Seznam abstraktů 2019: SEKCE D - MODERNÍ TRENDY V POVRCHOVÉM INŽENÝRSTVÍ
Datum: 22.5.2019
The present work investigates the influence of surface finish and heat treatment, commonly used in alloy wheel manufacture, on the microstructural modification and corrosion of cast (A356) aluminium alloy. Different depths of near-surface deformed layer are present depending on the surface finish, with a finer finish producing a thinner deformed layer. Coarsening of the ultrafine equiaxed grains, typical of a near-surface deformed layer, are observed after heat treatment. Significant changes to the electrochemical behaviour of the alloy can occur as a function of surface finishing and this can have adverse influence on the corrosion performance of manufactured components.
The purpose of the work was to assess the influence of the vibro-abrasive treatment on the quality of the zinc coating. The use of vibro-abrasive finishing in the production process of fittings for overhead power line is designed to improve the aesthetics of the coating by eliminating zinc beads and burrs, as well as shorten the time of detecting the details on the production. Research was focused on ball-eye links, made of steel grade 41Cr4. The vibro-abrasive machining was carried out in an R 320 device using porcelain polishing fittings type R 8/10 and technological liquid type COMPUND FC after hot dip galvanizing. Comparative tests were conducted for samples without and with vibro-abrasive machining. The effects were evaluated on the basis of metallographic analysis, evaluation of surface roughness and topography, microhardness measurement and corrosion tests. It was found that the use of additional treatment after galvanizing improves aesthetic features of products and does not significantly reduce its corrosion resistance.
The paper presents the results of the study how the sub-zero treatment of Vanadis 6 steel influences the corrosion resistance of the material. The sub-zero treatment was performed at -196 oC in liquid nitrogen for 17 h. The results obtained by sub-zero treatment were compared with those achieved by conventional heat treatment. The main object of the analysis was the effect of these treatments on the corrosion resistance of the steel tested. Corrosion resistance tests revealed slight improvement in corrosion resistance by the application of sub-zero treatment. Tempering treatment, on the other hand, induced a worsening of corrosion behaviour of the material.
The main factor for operating characteristics of sliding bearing is a quality of the lining surface. For low friction and better functionality, the coating of sliding surface is commonly used. The material of coating is usually alloys based on tin or copper. The main methods of coating application of these materials are centrifugal and static casting. The adhesion of such lining is based on the diffusion of tin into steel substrate. In production, the usage of casting technology is limited by proportions and weight of bearings. As alternative technologies of bearing lining deposition, the technologies of thermal spraying and laser cladding can be suggested. In the paper, the first phase of this study is described. The coating was applied by flame spraying, arc spraying and by laser cladding. The materials are tin composition, called also Babbitt, and aluminum bronze. The effect of spray parameters was investigated and the optimal parameters for the spraying were searched. Basic characteristics of the coating, such a microstructure, hardness, surface roughness and adhesion, were tested. Real applicability of coating has also been evaluated. All these technologies were found suitable for deposition of bearing linings with satisfactory microstructural and mechanical characteristics. Such coating could be suitable for hard-working bearing where long-life is required.
Welding and additive manufacturing of titanium and other sensitive materials are particularly problematic due to their high oxygen affinity. The melting pool has to be protected from oxidation not only during the welding proces but also after its crystallization up to about 300 Celsius degrees. In order to protect titanium-melting pool during and after the welding, pure inert gases such as argon or helium with purity 99.999 % should be used. The present study describes the procedure and basic principles for additive manufacturing of Ti. In order to improve the protection of the melting pool, the small chamber with low overpressure was developed in house and it was used to reduce the oxygen content in the welding area due to argon filling. Based on preliminary tests, some basic parts of titanium gr. 1. were welded by PTA method on plasma hardfacing automate PPC25 R6.Text of abstract should have extent to 250 words.
The electrochemical anodization of titanium has received a lot of attention in recent years, especially for its application for biomedical purposes, offering a biocompatible titanium oxide with architecture of a large energy surface, and highly controllable nanoscale characteristics.
In this work, TiO2 layers were synthesized on a well-polished titanium surface, by the anodizing technique, under a voltage of 20 V, for 15, 30 and 45 minutes respectively, using as specific electrolyte: 1M CH3COOH /1M Na2SO4/0.5 Wt% NaF. Interfacial integrity and variation of elemental composition along the interface were studied by scanning electron microscopy (SEM), equipped with an energy dispersive X-ray analyzer (EDX). Electrochemical behaviour was studied both by measuring the evolution of open circuit potential (OCP), by electrochemical impedance spectroscopy (EIS), and by linear polarization (LP) in Hank's solution as a physiological environment. The nature of the crystalline phase formed during the annealing treatment was demonstrated by Raman spectroscopy and X-ray diffraction (XRD) technique. SEM characterization reveals uniform and vertically aligned networks of TiO2 nanotubes (TiO2-NT) on titanium substrates, without a significant effect of anodization time on the diameter of the nanotubes. On the other hand, the EIS measurements show a significant improvement in corrosion behaviour.
Pulse thermography is a method for an inspection of near surface defects. The method is based on heating a tested object with an excitation source (e.g. flash lamp, halogen lamp, laser, microwave) by one pulse. A temperature response is than recorded by a thermographic camera. A result of an evaluation are indications of the defects. The indications are however usually not significant enough or not visible at all without an application of a special data processing methods. A complexity of the evaluation thus often limits a usability of the pulse thermography in industrial applications. The results are often in a form of a sequence composed from many images (typically more than 1000), which should be inspected manually by an operator. We propose and describe a technique, which allows to compress the results to a one image only. This makes an evaluation very fast and very usable for an industrial use. This technique is also suitable for an estimation of depths of the inspected defects. Principles of the proposed evaluation method are described and evaluation results of a steel sample inspection are demonstrated in this contribution. Advantages and disadvantages of the technique are discussed.
The paper offers an analysis of the fluoride conversion coating prepared on ZE10 magnesium alloy with the aim to improve material corrosion properties with respect to the biocompatibility of the alloy. The coating was prepared via unconventional process, by immersion of the alloy in Na[BF4] molten salt at 430 and 450 °C for various treatment times. The coating was analysed in terms of scanning electron microscopy, energy dispersive X-ray spectroscopy and electrochemical impedance spectroscopy. The coating was shown to be compact and homogenous with intermetallic particles incorporated in the coating. Significantly higher values of the polarization resistance were estimated for the coated specimens when compared to the untreated ZE10 alloy in simulated body fluid solution at 37 ± 2 °C.
The study of the geometric characteristics of the metal sheet surface with textured polymer coatings is justified by their connection with mechanical and optical properties. Studying of the surface of coated samples using optical microscopy revealed that it consists of grooves that are assembled into star-shaped clusters scattered across the entire surface of the sheet. At first glance, it seems that these defects are arranged randomly. However, resultats of the production tests showed that the type of defects depends on conditions of formation of the polymer coating. A Method for the constructing a geometrical feature of the surface relief of the polymer coating is proposed. The surface in our model is represented as an array of the clusters of interconnected fractal objects. The surface formation is simulated of completed by the method of random walks.
In the paper, the influence of high temperature and hot pressure steam on the microstructure and phase composition of HVOF sprayed wear resistant Cr3C2-NiCr coating and flame sprayed NiCrAl-Bentonite abradable coating is studied. Both the results of laboratory oxidation tests and the long-term exposition tests in the steam turbine are presented. The mechanism of selective carbide oxidation was observed in both laboratory test and long-term oxidation test in the case of HVOF Cr3C2-NiCr coating. The oxidation of NiCrAl matrix of flame spray abradable coating is described. Both coatings suffered from oxidation, but their integrality was not disrupted even after 5.5 years of exposition in steam turbine environment.
The technology of preparation and subsequent use of nanoparticles is currently a very actual topic, because these particles may have different properties opposite to the conventional materials from which these particles are produced. This article is focused on the production and application of titanium dioxide nanoparticles produced using different methods and their application to the PTFE matrix to create the functional composite coating. The polymorphic compound, described in this article, was chosen, because it has good catalytic properties for subsequent use. In this article, three possibilities of production of nanoparticles are presented. Each of these methods produces a specific particle shape, size, and specific morphology. This also implies the subsequent properties that these different particles have. In the article is also described the use of particles, specifically their application to a PTFE coating. The article presents the process of composite coating preparation. This composite coating is developed for application to an aluminium substrate (silumin) for a particular application in the practice. Subsequently, it was observed the uniformity of the distribution and anchoring of these particles in the coating across the sample surface. In this paper we present the results from the measurement of the coefficient of friction as a function of temperature and the measurement of the nano hardness of the coating.
Datum: 23.5.2019
This paper includes the microstructural and wear characterization of WC-10Co4Cr coating on AZ91 magnesium alloy. Using the scanning electron microscopy and X-ray diffraction analysis it was determined that the microstructure was formed by WC particles, CoCr matrix, present Co3W3C mixed carbide, W2C, and free carbon. The presence of W2C and free carbon indicates the partial decarburization during the spraying process. The microhardness of HVOF-sprayed coating was 1480 ± 80 HV 0.05, which is approximately 20× higher when compared to AZ91 alloy. The friction coefficient values with the subsequent weight loss of the coating and magnesium substrate were determined. It has been proven that HVOF-sprayed WC-CoCr coating can protect the magnesium substrate from the wear.
Metal products with ttextured polymer coatings are distinguished by high strength, durability and esthetic qualities, which give to building structures (roof, etc.) a natural and noble appearance. At modern metallurgical enterprises, the correspondence of the color and texture of the polymer coating with the required parameters (color difference, gloss, etc.) is estimated often visually (“by eye”), without the use of magnifying devices. At present, the development of a methodology for comparison of optical properties of such coatings of metals with a standard is actual. In this paper, the optical microscopy method was used to investigate the surface of metal-rolled samples with the textured polymer coatings of “steel silk” type. The dependences of the number of defects ("stars"), their parameters and the distribution over the surface (concentration of stars and the number of their rays) are analysized for the polyester coatings samples obtained under different thickness of the facial layer.
The paper shows the effect of thermo-chemical treatment: hardening, titanizing and boronizing of steel grade 56Si7 and 41CrAlMo7 applied for the production of yarn guides used in the textile industry. During the investigations the impact of treatment on the structure change, thickness, hardness and wear resistance of the achieved surface layers were determined. Study of the surface layer was conducted using both optical and scanning microscope. The effectiveness of carried out thermo-chemical treatment was verified in relation to the yarn guides working in industrial conditions. It has been proved that although the best results (highest hardness) was achieved after titanizing, also boronizing process guarantees sufficient wear resistance. The results of the research will be used to optimize the guides’ production process including friction and economic parameters.
Beer is a widely consumed alcoholic beverage throughout the world and global production figures have shown an increase in trend during the last decade. Many failures and corrosion problems encountered in brewery and fermentation process due to corrosivity of fluids which are rather acidic and also contain live microfauna. Presence of yeast and chloride ion can cause not only pitting corrosion but also microbiologically induced corrosion which lead to biofouling and failures. In this study, the effect of fermentation products on corrosivity of copper and three austenitic stainless steel is evaluated by electrochemical methods. The metallic samples put into the fermenter vessel and several electrochemical impedance spectroscopy (EIS) tests performed during the fermentation and after that samples were removed from the fermenter and examined by optical microscope (OM) for detecting biofilm and corrosion products. Results showed that EIS curves have changed during the fermentation due to corrosion and biofilm formation.
Sputter-deposited Zr/Nb nanometric multilayer films with a periodicity (L) in the range from 6 to 167 nm were subjected to carbon, silicon and copper ion irradiation with low and high fluences at room temperature. The ion profiles, mechanical proprieties, and disordering behavior have been investigated by using a variety of experimental techniques (Secondary Ion Mass Spectrometry - SIMS, nanoindentation, X-ray diffraction - XRD, and scanning transmission electron microscopy - STEM). On the STEM bright field micrographs there is damage clearly visible on the surface side of the multilayer; deeper, the most damaged and disordered zone, located close to the maximum ion concentration, was observed. The in-depth C and Si concentration profiles obtained from SIMS were not affected by the periodicity of the nanolayers. This is in accordance with SRIM simulations. XRD and electron diffraction analyses suggest a structural evolution in relation to L. After irradiation, Zr (0002) and Nb (110) reflexions overlap for L=6 nm. For the periodicity L> 6 nm the Zr (0002) peak is shifted to higher angles and Nb (110) peak is shifted to lower angles.
The paper presents the results of electrolytic-plasma surface hardening (EPSH) of steel 40KhN. The optimal electrolyte composition for EPSH of 40KhN steel containing 10 % sodium carbonate and 15 % carbamide, which does not cause the surface layer to erosion, oxidation and decarburization, is determined. As a result of EPSH, a modified layer was obtained with increased hardness and wear resistance. We studied the changes in the microhardness of the surface layer of steel 40KhN after the EPSH, as well as the dependence of the microhardness on the duration of the effect of the electrolyte plasma. The paper presents tests for wear resistance of samples before and after electrolytic-plasma surface hardening. Tests have shown that the treated samples show a significant decrease in wear rate compared with the original sample. To clarify the structural factors affecting the wear resistance of steel, the structural-phase states of the hardened surface layers of steel 40KhN were investigated. X-ray structural analysis showed that in the initial state the α-phase and cementite (Fe3C) are present in the structure of 40KhN steel. After the EPSH, diffraction patterns showed a broadening of the interference lines from the crystallographic plane (110). The broadening of the interference line (110) is associated with an increase in the density of dislocations and the formation of martensite and is determined mainly by the tetragonal nature of martensite.
VHX is used by 60.000 companies across the whole world and one of its main application is metal.VHX can do visual inspection of any metal part up to magnification of 5000. It inspects defects on weldings and soldering. Pits and dents, scratcher or any other anomalies. Furthermore, with VHX we can perform 2D/3D analysis, grain analysis, topography, profile measurement and depth measurement. Possibility of flexible observation, fully focused hi quality images and clever reporting is making this device one of the most popular in field.
Datum: 24.5.2019
The demand to discover hard or ultrahard material always a hot topic scientifically and industrially. The borides of the transition metals are one of the attracting areas for hard material. Diborides are intensely under focus, on the other hand, with its super hard character tetraboride of the tungsten is deserve more attraction. Bulk WB4 was synthesized with the hardness over 46 GPa. The deposition of ultrahard WB4 thin film co-sputtered from tungsten and boron target was not reported yet.
In this study, the WB4 thin film was deposited from the co-sputtered tungsten and boron targets and mechanical property of WB4 thin film was investigated. The thin film was synthesized on Si (100) substrate from tungsten and boride targets by using a DC and RF power to targets, respectively. Before the deposition of 800 nm thick WB4 thin film, 70 nm thick tungsten buffer layer was deposited on the substrate in order to increase adhesion of the film to the substrate. The stoichiometry of the WB4 thin films was investigated by using X-ray photoelectron spectroscopy (XPS). XPS analysis findings imply that the chemical composition of the films can be controlled by co-sputtering and the B:W atomic ratio 4 was achieved. The mechanical property of the deposited film was investigated with nano-indentation technique. Nano-hardness measurements indicate that WB4 thin film deposited on an electrically grounded substrate at 300°C has the average indentation hardness, HIT, 41,95±4,16 GPa under an applied load of 5 mN. As a conclusion, in this study, ultra hard WB4 thin film was deposited from co-sputtering of tungsten and boride targets.
The corrosion inhibition of aluminium and steel in the hydrochloric acid solution by 1-octyl-3-methylimidazolium bromide, 1-octyl-3-methylimidazolium hydrogensulphate and 1-dodecyl-3-methylimidazolium bromide was investigated using electrochemical and weight loss methods. The qualitative surface analysis was carried out. All the imidazolium salts under investigation act as mixed type inhibitors with predominantly cathodic action on aluminium and predominantly anodic action on steel. The inhibition efficiency of 1-octyl-3-methylimidazolium hydrogensulphate was higher than 99 % for aluminium but decreased with time rapidly. The surface analysis elucidated the differences between the inhibition action on the mild and stainless steel. The Gibbs energy of adsorption was calculated by means of the Langmuir isotherm.
Metals and alloys with extremely low melting point are an interesting group of functional materials with a multitude of applications, including stretchable and elastic electronics, soft sensors [1] and as a heat transfer material in different systems like computer chips, nuclear reactor or for high power LED [2]. Liquid metal alloys can be also used indirectly as a mean to obtain 2D materials. In a new technique developed at RMIT University, called touch printing, the oxide layer formed on a melted metal can be transferred onto a substrate [3]. In this case we propose the use of non-toxic liquid metal alloys based on gallium, to carry out the synthesis at room temperature, as gallium based alloys are known to readily oxidize. We prepared nanometric multicomponent layers on different substrates including glass, silicon dioxide, silicon and PDMS from Ga-Sn-Zn eutectic alloy. The prepared materials were examined using optical and transmission electron microscopy, XPS and AFM. We determined it is possible to obtain nanometric mixed oxide layers with approximately a thickness of 2-3nm at room temperature.
ACKNOWLEDGEMENTS: The research was co-financed by the European Union from resources of the European Social Fund (Project No.WND-POWR.03.02.00-00-I043/16).
REFERENCES: [1] M.D. Dickey. Advanced materials 29.27 (2017): 1606425.; [2] A. Dobosz, et al. Journal of Chemical & Engineering Data 64.2 (2018): 404-411.; [3] A. Zavabeti, et al. Science 358.6361 (2017): 332-335.
The paper focuses on a detailed analysis of chemical heterogeneity of Inconel 625 overlays with an increased molybdenum content deposited by laser cladding. Fifteen samples of laser overlays on S355J2 steel were prepared, each with an area of 90×140 mm. The thickness of the steel substrate was 50 mm. During the laser cladding process, the temperature field on the face of the substrate was monitored by means of a thermal imaging camera. The surfaces of the Inconel 625 overlays were then machined to their final thickness. Corrosion potential, polarization resistance and corrosion rate in selected areas of laser clads were determined by the potentiodynamic corrosion test. These data were correlated with the temperature profiles during laser cladding and with microstructures of the overlays.
In the present work, the influence of polymorphic transformations on the porosity of plasma sprayed products produced from pure aluminum oxide was investigated. Scanning electron microscopy, quantitative X-ray diffraction analysis, and X-ray computer tomography are used to quantify the porosity. It was established that the plasma sprayed products is a mixture of α, γ and δ aluminum oxides with different densities. When heating, these phase modifications undergo the polymorphic transformations which are accompanied by change in the volume. Opposite variations in the volume of the modifications can lead to both decrease and increase in porosity of material as the temperature of heat treatment increases. It was shown that the non-monotonic behavior of temperature dependence of the porosity is shown to be steadily repeated; this is related to the occurrence of polymorphic transformations. This allows us to change purposefully the porosity of plasma sprayed pure aluminum-oxide products by heat treatments.