Seznam abstraktů 2017: POSTEROVÁ SEKCE D
Datum: 25.5.2017
The processes of chromium-free passivation of zinc coatings have been developed.
It is shown that protective cerium and silicate-containing coatings on galvanized
steel parts are comparable in protective characteristics to opalescent chromate coatings.
It is revealed that the developed coatings withstand sharp temperature differences without
degrading ofcharacteristics. It is shown that cerium-containing coatings have the ability to self-heal.
The paper analyzes the influence of the new flux cored wire intended for cladding process by different sets cladding parameters. Technological parameters of the cladding process such as welding speed, power source setting, the length of projecting portion of the electrode, thermal conductivity coefficient of aluminum and cooper for heating dissipation was analyzed. Description of the influence of this parameters was made as a function of the hardness distribution and structure in bead. The results of hardness distribution analysis allows to illustrate the nature of the impact of the examined input variables on parameters of developed surface. The most important parameters of the deposited hard layers here are the hardness distribution and structure of bead. The cladding processes was conducted by Flux Cored Arc Welding (FCAW). As additional material for cladding material type of Fe-Cr-C-with additional composite was used. To describe the properties of the layers visual test (VT), penetrant testing (PT), Vickers hardness, optical microscope (OM) and scanning electron microscope (SEM) were used. For the describe the level of protect the wear surface the test G65 was conducted.
Mechanically stiff construction components resistant to both abrasion and corrosion need to be made of quality metallic materials. Special alloys with high hardness and corrosion resistance are also quite expensive, simpler and less costly solution lies in use of high-strength metal matrix with hard, abrasion-resistant ceramic or cermet coating. Model example of these systems are pump plungers for liquids with high amount of abrasive microparticles, used in mining industry and ore mining, eventually in industrial waste disposal. Additionally to a high abrasion resistance, corrosion resistance is also required to prevent corrosion under coating.
In this study, special ceramic coatings were prepared on steel (1.0060 – EN 10027-2) by the plasma spraying technique, using plasma generator WSP®-H with output of up to 40 kg/h aluminum oxide. Corundum coatings were deposited directly on the surface of steel plungers equipped with anti-corrosion layer of zinc phosphate. Coating adhesion properties were tested according to pin-off tests (modified ISO 4624) and reached maximum value of 26 MPa. Corrosion resistance was evaluated by measurements of impedance spectra in 100 kHz – 10 mHz range in water solution of sodium sulfate. The capacity of electric double-layer varied depending on the porosity and thickness of the coating. Low-porosity coatings of >1,5 mm thickness had RCT 1.29·105 Ω·m2. Abrasive resistance of coatings was measured by rotary/machining test with SiC cutting knives, using downforce of 50 kg cm-2. Abrasion losses decreased with quality of finish – starting at 0.00266 g cm-2 min-1 down to virtually zero losses after polishing the surface below Ra = 0.55 µm.
The paper presents the results of studies aimed at determination of corrosion resistance intermetallic phase matrix of FeAl alloy in a steam environment at 850 °C. The comparison of heat resistance of Fe40Al5Cr0,2TiB intermetallic alloy with heat-resistant steel with austenitic structure X25CrMnNiN25-9-7 was also presented at the article. After surface corrosion studies, the chemical composition of corrosion products was determined. The obtained results showed very good resistance of Fe40Al5CrTiB alloys to high temperature corrosion in steam environment compared to corrosion resistance of X25CrMnNiN25-9-7 steel. The results of research conducted in this field are the basis for further research.
The article deals with the evaluation of the functional surfaces of the ball valve body, which are different from other parts of the ball valve. First is the requirement of increased roughness of the machined surface of the catch surfaces and areas where it will be used a special sealing element, and also in dimensional tolerances and, ultimately, the position tolerances, such as concentricity, perpendicularity and parallelism.
The demand for coatings that can protect the base material from the influence of high temperature corrosion is nowadays increasing. For this reason, new coatings with potential to succeed in aggressive environments of energy, marine, food, etc. industries are being developed. TiMoCN-29% Ni (experimental coating) and Cr3C2-25% NiCr coatings were applied to the substrate material 1.4923 (P91) which is used as an effective material for structural components in power equipment. Evaluated coatings were deposited using optimized parameters of HP/HVOF (High Pressure / High Velocity Oxygen Fuel) thermal spraying technology. Resistance study of selected thermally sprayed coatings against high temperature corrosion was conducted in the corrosive environment of 60% V2O5 and 40% Na2SO4 at the temperature of 750 °C and in the environment of 59% Na2SO4, 34.5% KCl and 6.5% NaCl at temperatures of 525 °C and 575 °C. After the corrosion tests, the evaluated coatings were analyzed using optical and scanning electron microscopy (SEM) and subsequently the elemental composition (EDX) of each coating was conducted. Based on the results achieved, the experimental TiMoCN-29% Ni coating by the Japanese company Fujimi was further evaluated using X-ray diffraction. The obtained results prove that not all coatings deposited using HP/HVOF thermal spraying technology can be used as an appropriate protection for functional component surfaces.
The paper describes edges deburring processes and polishing of the surface using ceramic tools (brush) based on aluminum oxide fibers. The construction of basic types of tools and their practical industrial applications were described. The effect of machining parameters on surface roughness was evaluated.
This paper is focused on tribological behavior of the plasma nitrided 42CrMo4 steel at elevated temperature to 300 ºC. The hardened steel was treated in plasma in two variants of nitriding atmosphere: 3H2 1N2 and reverse ration 1H2 : 3N2, which is greater nitrogen concentration. This leads to form the nitriding layers with different phases, therefore, to distinct mechanical and tribological of nitride layers. The ball on disc test was performed at variation of loading, ball material and temperature. A profilmeter was used to investigate the wear track on disk surface. Experimental results indicated that the coefficient of friction changed over the test time and temperature, and plasma nitriding in the atmosphere of 1H2:3N2 improved wear resistance better than nitriding in the atmosphere of 3H2:1N2.
One of the most important two-phase alloys α+β is Ti–6Al–4V, which is frequently used in medicine. This alloy is characterized by innovative combination of strength, good corrosion resistance in the environment of chlorides, the highest biotolerance and the lowest Young's modulus. Ti–6Al–4V is the basic material for long-life implants in orthopaedics, traumatic surgery, dentistry or cardiology. Taking into account current level of technology and operating methodologies, the use of metal biomaterials remains to be necessary. However, technological progress causes an increase interest in development of new materials with the possibility of stimulation for osseointegration. The metallic and ceramic sintered are numbered among multi-phase materials and are considered as materials with functional properties, such as increased resistance to fracture toughness and porosity, very good biocompatibility compared to other metallic biomaterials and fatigue strength. Modification of the surfaces of engineering materials especially titanium alloys is intended to improve function and usability these materials (e.g. good corrosion resistance in the environment of human tissues). The sinters for analysis were obtained using the most modern methods of powder sintering
i.e. spark plasma sintering (SPS), powder metallurgy (PM). The main aim of the study was to evaluate the surface morphology of the alloy and functional properties after the thermal oxidation at different temperatures. The results of optical microscope metallography, SEM/EDX, XRD analysis are also presented.
The paper deals with the investigations of application of vibratory tumbling to smooth the surface of gears. The gears which were performed by machining process was machined vibratory tumbling. The paper presents compared measurement of roughness and macro photographers gears before and after vibratory tumbling machining.
The paper deals with the investigations which consisted in conducting the process of hardfacing of steel sheets from X10CrMoNb9-1 steel. There were two different claddings marked to sheets through the TIG method. The material used on the weld overlay was as follows: W CrMo2Si, W CrMO91. After hardfacing of steel sheets, the examined samples have been cut from the sheets, from which the metallographic samples have been produced. In the paper, there were photographs of microstructures of metallographic samples attached, which were taken during the microscopic observations.
The surface layer properties of super-hard materials may be modified by a laser beam treatment and the regular texturization is one of possible approaches. The designed experiment was conducted based on two main controlled factors: the average diameter of cavities and the level of the blackening. The obtained dataset was processed with a response surface model for the coefficient of friction as the outcome. Typical statistical analysis of data with quantitative control factors bases on many theoretical assumptions, with the most important and the most influential one: the normality of random noises distributions. Such assumption is often used but rarely it is analyzed for its weakness and large uncertainty in results. The paper describes a non-parametric approach to the statistical analysis of the uncertainty. It releases us from the direct assumption of particular probability distributions. The bootstrap is formally the method based on random resampling with replacement from the source dataset. It allows to identify the whole distribution shape of raw data and related confidence intervals without additional assumptions about particular distribution. The paper presents the analysis processed for the practical case: original, commercially available rings for front sealing sintered from SiC with a texture modified by a laser beam and tested on tribological tester for changed properties. The paper contains notes on encountered difficulties and possible guidelines for similar analysis.
This research paper deals with an effect of injection mold core/cavity surface and their additional treatment on selected optical properties and surface quality of these tool parts. Used mold cavities were made from tool steels 1.2343 (chromium-molybdenum-vanadium-silicon steel with good hardenability) and 1.2083 (martensitic steel with high chromium content), their surface was polished to the roughness of Ra = 0.08 microns (manufacturer guaranteed mirror finish). For purposes of an experiment, injection mold with interchangeable core/cavities was designed and manufactured. Subsequently, simple shape cavities were manufactured (plates with dimensions of 120x120 mm) and further were provided with a specific coating in order to change surface properties. In total, three types coatings were applied; CrN, AlTiN and hydrogenated a-C:H coatings. All cavities were measured using 3D non-contact roughness tester in different areas in cavity (totally 8 areas per cavity were selected in various distances from polymer inlet). Specifically, surface gloss under different reflection angles with respect to coating or tool steel type was evaluated from optical properties. The results show that the additional surface treatment of injection mold cavity with coatings can reduce the values of roughness parameters, however, affect the level of core/cavity gloss.
In the article, the authors attempted to quantify description of the Al2O3/WS2 oxide layers. The description were carried out using image analysis and stereological methods. Objective and precise analysis of the surface topology aim to characterize the Al2O3/WS2 oxide layers obtained by hard anodizing process on an aluminum alloy in differ temerature and different current density. The addition of WS2 to acid bath reduces the friction coefficient of Al2O3/WS2 - PEEK/BG friction pair. The characteristics of matrix of Al2O3 nanofibers with dispered WS2 phase were performed using scanning electron microscopy and X-ray structural studies. Quantitative description of the surface with set of parameters describing topology of the surface before and after friction test had aimed to analyse the wear process and assess the parameters which effects on it.
The thermal spraying of metallic coating (zinc, 15AlZn, etc.) from wire is suitable technique for surface treatment of large structures. This study was carried out to investigate and evaluate the properties of zinc coatings affected by spraying techniques - heated by electrical arc or flame. The panels with different coatings were exposed at atmospheric and accelerated tests. The article gives the overall evaluation of properties of these coatings.
The Cold Gas Dynamic Spray is an innovative coating deposition technique, presenting several technological advantages over thermal spray technology, due to the fact that it exploits kinetic instead of thermal energy. As the coating deposition is accomplished at the solid state, it has characteristics that are quite unique. In addition, tensile residual stresses, oxidation and undesired chemical reactions can be avoided.
Even though the phase and properties of the as-received powder are preserved during the deposition, the presence of chemical reactions or phase changes cannot be entirely discarded. A very small quantity of chemical reactions or phase transformations could be triggered due to the instantaneous heat generation at moment of impact. The bonding process between coating and substrate is also of a great importance on properties of the final microstructure.
This study has the purpose of studying CS deposition of several elementary powders (Al, Ti, Co, Cr, Ni, Fe) and comparing them with the initial states of the powders in order to identify possible changes. A deep analysis on the microstructure of both materials was performed and several properties of the coating were observed using SEM, EDS, XRD and microhardness tests.
The results indicate that there are noticeable alterations on the microstructure of the different materials due to plastic deformation processes which occur on CS and the bonding process is severely affected on CS samples depending on the chosen particles. The as-sprayed sample composition varies greatly when compared to the original one used for feedstock of pure powders.
The present work is focused on the influence of the hardfacing sequence on the structure and erosion resistance of deposited layers. In the researche one type of the additional material with high content of 3,8%C and 22%Cr was used. The process of hardfacing was made by the flux cored wire arc welding (FCAW) with 2 types of welding sequences. There were implemented string beads and weave bead. The analyzed hardfacing welds showed significant differences in the tested properties. This is due to the nature of the deposition process of the string bead and weave bead. Hardfacing made with string beads had numerous chromium carbide type precipitates of (Fe,Cr)7C3 that is characteristic for the materials deposited on the structure of chromium cast irons. The structure of the hardfacing made with weave bead was characterized by dendritic structure. The differences in the hardness measured in these layers were up to 270 HV. Erosive wear tests were carried out with using corundum and a modified position of the jet milling and with 2 impingement angles.
The service life of components used in the construction, mining or agricultural industry depends on several factors. Primarily is influenced by the type of wear to which the parts would be subjected (for example abrasion) and environment in which components perform their function. The choice of material and technology depends on these factors. The part exposed to abrasion can be made entirely from a durable material, which is often quite expensive. Another possible approach is the production of part from conventional structural steels, such as steel S235JR. Consequently, worn surface can be equipped with a layer of highly wear resistant material (e.g. by weld deposit) which prolongs the service life of entire component and reduces costs for producers and customers to its repair or replacement.
This study deals with the evaluation of wear resistance test of selected weld deposits combining FeBNiCr matrix with an increased content of the boron and tungsten carbide particles spread in monolayer weld deposit and all at once with comparing microhardness in selected areas of the welded layer. This weld deposit was made on S235JR structural steel using hard-facing with cored wire in protective atmosphere of argon and carbon dioxide mixture. Further this contribution deals with evaluation of abrasion mechanisms appeared on the surface of the weld deposits in selected areas.
Here is a significant trend of bioactive coated implants in field of medicine during last few decades. This coatings can be divided into two main groups-organic and inorganic coatings. Hydroxyapatite (HA) is well known as one of inorganic part of mammal’s bone structure and is highly recommended for use in implantology. This paper is mainly focused on characterization of hydroxyapatite particles electrochemically deposited from water solution of Ca(NO3)2 and NH4H2PO4 on surface of AISI 316L (1.4404) stainless steel with different roughness profiles and surface treatment. The effect of surface roughness itself is discussed as well as heat treatment (400°C) of samples after coating deposition. Electrodeposition of HAP was carried out at constant potential values of −2.0 V for different time periods. Electrochemical properties of such treated samples were characterized using voltammetry and EIS methods. It was found, that time of deposition significantly changes electrochemical parameters of equivalent el. circuit used for closer characterization of coating properties but only marginally affects corrosion properties like open circuit potential (OCP), corrosion potential (Ecorr) or potential of passive layer breakdown (Ebreak). It was also found that time of deposition increases polarization resistance. Pull-off test also proved significant correlation between surface roughness, heat treatment and adhesion of deposited coatings.
This paper deals with a method enabling the preparation of thick metallic microstructures on metal substrates. Such metallic microstructures can be used as a resolution samples to characterize various microanalysis techniques, such as X-ray fluorescence (XRF) or X-ray photoelectron spectroscopy (XPS). Moreover, the patterned samples could be used as anodes to characterize focusing properties of X-ray tubes for micro CT systems. Considering that the standard lift-off technique is designated for structures with the thickness of several hundred nanometers at most, we had to modify lift-off technique to be possible to use it for preparation of very thick metal layers (several microns) with spatial resolution of a few microns. The mask with the desired pattern for UV exposure was prepared by e-beam lithography. SU-8 photoresist was used for a lift-off because of its aspect ratio ability, process purity and high resistance to heating. We used a thin layer of PMMA under the SU-8 masking layer to guarantee the photoresist would lift-off correctly. Thick aluminum layer was deposited by thermal evaporation. The dependence of metal layer thickness as a function of required exposed line width was determined. The final lift-off process was carried out in acetone ultrasonic bath. Generally, this technology can be used for the evaporate deposition of various materials with several microns thick layer in micron resolution.
Composite (Ni)+Ni3Si coatings on C45 steel-substrate could be easily developed via three-step technology: electrodeposition of nickel interlayer, sediment co-deposition of Ni+Si and subsequent vacuum annealing at 980 C for 5 h. The results of hardness measurements showed that as-plated Ni+Si coating was 1.7 times harder than the electrodeposited Ni coating, but the hardest was (Ni)+Ni3Si coating (820HV) due to the presence of the super hard Ni3Si phase. At 1000 C, (Ni)+Ni3Si coatings followed parabolic oxidation kinetic. During oxidation a thin continuous SiO2 layer formed below a layer of NiSiO3. After 100 h at 1000 C a mass gain for (Ni)+Ni3Si coating was about 6 times lesser than for nickel coating. The wear mass loss of the (Ni)+Ni3Si coatings was approximately 2.5 times smaller than for as-plated Ni and Ni+Si coatings. The oxidised for 50 h (Ni)+Ni3Si coatings containing hard and wear-resistant SiO2 particles also showed smaller wear mass loss than Ni and Ni+Si coatings.
Titanium dioxide (TiO2) is one of the most useful materials in various applications related to catalysis, electronics, photonics, sensing, and medicine. TiO2 is characterized by high chemical stability, outstanding optical and electrical properties, a non-toxic nature, and ease of mass production, and this is what causes it to be successfully used as a photocatalyst in many fields such as anti-bacterial applications, water purification, the decomposition of various organic pollutants, and solar cell applications TiO2 thin films can be prepared by a variety of methods, such as the sol–gel method, pulsed laser deposition, chemical vapour deposition, spray pyrolysis, and sputtering techniques. The magnetron sputtering method can produce highly homogeneous films characterized by good adhesion to the substrate. This method also offers the advantage of depositing films on a large scale area, which makes it suitable for industrial applications. TiO2 coatings prepared by magnetron sputtering method have two types of crystallographic structures: rutile and anatase, which are characterized by difference properties. For example, anatase can be characterized by better photocatalytic properties, while rutile has a higher absorbance property than anatase. Depending on the contribution of particular phases in the crystalline structure, the TiO2 coating is characterized by different functional properties. The article presents the influence of the chemical composition of the process atmosphere on phase composition TiO2 coatings obtained by reactive magnetron sputtering. The research methods also include the microstructure and the mechanical properties analysis of the obtained coating.
The coated materials are of a great importance for many engineering components since they improve the structural integrity in various aspects. With respect to their function, the coatings can protect material surface or ensure surface hardening. The later type of coatings are carburized or nitrided surface layers. They increase the surface hardness of a substrate and introduce compressive residual stresses. This results in a higher resistance to fatigue and wear of low-carbon steels that are mostly used in various dynamically loaded components as gears and shafts at room temperature. The paper is focused on a determination of the residual stresses in a nitrided layer using a recently proposed original method applicable for surface hardened coatings. This method is based on a measurement of true stresses in the centres of fish-eye cracks initiating the fatigue fracture in samples loaded by cyclic bending and a comparison of the related S-N curves for samples with and without coatings.
Thanks to its unique properties such as high melting point and density, tungsten and tungsten-based alloys are commonly used in wide range of applications. Among others, these materials are promising candidates for the plasma facing components in the future fusion reactors. One of considered ways of production of these parts is plasma spraying. There are however several limitations for conventional gas stabilized torches, mainly in plasma enthalpy (therefore the ability to efficiently melt tungsten particles in considerable feed rates) and susceptibility of tungsten to oxidation (which complicates spraying in oxidizing atmosphere). The radio frequency inductively coupled plasma torch (RF-ICP) is a unique system which can potentially overcome both these problems and can be effectively used for tungsten spraying. The powder, which can be finer than the one used for conventional systems, is fed axially into the hot plasma core; both factors lead to more efficient melting of the particles. The deposition is performed in a chamber with controlled atmosphere of inert gas or decreased pressure, the oxidation is therefore suppressed. In this first study carried out with newly commissioned RF-ICP system TekSpray 15 (Tekna), samples of tungsten coatings on graphite substrates were prepared. The X-ray diffraction and SEM pictures of the free surfaces and cross-sections were obtained, documenting high purity of the deposits and appropriate flattening of the splats leading to dense microstructure. The effect of substrate preheating on the microstructure, porosity and hardness was studied.
The work presents the influence of laser cladding parameters on microstructure, chemical composition and mechanical properties of Inconel 686 coatings. To obtain coating with the best quality the different parameters of laser cladding were used. The substrates were boilers plate 13Mo4-5 steel. Ni - base alloys characterized by excellent high temperature corrosion resistance, good strength and good ability to work in aggressive environments were used as the coatings. Applied coating should have a good combination of the metal substrate and small amount of Fe. Too high amount of Fe in the coatings leads to decrease resistance to high temperature corrosion. The narrow heat-affected zone limited the diffusion of Fe to coatings. The microstructure (SEM,TEM), mechanical properties, chemical composition (EDS) and Fe distribution in coatings were investigated and presented in the paper.
Cold Gas Dynamic Spraying (CGDS) method was used in order to obtain very dense and good adhesive CoNiCrAlY-coatings deposited onto nickel-based alloy and subsequently remelted by electron beam (EB) up to depth of about 90 m. The CGDS process- a relatively new coating technology is based on the high velocity impingement of small solid particles on the substrate. In this process, the particles are accelerated by supersonic gas jet at the heated gas temperature, which is usually lower than the melting point of the powder material. The objective of this work is to investigate the influence of the parameters used in electron beam remelting even the effect of double EB remelting on the microstructural changes and state of the coating. Changes of the coatings morphology and structure were analysed by scanning electron microscopy (SEM) and X-ray diffraction technique (XRD). The experimental results demonstrated that there are advantages at using the pulsed EB surface modification technique. The double remelting proces improved the coating properties in terms of porosity, strength and chemical homogeneity.
Increasing demands for reducing the surface roughness of components impose high requirements for finishing operations. As a result, it creates a space for the application of new progressive methods for the surface finishing of components. The experimental activity referred to in this paper aims at comparing the conventional method of surface finishing (surface grinding followed by polishing) and a progressive finishing operation – forming with a diamond tip. The experiment was designed for the Wotan RJN 44 grinder and the Wagner WDR 1000 lathe. As the material to be machined, 17150 according to CSN was chosen. Forming with a diamond tip was made using a tool from Baublies, DDW type. The aim of this experiment was to compare the two finishing operations with the criterion for evaluating surface roughness Ra = 0.2 µm.
The goal of this paper is to analyze mechanical properties of steel long weld structures. The main role of welding conditions in connected with materials, alloy elements in steel and filer materials, welding technology, state of stress and temperature. First time are presented properties of steel long weld structures after welding with micro-jet cooling. Because of that very important is good selection of steel and welding parameters for proper steel structure. In this study metallographic structure and impact toughness welded joints has been analyzed in terms of welding parameters after laser and MIG welding.
One of the greatest problems of modern production techniques is the achievement of an appropriate quality at minimal costs and accompanied by the production efficiency increase. Therefore while designing the production process, the technology used should have a considerable influence on the durability and reliability of machine parts to be produced. During finish treatment the final dimensions as well as functional properties are imparted to a given element by application of proper treatment type. The engineer has a range of production techniques to choose for the proper surface layer formation. It is crucial to find a suitable solution which will meet the requirements as well as the work conditions of a given machine part.
The article presents the research results referring to the analysis of the influence of cutting parameters on surface roughness parameters of marine pump shaft. The turning process was carried out on a universal CDS 6250 BX-1000 centre lathe. The research were performed on a shaft made of X5CrNi18-10 (AISI 304L) stainless steel. The finishing turning process was carried out by cutting tool with CCET09T302R-MF replaceable insert by DIJET. During turning the following machining parameters were used: cutting speed Vc = 226 m/min, feed f = 0.044; 0.062; 0.083; 0.106 mm/rev and cutting depth ap = 0.25; 0.5; 0.75; 1.0 mm. The goal of the paper was to define the influence of treatment conditions on surface roughness parameter. The surface roughness parameters was measured by T8000 profilometer.
In the present study, the method of non-vacuum electron beam cladding of powder mixtures containing 10, 20 and 30 wt. % of boron carbide, titanium and welding fluxes (CaF2, LiF) was used for synthesis of titanium carbide and titanium boride particles. The structure, phase composition, microhardness and tribotechnical properties of the samples of commercially pure titanium after surfacing were investigated. The thickness of the obtained coatings was 1.4 ... 1.7 mm. The main phases of the cladded layers are alpha-titanium, titanium carbide with a cubic lattice of TiC (B1), titanium monoboride with an orthorhombic lattice TiB (B27). The obtained data were confirmed by microstructural analysis data. The microstructure of the coatings consists of hardening titanium carbide and titanium boride particles distributed in the titanium matrix. All coatings contained 0.2-0.89 vol. % of undissolved boron carbide particles. The factor, which determines microhardness and tribotechnical properties of the obtained materials, is the hardening particles containing in the coatings. The average microhardness value of the coatings was 395, 521 and 565 HV at 10, 20 and 30 wt. % B4C, respectively. The tribotechnical tests at the conditions with fixed abrasive particles exhibited the 3 times higher relative wear resistance of the coating formed by the 30 wt. % B4C compared to commercially pure titanium.
Electrochemical chloride extraction from a reinforced concrete structure may be accompanied with an electrochemical injection of healing agents if such agents are positively charged and are able migrate towards the activated reinforcement. Positive charge carrying nanoparticles or cathionic corrosion inhibitors might be the proper choice. Organic substances with a positive charge and their salts are mostly such inhibitors. The essential conditions for successful application of such corrosion inhibitors are their sufficient corrosion inhibition efficiency that was studied and evaluated elsewhere and their stability of positive charge in alkaline concrete environment and their migration ability through concrete pore system.
Considering the cathionic corrosion inhibitors, several commercially available compounds were tested. Active components in commercial mixtures were dimethyl-didecyl ammonium (bi)carbonate, polyethylenimine and imidazoline, guanidine carbonate, methylamine, tetrabutylammonium bromide or tetrabutylphosphonium bromide. Their cathionic stability as a function of pH of the model concrete pore solution was studied by means of zeta potential. The results show that only guanidine carbonate is prospective corrosion inhibitor at realistic concrete pH level in terms of positive charge stability.
Migration ability of cathionic corrosion inhibitors was tested using a migration cell with controlled potential of the cathode behind an OPC concrete membrane or with constant current flowing through the system. The inhibitor concentration profile was scanned by means of EDS after the electrochemical injection process. All the tested corrosion inhibitors show very low permeability, thus very low migration ability.
Acknowledgements: Financial support of the Czech Science Foundation (project 16-11879S) is gratefully acknowledged.
The article presents the impact of cutting inserts with coatings on the roughness of the milled surface. Two types of coated steel inserts were selected for the research purpose. The first one was covered with Ti (C, N) + Al2O3 coating, while the other was TiC / TiN-CVD and Ti (C, N) + Al2O3. They were then mounted in a milling head. The process of surface milling has been subjected to C45 steel. Milling process for each inserts proceeded at the same rate of cutting. After a certain number of tool passages, the measurements of wear parameters and the roughness of the milled surface were measured. This allowed us to determine the effect of tool wear on the properties of the milling face layer.
Tungsten carbide (WC) is in the groups hard materials, which is used for cutting tool. The substrate sample was coated with device PVD. Coatings nc-WC/a-C:H were deposited in a vacuum chamber by magnetron sputtering. This device has four independent planar magnetrons with circular targets. Three targets were made from pure graphite and one form pure tungsten. Tungsten carbide is approximately two times stiffer than steel, with a Young's modulus of approximately 650–700 GPa. At the end of the coating process Ar/methane (Ar 25 sccm / CH4 12,5 sccm) was admitted to chamber, which gets into the surface layer The parameters of the process influence properties of the thin films were amourphous microstructure, hardness and adhesion to the substrate. The tribological measurements were performed the “ball-on-disc” testing method. Tribological testing (EN1071-13:2010) was performed using a ball made from Si3N4 with a diameter of 5 mm, with a constant load of 10 N at room temperature and humidity of 40±2 %. The Results were analysed by profilometer and optical microscope.
The surface properties of hydroxyapatite (HA) deposited on the Ti-6Al-4V substrates by plasma spray technologies were studied. Two different plasma spray technologies (hybrid plasma spray system (WSP) and atmospheric plasma spray technology (APS)) and two various feedstock (suspension of hydroxyapatite for HPS and hydroxyapatite powders for APS) for deposition of HA layers suitable for bioaplications were used. The layers properties (thickness, porosity, chemical and phase composition) and coating-substrate interface quality were analyzed.
The XRD analysis showed that there were formation small amount of new phases (TTCP and CaO). Better coating-substrate interface quality on samples prepared by WSP was observed. The results showed that WSP system is more suitable technology for deposition hydroxyapatite than APS.
The paper presents the properties of diamond-like carbon (DLC) coatings deposited by PVD technique. Their properties were determined by structure observation, hardness tests, texture analysis and tribological tests. The hardness of coated and uncoated elements was measured using a Matsuzawa microhardness tester. The coating structure was analyzed by observing the topography of the surface and the cross-sections using a scanning electron microscope SEM type JSM 7100F, equipped with the EDS X-ray microanalysis. The results were employed to determine the elemental composition, phase distribution and thickness of the coatings. Analysis of the chemical composition of the elements present in the samples was performed. The topography maps of specimens surface measured the optical profilometer Talysurf CCI Lite optical profilometer. The wear resistance was established under dry friction conditions using a ball-on-disc tribometer, with the ball being made of 100Cr6 steel or 100Cr6 steel coated with DLC and the disc being made of the 100Cr6 steel coated with DLC. The experimental data indicate that DLC coatings improve the service life of elements. The results of the structure analysis and the tribological tests performed diamond-like carbon (DLC) coatings were compared with those obtained for the substrate material, i.e. steel. The study aimed at assessing how the coating and the material used for counter samples, i.e. a steel ball and a DLC ball affects the tribological properties of the elements operating under dry conditions. Compared with the substrate material (steel), the diamond-like carbon coatings showed lower linear wear, lower friction coefficient and higher hardness.
In this study, suspension plasma spraying of slightly sub-stoichiometric titania (TiOx) was attempted using hybrid water/argon stabilized plasma torch (WSP-H). Porous coatings with fine cauliflower-like columnar microstructure were successfully deposited in two separate experiments with different power levels of the plasma torch. In both cases, high solid-load content (40 wt.%) of the water-based suspension resulted in considerable coating thickness increase per deposition cycle. Coating annealing and partial remelting of the surface asperities were also achieved by additional pass of plasma torch in front of the coating surface. According to X-ray diffraction, all coatings consisted dominantly of rutile phase. Detailed microscopic observation of the as-sprayed and annealed deposits showed that the local coloration of the coating (ranging from dark grey to beige) was driven by the local overheating of the rough coating surface which could also promote the oxygen intake. Moreover, sample annealing was also observed to increase the sample reflectivity as observed by UV-VIS-NIR scanning spectrophotometry.
Blast-cleaning is one of the often-used technologies of surface pre-treatment. Its main use is in the area of anticorrosive protection of materials, as the last technological operation prior to the creation of protective coating. The basic principle of abrasive blast-cleaning is the hurling with high kinetic energy of abrasive blast-cleaning material against the surface of a material. The results are the cleaning of the surface of a material from drosses, rust and other impurities, the creation of a characteristic microgeometry of the surface and also the significant effect on the surface layer of a material. All these parameters have a significant impact on the resulting adhesiveness of protective coating of a material to the base material. The following paper presents a complex analysis and evaluation of the surface of a material after abrasive blast-cleaning. A cylindrical intermediate product was blasted with three different types of media. The analysis of individual surfaces included, for instance: the assessment of purity of a surface according to ČSN EN ISO 8501-1, measurement of surface stress in the base material using test inks, a metallographic analysis, assessment of surface asperity, assessment of microhardness and the analysis of residual stress using the magnetoelastic method. On the basis of these analyses, it is possible to clearly set the optimal parameters of surface abrasive blast-cleaning prior to the creation of protective coating.
Wire electrical discharge machining (WEDM) belongs to the advanced technology widely used in the engineering industry. In WEDM process material is removed from workpiece by series of electrical sparks. The article studies the interactions between process parameters and the final quality of the generated surface (for steel 1.2201). The influence of WEDM parameters: initial current Iw [A], initial pulse time tw [µs], discharge duration ton [µs], on the surface roughness were experimentally evaluated. The obtained results show that surface roughness Ra after WEDM process for the first cut is the range between 1,9 – 2,5 µm. The primary factor in determining the treatment process is the energy of electrical discharge. The effect of the WEDM parameters on the functional parameters of surface roughness: Sk - roughness of the core, Spk roughness of the peak, Svk - roughness of the valleys are also presented and discussed.
We propose a new effective method to reduce the diffusion of catalyst material inside of bulk stainless steel 304 (SS304) to grow carbon nanotubes (CNTs). A SS304 substrate foil of 0.1 mm thickness was cleaned using Ar plasma to etch the native oxide film. The diffusion barrier was deposited as follow. Firstly, a gradient layer of nitrided steel was deposited on bulk SS304 substrate by DC-pulsed sputter process using a SS304 target. The sputter process started with 20 sccm Ar flowing during 600 s. Progressively, during 100 s was introduced N2 and reduced Ar until reach 5/15 sccm N2/Ar flowing. This regime was kept during 500 s. Again during 100 s was changed the N2/Ar flowing until 7/13 sccm and it was kept during 500 s. The deposition process was carried out at 1 Pa of total pressure and at room temperature. Secondly, a 10 nm thick aluminum nitride (AlN) layer was deposited on top of the nitrided steel gradient layer using DC pulsed sputtering with an Al target with 20/30 sccm N2/Ar flowing and 3 Pa of total pressure at room temperature. The gradient zone acts like a buffer layer between bulk SS304 and AlN layer in order to avoid the formation of cracks in the surface during annealing and during the growing time of CNTs at high temperatures. We used different temperatures to obtain CNTs: 680, 700, 715 and 730 °C. Scanning electron microscope (SEM) images show the influence of temperature over the performance of this new configuration.
The paper describes a non-parametric approach to the statistical analysis performed on data obtained during investigation on the airfoil blade traces. This approach releases us from limits of many conditions. Typical statistical analysis of data, with factorial (qualitative) control approach, bases on many theoretical assumptions, with the most important and the most influential one: the normality of random noises distributions (usually named ‘errors’). The solution is the bootstrap approach, originally proposed by Efron in 1979, later in 1995 described in details by Shao and Tu. The bootstrap is formally the method based on random resampling with replacement from the source dataset. It allows to identify the whole distribution shape of raw data and related confidence intervals without additional assumptions about particular distribution. The paper presents the practical case: the factorial approach performed for the fixed-effect analysis of the relation between secondary dendrite arm spacing and carbides for the airfoil blade traces. The paper contains notes on encountered difficulties and possible guidelines for similar analysis.
Plasma nitriding is a thermochemical treatment, widely used in many technical applications as a final operation to improve the mechanical, tribological and corrosion properties of steel. This paper is focused on plasma nitriding treatment of X12Cr13 martensitic stainless steel. For nitriding of martensitic stainless steel was two stage plasma nitriding proces performed. The nitrided X12Cr13 stainless steel was characterized by measuring depth profiles and residual stress. Measuring of residual stress was carried out by X-ray difraction on the Stresstech Xstress 3000 G2R device. To identify critical areas in terms of surface integrity was used Barhausen noise analysis. The verification of material chemical composition was carried out by OES Oxford FOUNDRY-MASTER device. The objective was to verify the nature of the residual stress before and after thermochemical treatment. The depths of the plasma nitride layers were estimated using cross-sectional microhardness profiles measuring. Microhardness and surface hardness of plasma nitrided steel samples were significantly increased. The samples proir and post thermochemical treatment showed significant differences of residual stress which may be caused by machining with blunt tool, what has a significant influence on the creation of plasma nitride layer as well.
Early steel bars corrosion in reinforced concrete elements is difficult to detect because of the lack of visible changes on the concrete surface. To assess reinforcement corrosion risk level without structure damage some non-destructive diagnostic methods are applied. One of them is the galvanostatic pulse method. This semi-non-destructive electrochemical method allows to determine the corrosion areas and estimate the steel bars corrosion activity. Using this method it is possible to measure some electrical parameters (corrosion current density, stationary potential and reinforcement concrete cover resistivity) that allow to indirectly estimate the reinforcement corrosion progress in concrete. So far this method has been generally applied to bridges. The article presents results of studies in which the galvanostatic pulse method was used to determine reinforcement corrosion risk in structures elements different than bridges. Two types of reinforced concrete columns were tested under different environment conditions and two groups of laboratory specimens which were subjected to freezing and thawing cycles in NaCl solution or stayed in natural air–dry conditions. The apparatus GP-5000 GalvaPulseTM was used. Based on the obtained results the conclusions were drawn. The galvanostatic pulse method allows to assess the progress of the reinforcement corrosion process in tested elements. However, it is necessary to measure simultaneously all parameters and make their complex analysis.
The paper described properties of electro-spark deposited coatings. The processes of coating formation on metal parts including electro-spark deposition involve mass and energy transport accompanied by chemical, electrochemical and electrothermal reactions. The tests were conducted to analyze the operational properties of steel beaters used in a hammer mill for waste paper recycling. The degree of wear and the development of wear processes were studied for specimens with and without electro-spark deposited coatings. The studies were conducted using WC-Co-Al2O3 electrodes produced by sintering powders. The anti-wear coatings were electro-spark deposited over C45 carbon steel by means of an EIL-8A.The operational properties of the specimens were assessed by analyzing their micostructure, microhardness, surface geometric structure, corrosion resistance and tribological properties. The results show that more effective methods are required to increase the durability of beaters for hammer mills.
The engineering ceramics are commonly used as a coating materials in machining steel and non-ferrous alloys industry, mainly to increase the durability tools working in different operating conditions. Coatings based on borides, nitrides or carbides have high hardness and good tribological properties at room and at elevated temperatures. TiB2 is a unique material characterized by to the low affinity to aluminum and its alloys what causes it to be successfully used to production thin anti-wear films dedicated to increase the durability of the tools used non-ferrous metal processing industry. This compound is also considered to be superhard materials (hardness up to 30 GPa). Titanium diboride hardness, depending on process parameters and using production method, is in the range of 30-40 GPa. Unfortunately, this material has high brittleness, what create the limits of the area application.
The paper presents influence of negative substrate polarization on mechanical properties (HV, E) and fracture toughness (KIc) of TiB2 coatings. All coatings obtained using magnetron sputtering method on samples of SW7M steel heat treated to hardness 59 HRC. The result of increase of negative substrate polarization is increase hardness and Young Modulus. The fracture toughness obtained coatings remained at a constant level of 0.6 MPa*m1/2. This means that the coatings are very brittle. In the case of polarization Ubias = -75V, the authors achieved 3 times higher brittleness index KIc and increase of hardness to 36 GPa simultaneous.
The Article is focused on determining the influence of the geometry of the cutting inserts on the surface of the micro-geometry of the plasma thermal spraying after machining. Thermal plasma spraying is especially important in terms of increasing the useful properties of machine parts, but also for their renovation. The process machining thermal plasma spray requires a specific approach, in which must be met all the requirements on the surface quality of the norm for aviation. As a test sample was selected for machining coated with the designation Metco 52C-NS. This is an abradable coating that acts as a mechanical seal blades of jet air compressors. For machining surface Metco 52C-NS were chosen cutting inserts RCMT and DCGT with different size and tip radius rɛ. In connection with the geometry used cutting inserts were designed cutting machining conditions so as to meet all the requirements for the quality of machined surface thermal spraying and also achieve savings in machining time.
Electrical discharge machining (EDM) is precision method of manufacturing complex shape conductive materials, which is widely used in aerospace, automotive and mold making industries. In EDM material is removing with the series discharges occurring in the gap between two electrodes. Resulting of thermal removal process are specific properties of surface roughness, metallurgical transformations and micracking. This paper is considered on influence of electrical discharge energy on surface integrity. Properties of surface texture and microstructure of tool steel 1.2713 after EDM was described. The experiments were conducted using copper electrode while varying discharge current, pulse duration and pulse interval. Observations of metallographic structure show that discharge energy have a strong influence on thickness of recast layer and heat effect zone. The effect of the parameters of EDM process on surface integrity was described and discussed.
316L stainless steel is widely used in orthopedic implants in human body because of its corrosion resistance, mechanical properties and biocompatibility. When 316L stainless steel is coated with hydroxyapatite layer, which has a chemical composition similar to bone tissue, the interfacial adhesion between implant and bone tissue can be improved. For this purpose, electrophoretic deposition technique (EPD) can be preferred in implant coating applications, because of its advantages like short formation time, simple apparatus needs and little restriction of the shape of substrate. In this study nano-sized hydroxyapatite powders were coated on 316L stainless steel substrate by electrophoretic deposition. Isopropyl alcohol containing 1 wt-% nano hydroxyapatite powders was prepared as the dispersion and sodium dodecyl sulfate was used as surfactant. The deposition was performed at 10, 20 and 30 V for 5, 10 and 15 minutes duration. The effect of applied voltage and the deposition time on the deposition process was studied. After heat treatment, microstructural characterization of the coatings was carried out using SEM and XRD examinations.
This study experimentally evaluates the effects of chemical composition, particularly the amount of silicon on the quality of the applied coating technology of hot dip galvanizing. The experiment is aimed at determining the microstructure, thickness and quality of the zinc layer on the test samples of different steel grades. For the experiment, structural S235JR and S355J2 steels with low silicon content were selected. High strength steel S690QL with higher silicon content was chosen for comparison.
Results of independent measurements of coating thickness using optical microscopy and magnetic method indicate only minimal differences between steel S235JR and S355J2. Steel S690QL exhibits thick and uneven layer of the zinc. Steel S690QL should be evaluated as unsatisfactory type of steel for hot-dip galvanizing.
The results of corrosion resistance of aluminum alloy 5754 used as construction material in the automotive industry has been presented in the paper. The samples of aluminum alloy were treated with an acidic salt mist atmosphere containing copper chloride as a corrosion initiator according to ISO 9227: 2012 and linear and cyclic potentiometric methods according to PN-EN ISO 10271: 2012 and impedance spectrometry according to PN-EN ISO 16773: 2009. In order to correlate the test as a corrosive environment, an acid brine solution was used at 50 ° C. The results obtained have been developed in terms of corrosion, its extent and type in acidic corrosive environment. It has been found that the material tested is relatively resistant to corrosion in a strongly corrosive environment, which justifies its use as a structural component in the automotive industry.