Thermal barrier coatings (TBC) are widely used for protection of turbine blades against aggressive thermomechanical and chemical degradation during operation in hot section of aircraft engine. Quality and properties of TBC coating is strictly related to preparation of substrate material (grinding, and rounding off edges, polishing and cleaning). In the article, tumble finishing as method for surface preparation before deposition of thermal barrier coatings has been described. The process was performed for different types of ceramic feedstock and base material in order to obtain homogeneous roughness. Tumbling was carried out using centrifugal polishing machine. The research was divided into three stages. The first one consisted in investigation of the influence of rotational velocity and water flow, on the course of tumbling process. Afterwards, proper type of ceramic feedstock has been selected. During the last stage, ready-to-use recipes for polishing of samples made of for CMSX-4, Inconel® 718 and stainless steel 1.4016 were developed. Key words: tumbling, tumble finishing, TBC, thermal barrier coatings, surface preparation.1. INTRODUCTION Taking into account the actual trends in aircraft engine design, including constant shifting conditions in the hottest section of aircraft engines towards higher temperature and more aggressive thermomechanical and chemical conditions, it is imperative to apply materials characterized by highest mechanical properties and protective coatings providing thermal insulation and chemical barrier for base material. Increasing the operating temperature allows to improve the engine efficiently and reduce fuel consumption and the emission of carbon dioxide [1, 2]. This canalizes the research on modification of engine design in order to improve the resistance to influence of high temperature, oxidizing gases environment and mechanical loads which are present in operating conditions. In the article, the c więcej »
 

Blades and vanes structural components of turbine engines are processed to withstand high temperature during loading conditions of service, fulfilling high standards of quality control and safety for effective use. Therefore, characterization of mechanical properties, such as creep behaviour, are necessary for appropriate control procedures on prediction of exploitation lifetime. The materials mostly used in manufacturing of these components are single crystal nickel-base superalloys. Creep behaviour characterization, composed of creep-rupture tests, were performed on a single crystal rods made of CMSX-4 superalloy obtained at a withdrawal rate of 3 and 5 mm/min. Cylindrical rods were directly solidified in the [001] direction in an ALD Vacuum Technologies investment casting furnace (VIM-IC 2). Then, prepared specimens were tested in tensile creep under constant stress of 248 MPa at a temperature of 982°C. The longitudinal and cross sections from tested samples, were characterized by TEM and X-ray diffraction methods. It was found that all samples showed a similar rupture mechanism. The electron backscatter diffraction (EBSD) measurements showed that octahedral and cubic slip systems were present however, the critical stress was present on {111} planes. It was observed that the cubic slip has the highest calculated Schmid factor along the dendrite cores while the octahedral slip occurs through entire sample volume. Samples obtained at 5 mm/min possess a visible widening of coherent scattering regions as shown in inverse pole figures. The reason of these changes is the fact that higher rate has the greatest probability of creating small angle boundaries, often occurring in the interdendritic channels. Key words: CMSX-4, single crystal, superalloy, creep.1. INTRODUCTION Single crystal superalloys are widely used in the hot section of gas turbines due to their excellent resistant for creep, fatigue and oxidation at high temperature [1]. They ar więcej »
 

In the present work, quantitative and qualitative indicators related to wear have been proposed based on the results of the research conducted on damaged mill rolls working in a modernized rolling mill, as well as the technical data related to rolling. It has been found that previously used mill rolls were worn by two main mechanisms, i.e. abrasive wear and fatigue wear. The fatigue mechanism is the main reason for the rolls being removed from further exploitation. Tribological laboratory tests were performed by means of the T05 tester (a block/ring wear testing system) with the load of 100 and 300 N applied for 2000 s. The 100Cr6 bearing steel with the hardness of 57 HRC was applied as the counter-sample. The X153CrMo12 and 70MnCrMo8-2 steels were used as the research material. The tempering temperature of 100 and 150°C were used for the X153CrMo12 steel and 100°C for 70MnCrMo8-2 steel. It has been shown that the steel characterized in a microstructure composed of primary carbides (X153CrMo12 and previously used material). The role of the primary and secondary carbide precipitations as abrasive particles has been indicated in the work. It has also been proven that increasing the tempering temperature results in an increased wear of the 70MnCrMo8-2 steel. The conducted research allows for a proper selection of the tempering temperature (100°C). This confirms the assumed concept of the proposed roll heat treatment. A verification (monitoring) of the working rolls’ wear was based on the observations of the cracks formed during their usage and the roughness measurements carried out at three locations across the width of the strip. Key words: cold rolling, mill rolls, tribology, tool steel, primary carbides.1. INTRODUCTION Mill rolls working in cold rolling mills wear mainly because of two mechanisms: abrasive wear and fatigue wear. This results from the stresses present during the rolling process [1, 2]. An intensive abrasive wear blocks więcej »
 

The article presents the results of friction and wear testing of ball-and-socket joints, made of ASTM F75 alloy powder, applying the technologies of selective laser melting and spark plasma sintering. The reference material constituted joints produced by machining from a ASTM F1537 LC rod. The tribological tests were carried out using the movement simulator of a spinal motion segment of our own design, in the environment of distilled water. The test results consisted of a comparison of the friction resistance values occurring in the friction couple and comparison of the wear indicators of the upper and lower components, which simulate the tribological system of an intervertebral disc endoprosthesis in the spinal lumbar segment. Analysis of the wear mechanism of the bearing surfaces was performed on the basis of microscopic observations and measurements of friction surface roughness. Regardless of the manufacturing technology, the coefficient of friction varied in the range of 0.25 to 0.30, wherein a median value for all the tested material combinations was in the range of 0.27 to 0.29. The lowest resistance to tribological wear was demonstrated by the joints produced employing spark plasma sintering technology. The wear of the joints produced with this technology was about 20% higher in comparison to those joints formed by selective laser melting, and about 30% higher compared to the joints produced in a conventional manner from ASTM F1537 LC alloy. Observations performed using scanning electron microscopy showed that regardless of the production technology, the dominant type of wear was abrasive-adhesive wear. Unlike the joints produced in a conventional manner, the bearing surfaces of the components produced by means of selective laser melting and spark plasma sintering technologies, there is evidence of fatigue damage. The results call into question the possibility of using alternative technologies in the manufacturing process of endoprosthe więcej »
 

In these studies, the effect of heat treatment on solid bonded AA6061 aluminium alloy has been investigated. The examined material in the form of powder and rapidly solidified ribbons was subjected to pre-compacting and extrusion carried out at elevated temperature. As a reference material, a billet from the solid AA6061 alloy was subjected to the same procedure. Samples of obtained profiles were subjected to the subsequent heat treatment operation. Surface quality and mechanical properties of materials before and after annealing were compared. The increase in mechanical properties was accompanied by a well visible post-heat treatment blistering effect. Key words: heat treatment, solid bonding, aluminium alloy.1. INTRODUCTION High popularity of Al-Mg-Si alloys in the extrusion industry is mainly derived from their unique properties such as high specific strength, good corrosion resistance, and excellent formability. Furthermore, the heat treatability of these alloys allows improving their mechanical properties though at the cost of ductility [1, 2]. Technical literature provides rich information on the kinetics of Al-Mg-Si precipitation strengthening [3÷7]. According to [8], the precipitation sequence can be divided into the following stages: Al SSS → clusters of Si/Mg → GP zones → β″ → (βʹ + U2 + U1 + Bʹ) → β In the early phase of heat treatment, “clustering" of Si and Mg atoms occurs inside the saturated solid solution (Al SSS) and is followed by subsequent dissolution of Mg clusters and formation of Mg/Si co-clusters. These structural changes lead to exothermic effects and changes in electrical properties [4]. GP zones are the first important metallic phase that arises during precipitation strengthening and is stabilized by high silicon content [9]. The major hardening effect in Al-Mg-Si alloys is attributed to the presence of the needle-shaped β″ phase więcej »
 

The manufacturing of surface layers are increasingly used in industry, as the effective method of improving the useful properties of the machine parts. The specific properties of the nitrided layers such as low temperature of process may be an alternative to the commonly used technology like high-temperature carburizing or carbonitriding in the aerospace industry. The article presents the results obtained after nitriding of complex samples made with 32CDV13 steel. As our research improves the properties of surfaces can be controlled by the process parameters as temperature, duration time, composition of the reactive atmosphere, the pressure (vacuum) and the activation of the surface by cathode sputtering process in the initial stage of the treatment. Key words: glow-discharge nitriding, surface layer, structure, phase composition, residual stresses, corrosion and wear resistance, fatigue strength.1. INTRODUCTION The manufacturing technology of diffusion surface layers under glow-discharge conditions on the cathode potential and their modification in the plasma region are increasingly used in industrial technology as an effective method of improving the production of machine parts at a lower cost of manufacturing. Some specific properties of nitrided layers such as: low temperature of process, high value of hardness, wear resistance and fatigue strength can be an alternative to the commonly used high-temperature carburizing or carbonitriding in the aerospace industry. The paper presents the characteristic of structure and mechanical properties of the layers produced under glow-discharge nitriding on cathode potential related to the basic process parameters. Furthermore the results show that the all presented properties of the 32CDV13 steel can be controlled by the process parameters as temperature, duration time, composition of the reactive atmosphere, the pressure (vacuum) and the activation of the surface by cathode sputtering proces więcej »
 

The use of dimethacrylate resin composite in dentistry involves the potential of shrinkage and then stress contraction. This leads in consequence to defects and even secondary caries. The aim of this study was to modify the commercial resin-based composite using selected monomers and to assess the influence of such additives on polymerization stress and bulk mechanical properties. The polymer matrix was modify due to implementation monomers with differentiated chemical constitution. Stresses generated by the filling were calculated on the basis of the theory of elasticity patterns. The depth of cure and microhardness was evaluated as well. On the basis of measurements, it has been found that stress could be reduced even up to a half when composite is chemical modified by adding not less than 0.25 wt % of 1,6-hexanediol dimethacrylate or diurethane dimethacrylate. Key words: dimethacrylate resins, dental composites, stress contraction, chemical modification.1. INTRODUCTION Cuspal fracture and recurrent caries continually are directly causes of failure of resin composite restorations [1÷3]. During solidification of resin composites stress develops at the restoration-tooth interface. The major cause of it is polymerization contraction of both methacrylate filling and the adhesive agent [4, 5]. Other consequences of the contraction stress are extensively reported in the literature [6, 7]. The elimination or significantly reduction of shrinkage during the polymerization processes is one of the major problem in the development of dental composites. Many factors influence contraction stress in dental composites. These can be divided into material formulation factors, eg. monomer structure and chemistry, filler type and amount, filler-polymer matrix interactions etc. [5]. Secondary group of factors are those connected with material polymerization factors, such as polymerization initiators, inhibitors, cavity geometry, curing method, placement więcej »
 

Nanotubular oxide layer of TiO2 was fabricated by electrochemical anodization of Ti-24Nb-4Zr-8Sn alloy in electrolyte containing water, glycerin and ammonium fluoride. Physicochemical characterization was performed in order to evaluate the structural and chemical properties of obtained layer. Variable parameters such as voltage (10 V, 20 V and 30 V) and anodization time (10 min and 40 min) were applied to determine the influence of those factors on the morphology and chemistry of fabricated titania nanotubes. Scanning electron microscopy was used to assay the architecture of obtained nanotubular layer and the impact of anodization parameters on the produced structure. Chemical and structural analysis were conducted by energy dispersive X-ray spectroscopy coupled with scanning electron microscope and X-rays diffraction technique. Obtained results allowed to declare that morphology of the nanotubes depends on voltage applied and duration of the anodization. For higher voltage applied, the nanotubes with bigger diameter are obtained. For layers fabricated at 10 and 20 V, increase in anodization time results in obtaining more homogeneous oxide structure (the diameter distribution is narrow) as well as decrease of characteristic dimensions values (wall thickness and diameter). For structures anodized with 10 V, the average nanotubes diameter was 38 nm while for layer fabricated with 30 V, the average diameter was 101 nm. The most uniform nanotubular structure was fabricated by anodization at 20 V for 40 min. Chemical analysis revealed presence of such elements as titanium, oxygen, niobium and tin. However, thickness of the nanotubular oxide layer is about hundreds of nm, therefore additional examination need to be done to determine whether the nanotubes contains alloying elements (Nb or Sn) or the signal comes from the substrate. In general, the chemical composition of the anodized nanotubes corresponds to the composition of the substrate Ti2448 all więcej »
 

This paper presents an experimental study of rock samples fracturing with pressure from fluids of different viscosity. Fracturing pressure is one of the most important factors influencing effectiveness of a well-stimulation. It influences both the design of the pressure installation and seismic activity of the area. Authors analysed how fluid viscosity influences material resistance to pressure. As the rock type, marble was chosen. Three fracturing fluids were tested: water (20°C), supercritical carbon dioxide (42°C, 10 MPa) and hydraulic oil H46. The obtained results indicate that fracturing fluid viscosity is an important factor influencing the pressure level required to initiate and propagate fractures. The lowest pressure was detected for carbon dioxide (10.0 MPa). For water test pressure was 16.2 MPa while for oil, which has the highest viscosity, it reached 19.2 MPa. Moreover depending on the fluid type, sample damage could be observed in different planes. Key words: fracturing test stand, hydraulic fracturing, rock tensile strength.1. INTRODUCTION Hydraulic fracturing is useful in geotechnical and mining applications [1]. However, the details of fractures initiation and propagation are difficult to foresee. Nowadays, well stimulation is one of the most promising techniques of increasing the yields of wells that produce oil, natural gas, water or steam. Fracturing pressure is one of the most important factors influencing effectiveness of the process. It influences both the design of the pressure installation and seismic activity of the area. Unfortunately, induced seismicity and water contamination cause environmental concerns associated with large scale hydraulic fracturing. It resulted in political efforts to ban legally the technique in many countries around the world. Therefore, application of the lowest fracturing pressure, which is required for proper well stimulation, is very important. The pressure depends on many factors więcej »