Papers by Keyword: Roughness

Abstract: The need to reduce the cost and, therefore, the processing time of metallic materials has pushed academia and industry toward the use of additive manufacturing (AM) technologies. This paper aims to study the effectiveness of a green electropolishing treatment of AlSi10Mg aluminium alloy components produced using Selective Laser Melting (SLM) technology. The influence of treatment duration in relation to specimen surface polishing and the effect on corrosion resistance were evaluated. Morphological characterizations, roughness measurements and electrochemical tests were performed. Specifically, the study identified a set of parameters to achieve a significant reduction in roughness and an increase in the electrochemical characteristics of the components. Green electropolishing could be a viable post-processing treatment substitute to the classical treatment in which environmentally harmful acids are used.

Abstract: Fused Filament Deposition (FDM) additive manufacturing technology allows the generation of three-dimensional parts by overlapping layers of an extruded polymer. The staircase effect caused by overlapping is well known and makes the manufactured parts have poor surface quality. This problem has been focused on by numerous works trying to optimize the surface quality by studying the process technological parameters or part geometry. Also, post-processing techniques have been developed that improve this roughness, but which involve an increase in manufacturing time and cost. In this work, a methodology to measure the roughness based on laser confocal microscopy is proposed. To evaluate the methodology, an experimental study is carried out that relates the surface roughness of parts manufactured with FDM with the building orientation and the layer height. The main objective of this study is to compare two roughness measurement methodologies: a mechanical measurement with a conventional contact roughness meter, and an optical measurement with a confocal microscope. The contact roughness meter provides a direct value of the roughness of the part wall profile, while the confocal microscope provides an image of the three-dimensional surface of the part wall, which must be processed. The data from the confocal microscope are evaluated with the Internet-based software Surface Metrology Algorithm Testing System (SMATS) developed by the National Institute of Standards and Technology (NIST) of the USA. The SMATS will provide an average value of the roughness of the analyzed surface. The test results with both methodologies are very similar, with an average difference of 5%. These results show the influence of the printed plane inclination angle on the roughness, which is higher for low values of the angle. It can also be seen that this influence decreases for low-layer heights.

Abstract: Ceramic tools are a feasible solution for machining hard steels due to their excellent performance in high-temperature environments, which improves productivity. However, the high cutting speeds achieved with ceramic tools can generate cutting temperatures so high that they damage the surface roughness of the component. Therefore, this study aims to analyze the influence of different texturing inclinations on the final roughness of the component and the cutting forces during cutting on Al₂O₃ with TiC for the turning of 1.2990 cold work tool steel. The experimental setup involved testing five different texture grooves inclinations on the rake face of CNGA 120408 inserts, with a recommended cutting speed of 180 m/min, feed of 0.15 mm/rev, and a depth of cut of 0.5 mm. The tests were carried out in dry conditions. Results showed that the textured tools produced lower cutting forces (8%) and better surface roughness (improvement of 16% for R_a and 18% for R_z) than the reference tool without texture. Therefore, texturing inclinations can be used to mitigate the impact of high cutting speeds on the component during ceramic tool machining.

Abstract: Nanostructuring of the surface occurs after annealing at high temperature of 4H-SiC samples. The surface morphology becomes needle-shaped like black silicon. The roughness of the surface also increases due to annealing and a slight etching of nanostructured zones occurs with an accentuated phenomenon at the boundaries. Electroluminescence is obtained by applied forward bias on fabricated PIN diode structures with localized nanostructurated windows in surface. Light intensity seems to be more sensitive to the initial orientation of the substrate and less to the annealing temperature in the 1500°C-1700°C range.

Abstract: In order to research the relation between fracture and texture conditions of PEEK thrust bearing in water, the rolling contact fatigue, RCF test was carried out. And then, the specimen after test was observed with a laser confocal microscope. Three types of surface damage: single crack, flaking and multiple crack: were ob-served. Arithmetic Average Roughness Height, AARH’s around single crack and no-damaged area were calculated. AARH’s in these two areas have no sig-nificantly different each other. This means the effect of cracks on roughness was negligible, and vice versa. The changing of AARH during the test was also dis-cussed. AARH’s both of failure and non-failure specimens were decreased dur-ing RCF tests. AARH Range of non-failure specimens after test included that of the failure specimen. It indicated AARH was not dominated the condition failure of PEEK bearing in water. On the other hands, the load had a clear threshold. This means the failure of PEEK bearing in water is strongly affected by load.

Abstract: TBCs (Thermal Barrier Coatings) are multilayer structures usually consisting of a ceramic layer, known as top coat, arranged on a connecting layer, known as bond coat, which, in turn, is arranged above the substrate to protect. These structures are applied in hot section parts of gas turbine engines for providing thermal protection. During the component life, some oxidation end/or wear phenomena can occur, therefore the TBC is generally removed and then reapplied. To simplify the manufacturing process making it more cost effectiveness, the aim of this work is to study the possibility to repair a TBC system by removing the only damaged layer by using non-conventional processes and analyzing in detail the morphological roughness to ensure a good adhesion between the layers.

Abstract: Sustainability is becoming a central pillar of manufacturing and Additive Manufacturing (AM) processes, thanks to their potentialities, seem to open a new path to reduce the environmental footprint. However, the surface finishing of AM parts is hardly ever adequate for high performances applications so post-process treatments are required. Thus, the assessment of sustainability should inevitably consider both steps. In this study, a Ti6Al4V cylindrical sample was firstly manufactured by Electron Beam Melting (EBM) and then machined by turning as post-treatment process. Surface roughness was measured either before and after the machining process both along the direction parallel and that perpendicular to the axis of the cylindrical sample and a Ra reduction of 84.14% and 95.74% were obtained, respectively. To evaluate the goodness of the machining process from the sustainability perspective, the Specific Energy Consumption (SEC) was calculated to evaluate the unit energy consumption for removal the mass unit. Moreover, power trends during the two turning passes have proved to be useful in understanding the different stages of the machining process, the cutting forces involved, and the amount of material removed.

Abstract: Encapsulating SiC with a carbon layer (C-cap) is a widely used technique to avoid step bunching during post implantation annealing. In this work we propose a mechanism that explains the roughening that the surface unavoidably undergoes during annealing under the C-cap. We investigated the reactions occurring at the interface between 4H-SiC and the C-cap by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and atomic force microscopy carried out at different stages of the sample processing: just after annealing, after C-cap removal in dry Oxygen, and after cleaning in buffered oxide etch solution. Our observations show that, even though the C-cap roughens for increasing annealing temperature and time, it is not visibly damaged even after 1950 °C 30 min annealing. After the C-cap removal the 4H-SiC surface was covered by a network of clusters that are eventually removed by buffered oxide etch solution. This occurrence suggests that, during the post-implantation annealing, the 4H-SiC surface decomposes and the escaped Si and C atoms are trapped inside the C-cap or at the interface between 4H-SiC and the C-cap. While C clusters are etched off in the dry O₂ atmosphere, the Si clusters oxidize and form SiO₂ nanoparticles which are finally etched by buffered oxide etch.

Abstract: This article presents the results of experimental studies of the effect of processing conditions on the corrosion resistance of polished parts made of stainless chromium-nickel steel of austenite class 12X18N10T. It is established that the introduction of the ultrasonic field energy into the shaping zone during grinding can increase the corrosion resistance of parts by 12-15 %, depending on the elements of the grinding mode. The latter is explained by a significantly lower heat-force stress during processing, which, in turn, leads to a decrease in the magnitude and depth of distribution of technological residual tensile stresses along the surface layer.

Abstract: The article provides information on the application of statistical methods of product quality management to the analysis of the process of obtaining paint and varnish coatings with desired properties. A correlation has been established between the standard deviations of the roughness indicators of the coating surface and the surface to be painted. The relationship between the standard deviations for the surface roughness of the coatings and the surface to be painted is given. The results of calculating the values of the root-mean-square deviation of the roughness of the coatings and the class of roughness of the substrate surface, providing with a probability of 0.95 a given class of roughness of the coating surface. The calculation results make it possible to choose a more optimal staining mode in order to obtain a smaller spread in the roughness index of the formed coating. This provides a guaranteed level of quality for the painted surface.