Seznam abstraktů 2015: SEKCE D - MODERNÍ TRENDY V POVRCHOVÉM INŽENÝRSTVÍ

In industrial practice on various production stages of the fittings for overhead power line, there are many factors that cause the zinc coating thickness diversification, that in the next step determine its corrosion resistance. This effect is observed especially in the thermal cutting process. The changes in the structure of the cut material influence the structure and properties of zinc coatings.
The paper presents the results of investigation regarding the typical production process of fittings for overhead power lines (double-eye links). The research was conducted on the link’s flat surface (after rolling) and the side surface (after cutting). The zinc coatings thickness and structure diversification were evaluated on the basis of metallographic analysis and corrosion tests (according to PN-EN ISO 9227).
It has been proved that the existence of HAZ in the oxy-acetylene cutting material and, as a consequence, bigger hardness have an impact on the diffusion pace on the edge of steel/coating, and on the processes of substrate melting which assist zinc coating growth.

Cr2N0.62 - 11Ag nanocomposite coatings, containing 11 wt.% of Ag solid lubricant, were deposited on substrates made of Cr-V ledeburitic tool steel Vanadis 6 by reactive magnetron sputtering at a deposition temperature of 500 °C. The experiments consisted of long term annealing up to 24 h at elevated temperatures of 300, 400 and 500 °C in closed-air atmosphere. The structural changes after long time annealing were evaluated by Auger electron spectroscopy (AES) and scanning electron microscopy (SEM). As a result of silver diffusion, the higher population density of silver particles on coating surfaces has been detected after 0.5 h and 2 h, respectively, annealing at 400 °C and 300 °C, respectively. Maximum was found after annealing at 300 °C / 2 h. Nevertheless, in certain point the population density of silver particles decreased with increasing annealing time. Moreover, during annealing at temperature of 500 °C, very low population density was observed through all annealing process. This phenomenon was explained by sublimation of very small silver particles (less than 20 nm) and also by oxidation of coating surface, which was detected mostly during annealing at 500 °C. The oxide layer seems to be effective as a barrier of silver diffusion. The annealing of the films at temperatures below the deposition temperature induced limited silver diffusion and depletion of silver within coating matrix.

Corrosion failure of metallic electroplated coatings on various products were analysed and the dominant corrosion stimulators were identified. The thickness and porosity of coatings are very important for their corrosion resistance. The suitable thickness of these coatings shall be chosen from the technical standards recommendations depending on the severity of service conditions. This characterisation of corrosion risks are not fully respect in other products standards, e.g. for electronic products, devices and installations. The corrosion caused the failure of these items. In articles the examples of how different of environment fit into the corrosivity classification system are given.

The study presents the results of the corrosion resistance and bacteriological research of steel DC01 protected by a-C: H, CrN and TiN / TiAlN coatings, that were produced by PVD method.
The experiment was divided into two stages. The first part was concentrated on the corrosion resistance of analyzed coatings affected by selected endobiotic and body liquids (Ringer’s solution and artificial saliva) and Domestos solution. The second part assessed bacteriostatic or bactericidal properties of two strains of bacteria - Pseudomonas aeruginosa and Staphylococcus aureus. It has been proved that the coatings used in the study present good corrosion resistance and bacteriostatic properties.

Simulation of corrosion resistance of steel with polymer coatings has been performed by means of the Monte-Carlo method [1] on the base of the three-dimensional lattice model of polymer system with orientation interactions [2]. The interaction energy of the oxygen with the neighboring eight units of the polymer chains and electric double layer on metallic surface were being accounted. The movement of charged particles was calculated according to the laws of statistical physics and based on checking energy advantage of its position. The developed method allows calculating the number of charged particles passing through the polymer film and reaching to the surface of the metal sheet.
The dependences of conductivity on temperature, film thickness, and the distance between the molecular layers are obtained. It is shown that there is an optimum film thickness at which it is protecting. The adequacy of the developed mathematical models and theoretical curves has been verified by comparison with the data of laboratory and production testing.
References
[1] Mitsutake A., Sugita Y.,Okamoto Y. Generalized-Ensemble Algorithms for Molecular Simulations of Biopolimers. Biopolimers. 2001, Vol. 60, pp. 96-123.
[2] Petrova T., Maksimova O., Maksimov A., Nastuljavichus A., Baruzdina O., Baidganov A. Computer simulation of phase transition, oriental order and mobility in low- and highmolecular ferroelectric nano-systems. In Abstractbook «Technical Proceedings of the NSTI Nanotechnology». Conference and Expo, NSTI-Nanotech. Washington. 2013, pp. 611-614.

The technology of Laser Surface Remelting (LSR) is used to modify the surface layer of bulk materials or coatings in order to improve their surface properties, usually wear resistance. In the case of thermally sprayed coating, its application leads to elimination of porosity and internal oxides on the coating splat boundaries. The increase of corrosion resistance and inner cohesion strength of the coating is expected as a result of laser post-treatment. In the paper, the Co-Cr-W HVOF sprayed coating was subjected to the series of LSR procedures with varying laser parameters to study their influence on the thickness of remelted layer. The laser power and processing speed was the main studied parameters. The optimal parameters for LSR of coating with given thickness were found. Besides the laser parameters, the influence of spraying procedure, namely the procedure of grit blasting, on the creation of cavities in the remelted coating is discussed.

In the study the research findings, regarding the application of innovative solutions from the field of the material science and medicine in the interior of modern ambulances, are described. VentureShield™ VS 7510 E film (I and II grade) was evaluated from the point of view of high sterility level of the interior of an ambulance. The examinations were divided into two stages. Firstly, a degree of the adhesion of chosen kinds of the bacterium e.g. Enterococcus faecalis and Pseudomonas aeruginosa was evaluated. In the second stage, samples toxicity tests were conducted using the mouse fibroblasts cells (NIH/3T3) according to ISO 10993 and ISO 7405 standards (2009). It has been proved that VentureShield™ VS 7510 E film (I and II grade) effectively protects against bacterial adhesion and it is not toxic to living cells, such as mouse fibroblasts. Thanks to that it may be assumed that the film will fulfill its protective function in sanitary ambulances.

In this investigation, Mg-based biodegradable implant with controlled porosity and micro-textured surface was designed and manufactured by using powder metallurgy (P/M) route. Mg powders with different size distribution were compacted under three different compaction pressures (150, 200 and 250 MPa) at 150ºC for 1 min. Compacted green plates were sintered to improve mechanical properties of Mg plates at 380, 400 and 420ºC for 60, 180 and 300 min. This study was aimed to determine an optimal window of pressure, temperature and time to manufacture Mg implants with necessary levels of porosity and strength for eventual biocompatibility and biodegradability tests. The results proved that compaction load had a significant effect on the bending strength. Moreover, it can be concluded that porous Mg based biomedical implant was feasible because of near net shape production with acceptable mechanical integrity.

The influence of surface preparation on the structure of zinc layer has been presented in the paper. Research was focused on barrier dampers made of cast iron. The prepared materials were subjected to a surface treatment: turning, grinding, sanding, grinding and high temperature oxidation. Galvanizing process was carried out by immersion in a bath of zinc and galvanic. The effects were evaluated on the basis of metallographic analysis, evaluation of surface roughness and corrosion tests. It was founded that structure of galvanized layers – phase alloy and zinc are in direct correlation with a surface preparation and a corrosion resistance. Examinations described at the work confirmed the thesis in relation to treating the high-temperature process of oxidizing, not as the kind of the corrosion, but as the manner of preparation of the area facilitating the process of the galvanizing of the grey cast iron.

Metals and their alloys are often used in the production of implants or stents, and are applied to a living organism. For this application it is necessary to provide for biocompatibility, i.e. determine the likely response of the organism to the embedded metal material. Reactions of cell populations in vitro or ex vivo are primary biocompatibility tests. Determination of cytotoxicity is inefficient for these purposes, it is necessary to find out the degree of tolerance of the cell population to the implanted metallic material before the subsequent tests are conducted on experimental animals. The peak of the pyramid are special test trials in patients with allergy to some of the components of the selected alloy. In the statement we deal with reaction of animal cell lines to certain metals and alloys used in medicine that are examined in the system of time-lapse mikrophotography of live cell populations in vitro. Cell lines are scanned in the direct contact with a metal, possibly metal alloy for 72 hours, and subsequently the direct reaction of biocompatibility is evaluated.

The purpose of protective coatings is not only to provide the protected material a new, attractive design, but also new properties, longer durability, corrosion resistance, resistance to specific environments etc. These advantages of protective coatings are used in various branches of engineering, for various corrosivity of the environments, for different types of substrates, etc. The subject of this paper is on the type of substrate, which researched protective properties of the innovative thin coating applied to the non-ferrous substrate. Transparent waterborne coating containing nanoparticles was used for experimental work, which was applied to two types of non-ferrous materials. These non-ferrous materials are the most widespread in technical practice and in conjunction with the advanced technology of protective coatings containing nanoparticles makes this issue very topical. Present experimental results show us a significant potential for industrial use.

This research deals with the influence of thermally sprayed HVOF (High Velocity Oxygen Fuel) coatings on fatigue life of components. HVOF coatings are now a widespread technology commonly used for additional treatment of component surfaces. The advantages particularly consist in achieving of low coating porosity, high adhesion to the base material and residual compressive stress in the surface coating layer. The main application areas of HVOF coatings are applications requiring high surface hardness and wear resistance (pistons, rods, cylinder presses, etc.). Two coatings were evaluated in this study - carbide based coating (CrC-NiCr) and alloy based coating (Stellite 6). The tests were carried out at room temperature and at 600 °C. The main contribution of this paper is to evaluate the coating influence on fatigue properties of coating-substrate system in comparison with the fatigue properties of the substrate itself. In particular, it was examined whether and how the increase or decrease of fatigue properties occurs in this system. The obtained results prove that both evaluated coatings reduce overall fatigue resistance; however, by Stellite 6 coating is the reduction of fatigue properties is not so noticeable.

In this paper, were determined the effects of cutting tool coating material and cutting speed on cutting forces and surface roughness based on Taguchi experimental design method. Main cutting force, Fz is considered to be cutting force as a criterion. In the experiments, depending on the tool coating material, lowest main cutting force is found to be 548 N with KC9240 CVD coated cemented carbide and Lowest average surface roughness (0.812 μm) with KT313 uncoated cemented carbide insert both at 100 m/min. The effects of machining parameters were investigated using Taguchi L18 orthogonal array. Optimal cutting conditions were determined using the signal-to-noise (S/N) ratio which is calculated for average surface roughness and cutting force according to the "the smaller is better" approach. Using results of analysis of variance (ANOVA) and signal-to–noise (S/N) ratio, effects of parameters on both average surface roughness and cutting forces were statistically investigated. It has seen that while cutting speed and cutting tool has higher effect on the cutting force, the cutting tool and cutting speed has higher effect on average surface roughness. The results obtained indicated that CVD cutting tools performed better than PVD and uncoated cutting tools according to cutting forces, but in terms of surface quality was observed poor performance with KC 9240 and KT315 by current parameters.

In surface treatment are often used coatings based on Ni. Their properties include significant corrosion resistance, hardness and abrasion resisant. In this paper we attempted to measure the shock resistance of these layers using the method of impact test. This method offers a simulation of very intensivee local loads that occur mainly during overload and violations.

In this study, glass surface is coated with thin films of TiO2 by using sol-gel route. TiO2 chemicals were used as precursors at the solutions prepared for film coating, and also methanol and acetyl acetone were used as solvent and chelating agent respectively. After the glass samples were dipped in to prepared solutions by using a special apparatus, they were taken into the preheated (500 °C) vertical furnace to dry, and then they were annealed at the same temperature. The thin films formed on the glass surface were characterized through the instrument of X-ray photoelectron spectrometer (XPS), thermogravimetric and differential thermal analysis (TG-DTA), Ellipsometer and Spectrometer test devices. Wet angles of thin films coated with different dipping number and annealed at different temperature, were measured by dropping 1 microliter distilled water (UP_ ultra-pure). The water contact angle between the droplet and the surface of the sample was measured. Wet angle did not change with the number of dipping number. However, the angle of contact change with the temperature of crystallization. Finally, the TiO2 thin film coated glass samples were subjected to soot with the flame of a candle with a special apparatus. After sooting, TiO2-coated glass samples were subjected to UV light for 24-48-72-96-120 hours. UV exposure samples were pictured with same conditions in every 24 hours. Cleaning affect of the surface were identified in a visible way.

The high efficiency of the polymer coating is achieved only by the proper choice of thermal and other conditions during the formation of its structure [1]. The aim the work is to study only the initial stage of physical and chemical processes by the formation of the structure of polymer coating, namely, the creation of a primer adhesive layer after the application of monomer paint solution on the steel sheet before to the polymerization.
In this work, the dynamic Monte Carlo method for the modified lattice Langmuir’s model of adsorption was used. Time dependences of the sticking coefficient of monomers on the surface of the steel at the same and different heating rates of the metal sheet and the given values of the interaction constant of the monomers and the energy barrier are calculated. It’s shown that there is an optimum temperature regime at which the adhesion of monomer coating on the surface of the metal sheet is maximal. The simulation results are confirmed by experimental data [2] on study of adhesion strength of the primer layer from the poly-vinyl-butyral on the surface of steel sheet.
References:
[1] Yilgor I 2013 Proc. 12-th Int.Conf. “Polymers in advanced technologies”(Berlin) p 34.
[2] Yakovlev АD 2008 Chemistry and technology of paint coatings (St.Petersburg – Chemistry)

The paper summarizes the result of laser cladding experiments design to observe the influence of single track overlap. The system combining solid state disc laser with power up to 5,3 kW and cladding head with coaxial powder feeding was used. Powders used in experiment were stainless steel 316 L and Stellite 6. In previous work the single track geometry was discussed, now the different values of single track overlap were tested. The goal of the work is to determine the influence of overlap to coating properties and choose suitable overlap for further experiment. The geometry and mechanical properties of final coatings is discussed.

Laser surface texturing (LST) is an emerging effective method for forming surfaces with specific parameters: optical, electrical, tribological, hydrophobic or hydrophilic and so on. The LST is laser parameters and overlap sensitive process. The new shifted LST is introduced, where heat load by laser picosecond pulses is decreased by specific schedule of scanning. Moreover, the shifted LST gives possibility to increase scanning repetition rate without heat accumulation effect. In this paper we have compared results of application classical methods of LST with shifted LST on stainless steel AISI 304L, 2017 aluminium alloy and nickel-based super-alloy AM1.

In the work fasteners - screws M8*80 made of carbon steel 23MnB4 were being examined that are conventionally protected against the corrosion by zinc galvanizing. The research aim was to compare the lifetime/effectiveness of different zinc coatings (galvanic, hot-dip and lamellar), as the anticorrosion protection of steel fasteners. The first research stage consisted in determination a point of reference - kinetic of the screws corrosion process without a protective coating in the climatic chamber, in neutral salt fog according to PN-EN ISO 9227. Both loss of mass and pitch diameter reduction were measured. Next, a change of mechanical properties was determined performing the static tensile test using samples taken after the individual stages of experiment (0h; 360h; 624h, 744h, 888h, 1000h). Additionally to enable the more detailed description of the kind and the mechanism of the corrosion from studied fragments of elements the metallographic microsections were prepared, on which microstructure and hardness changes were determined. The conducted tests showed that the examined corrosion process apart from essential changes of mass caused also the significant reduction of mechanical properties. In further research the influence of individual types of zinc coating on the kinetics of corrosion process will be presented.

Research were focused to different zinc coatings quality put on iron alloys (cast iron, steel). In the paper the galvanic, hot-dip and lamellar zinc coatings were compared. The complex investigation method consisted in proper coating preparation (in industrial conditions) on specially prepared samples and evaluation of surface state/topography that has essential influence on other coatings specific properties, like corrosion resistance, wear resistance, resistance to mechanical damage, etc. Additionally also mechanical, tribological and anticorrosion properties were determined (in other paper). For surface/topography state evaluation three different methods were used: contact profile recording instrument Perthometer Concept (MAHR) with 3D software, PhaseView optical assembly for 3D surface scanning and MarSurf WS 1 – the high-precision, non-contact measurement of surface texture using the principle of white-light interferometry. During tests the basic parameters describing roughness and waviness together with isometric surface image were determined. Advantages and disadvantages of each method were compared. It was stated that although the most precise results are achieved by contact profilometer application also using the ZeeScan system enable the reliable surface evaluation but in much shorter time.

The inclusions size in context fatigue properties of plasma nitriding steel was studied. The size of inclusion, such as geometry and location, has remarkable influence to fatigue properties of steel 41CrAlMo7-10. The samples were shaped by turning operations and subsequently grinded to prescribe values of a standard test bars. Next technological operation was heat-treatment, such as normalizing, quenching and tempering. Plasma nitriding technology as a diffusion technology was used for applies of nitrided layers on heat-treated material. Plasma nitriding technology is effective method usage in practise especially in order to increase the surface hardness, corrosion resistance and fatigue strength. The samples were subjected to the fatigue bending rotation tests.

In rockets, the heat fluxes that can pass through the wall are among the highest in engineering, fluxes are generally in the range of 1-200 MW/m^2. The strongest heat fluxes are found at the throat, which often sees twice that found in the associated chamber and nozzle. This is due to the combination of high speeds (which gives a very thin boundary layer), and although lower than the chamber, the high temperatures seen there. For this reason, some coolant methods are invented (ablative cooling, radiative, regenerative ….) to protect the nozzle’s body in order to have a long life time of it.
In all cases the cooling effect that prevents the wall from being destroyed is caused by a thin layer of insulating fluid that is in contact with the walls that is far cooler than the combustion temperature. Provided this boundary layer is intact the wall will not be damaged.
This work represents a numerical investigation of effect of a compressible flow on the divergent walls of the nozzle BKE-DLR, representing a laboratory scale model of the Volvo nozzle of the European Vulcain cryogenic engine 2, where we did inject the H2 , with a temperature of T=294.25 °k directed with an angle almost tangent to the wall of the nozzle at the divergent part ( almost 21°) , in order to see the cooling efficiency on the walls & compare it with the case of the absence of H2 injection.

This article deals with morfology of nitrided surface in inner part of cavity. Experiments are focused on creation of clusters of nitrogen on the surface of evaluated material. Peculiarity of this experiment is created sophisticated technological process suitable for creation of nitrided layers inside cavities with really small diameters. The conditions of process are designed to provide strictly defined nitride layers about defined parameters. In this case the Nitrided layers were applied to bars of steel 32CrMoV12-10 which were subsequently evaluated by metallographic, GDOES, XRD microanalysis and microhardness methods. The results of measurement showed trends of chemical composition of alloying elements after chemical-heat treated process through the length of cavity. Plasma nitriding process was applied for increasing of surface hardness of material in deep cavities. In the evaluation of surface structure the new typical marks on the surface of material after plasma nitriding process were found. Mechanical properties of evaluated material were significantly increased.

Hardening of contact surfaces of milling head is centerpiece of this study. The most important point is to maintain defined processed part geometry. This precise processing was performed using the scanning laser hardening method. The scanning method uses a small laser spot in combination with a scanning head. The method is based on a very fast laser beam sweeping perpendicularly to the main laser treatment trajectory, allows better control of energy distribution and optimization of treating pattern. Disk laser with maximum power of 5.3 kW was used for heat treatment. Surface hardness and depth of hardened layer were evaluated. 3D profiles of hardened parts were measured on 3D scanner Alicona before and after laser processing. Geometrical deformations were assessed using the method of differential analysis.

Cathodic protection is especially applied to protection of coating fault on a buried pipe line in soil. According to some authors, the mechanism of cathodic protection of carbon steel is a shift of open circuit potential into the immunity region or reducing anodic reaction rate in active state. The importance of change of pH and soil electrolyte composition during applying cathodic protection is sometime overlooked.
The study deals to influence of cathodic protection on change of pH and anions migration in a soil electrolyte close to protected carbon steel surface. Concentration of chlorides, sulphates and hydrogen carbonates during applying of cathodic protection decreased up to two orders. The migration rate of hydroxide anions during cathodic polarization is lower than their production by cathodic reduction of oxygen. As a result of cathodic reduction of oxygen, the pH of a soil electrolyte close to protected surface gradually increases up to 12.
The final pH of soil electrolyte close to protected surface depends on the migration rate of anions, the diffusion rate of oxygen into soil electrolyte and neutralizing capacity of soil.

In the last decade, magnesium alloys were studied as biodegradable metallic materials due to their unique mechanical properties, such as density, specific strength and modulus of elasticity similar to human bone. But they extremely susceptible to corrosion in physiological environment and this situation hinders their possible implementations in medical applications. This research investigates the effect of Poly(Lactic-co-glycolic) acid (PLGA) and Poly(vinyl alcohol) (PVA) coating on the in-vitro corrosion behaviour of AZ91D magnesium alloy. The coating was achieved by dip coating method in different polymer concentrations and immersion cycles. The coating morphology was examined by scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS). The degradation rate of AZ91D alloy was determined by potentiodynamic polarization tests and weight loss experiments in simulated body fluid (SBF). Results have shown that the biopolymer coated specimens have better degradation resistance than uncoated AZ91D alloys, which could be used in load bearing orthopaedic applications in the very near future.

Water-based coating systems are becoming more popular with consumers due to their simple application and a wide range of colours. The coating systems, in addition to the requirement of nice finishes, are supposed to provide the sufficient protection of background material from corrosion. According to manufacturers, some modern water-based coating systems do not require any pretreating of the underlying material. In this context it is important to understand what influence avoiding underlying material pretreating before subsequent application of coating systems could have in terms of future protection against the effects of corrosive environment. At the boundary of two different environments there can be corrosion products developed, which may cause more hidden corrosion development under certain circumstances. The most frequently ignored corrosion agents include dust.
For protection of the background material the coating system must eliminate those agents effectively. In addition to the aesthetic requirements from consumers, the protection of the background material must also meet environmental aspects. The question is to what extent coating system manufacturers are able to meet these requirements.