction can take place. Such an approach, up to now, has never been fully successful: the complex fluid dynamics within the shroud together with the necessity to cool it down made those systems difficult to operate (i.e., clogging, etc.) and never allowed to alloying the in-flight particles in a large extend since the chemical interaction occurs at the periphery of large molten particles, a process known for being inefficient from the thermodynamic point of view. The very low pressure (i.e., in the range of 50 to 150 Pa) plasma spray process allows manufacturing metallic coatings by condensation of vapors resulting from the full or partial vaporization of feedstock particles in the core of the plasma flow. The strong expansion of the plasma, under such a low pressure, allows carrying the vapors over long distances (i.e., > 1 m). This physical state (rather high enthalpy, gaseous species, etc.) together with a long interaction time due to the plasma plume length can promote the chemical reactivity. Several research institutes consider nowadays this second approach as a more relevant one.
This paper aims at presenting recent results with the primary goal of better understanding physical mechanisms occurring during the reactive deposition process of Titanium with Nitrogen. Optical emission spectroscopy was implemented to better identify the reactive mechanisms. Coatings, with up to 25% at. of Nitrogen, were manufactured and their structure was evaluated in terms of phases content (XRD), Nitrogen content (GD-OES), as well as hardness values. TiN and TiN0.3 nitrides were identified in the coatings and are formed in- flight by gas-gas reactions. Ti2N nitrides were also identified in the coatings and are formed by solid-gas reactions.

Using surface coverage technology of hot-dip aluminized prepared Fe-Al alloy coating on the surface of 45 steel substrates and then double glow plasma surface modification technology with alloying Nb was employed to prepare the Fe-Al-Nb alloy coating on the surface of Fe-Al alloy coatings. Firstly the microstructure's composition distribution and organization structure of the Fe-Al-Nb alloy coating were characterized by scanning electron microscope (SEM)energy dispersive spectrometer (EDS) and X-ray diffraction (XRD), and then the high-temperature oxidation resistance properties of the alloy coating prepared under optimal conditions deeply through the experiments of isothermal oxidation were researched and analyzed.
The results showed that the optimal process parameters were as follows: source electrode voltage 800V~900V, substrate electrode voltage 350V~450V, operating atmospheric pressure 35Pa~45Pa, inter-electrode distance 20mm, testing temperature 900a„ƒ~1000a„ƒ and soaking time 3h Fe-Al-Nb alloy coating surface was flat and compact, which was mainly composed of simple substance Nb, the other hard phase AlNb2-Fe7Nb6-Fe2Al5 and Fe3Al etc. dispersed in the surface layer which increased the surface hardness significantly. The thickness of coating was about 150µm in the diffusion layer, Al concentration exhibited gradient distribution, decreased gradually away from surface, Fe concentration was about 45wt%, both of them formed the ductile Fe3Al and FeAl phases which contained 1.5wt%~2wt% Nb in the form of dispersed second-phases. During the 100-hour isothermal oxidation experiments at the temperature of 600a„ƒ and 700a„ƒ, Fe-Al-Nb alloy coating surface formed a compact oxidation film, its high-temperature oxidation resistance increased dramatically as compared to the Fe-Al alloy coating and substrates.

In this work, the effects of pulsed plasma nitriding on HVOF-sprayed martensitic stainless steel were investigated. Martensitic stainless steel was pulsed plasma nitrided at 793 K under 0.00025 MPa pressure for 43200 s in a gas mixture of 75 % N2 and 25 % H2. The pulsed plasma nitriding resulted in not only an increase in the surface hardness, but also improvement of wear resistance of the HVOF sprayed stainless steel coating because of the CrN, Fe3N, and Fe4N phases. However, the corrosion resistance of the HVOF-sprayed martensitic stainless steel decreased notably by nitriding process.
Key words: HVOF spray coating, pulsed plasma nitriding, martensitic stainless steel, wear, corrosion

The article describes the role of the nitrided layer in the properties of the coating /substrate systems. In the present study, samples made of AISI 4140 steel pre-treated with gas nitriding and coated with different PVD coatings (multi-module CrN/CrCN coatings and gradient CrN/CrCN coatings) were investigated in terms of adhesion and wear resistance. To examine the influence of the nitrided layer on the performance of the coating's substrate composite, coatings were deposited on not nitrided and on nitrided samples, prepared under different nitriding conditions.
Particular on the basis of studies, It was showed that the effect of nitriding process cannot be reduced only to increase the hardness of the substrate, ie., to reduce the differences in hardness between the coating and the substrate. As indicated, the nitrided layer, which is characterized by a gradient of hardness and Young's modulus PVD coating reduces brittleness observed in the study of Daimler-Benz.

Fe-Al-Cr alloyed layer was deposited onto the surface of Q235 low carbon steel via double glow plasma surface metallurgy technology to improve its wear resistance. The microstructures, phase constitutes, composition distributions and microhardness were determined.The tribological properties of Fe-Al-Cr alloyed layer were tested on a ball-on-disk tribometer by rubbing against GCr15 and silicon nitride (Si3N4) balls at room temperature and high temperature (i.e. 250A°C and 450A°C), respectively. The results indicated that the alloyed layer was 25 Aµm in thickness, which was homogeneous and compact, and it showed metallurgically adhered to the substrate. The main phases of the alloyed layer were Fe2AlCr, Fe3Al, FeAl, Fe(Cr) sosoloid, Cr23C6 and I±-Fe(Al).According to the frictional wear tests, the frictional coefficientand specific wear rate of the Fe-Al-Cr alloyed layer were all lower than those of the substrate under room and high temperature. The special wear rate of treated specimen at 450A°C was 2.524A—10-4mm3 N-1 m-1, which was only 45.2% of the untreated specimen.

We propose an experimental study of the surface to dry and analysis of the evolution parameters roughness. The simplified model was proposed to predict the metrological parameters in the contact area of the deformed surface. The model is based on the analysis of the topography 3D of the deformed surface. The hot isostatic pressing (HIP) is the only process that will develop fully dense samples, from Fe,Cr,Mo,Ni,Ti,W powder. This sample is hot pressed at 1500A°C under 150Mpa of argon pressure. Moreover, the grain size of the consolidated samples was analyzed by SEM, ABSD and optical microscopy. The study aims to characterize the topography of sintered materials obtained by wear tests. Therefore, it is interesting initially in the evolution of wear for the loads applied and to characterize the different roughness emerging from 3D AFM observations. Experimental and theoretical research on the topography changes during dry contact deformation was carried, providing results that demonstrate the persistent nature of roughness asperities even under high loading when bulk plastic deformation appears. Most theoretical investigations of the problem have been based on a simplified model neglecting the statistical distribution of asperities on the real surface, used test and 3D measurement of surface topography in order to investigate its frictional behaviour. The mechanism of contact of a rigid plane with a rough surface in the presence of a lubricant is different than in the case of dry contact. The topography of the samples was measured both in initial undeformed and in the deformed state after removal of the load. In these states, however, a change of the shape of the samples when compared to the initial state was observed. Thus, prior to the determination of roughness parameters of the deformed surfaces, their curvature was removed using a filtration procedure. The essential differences in surface topography of samples loaded in dry condition are confirmed in the analysis of roughness parameter evolution. The following 3D parameters were considered: In the unloaded state, flattened asperities can be observed on the deformed surface. The real contact area corresponding to the maximal load attained in the surface compression experiment can be identified from measurement of the deformed roughness after unloading. The identification of the real contact area was carried out using a special algorithm based on single profile analysis. It should be noted that the profiles obtained in this way have a common reference level. The selected profiles also have the same direction, which, in the case of anisotropic surfaces (turning, grinding), should be perpendicular to the direction of the movement of the machining tool. The proposed model was applied to analyze a wear of four kinds of rough surfaces. The predicted values were compared with experimental results. The wear and surface roughness based on the parameters of dry friction tests were measured. This study suggested the optimal parameters of chemical composition, and analysis of the effects alloying elements on surface roughness and wear in the process dry friction tests.

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