CT - DEM - Artigos publicados em periódicos

URI Permanente para esta coleçãohttps://repositorio.ufrn.br/handle/1/176

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Improvement of coating adhesion on cemented carbide tools by plasma etching
(Universidade Federal do Rio de Janeiro - UFRJ, 2016-05-04) Alves, Salete Martins; Albano, Wendell; Oliveira, Adilson José de
Surface treatments are one of the main factors to control adhesion between coating and substrate on a cutting tool. Poor coating adhesion on the substrate accelerates the wear progress and decreases tool lifetime due to the pull-out and release of hard abrasive particles between the tool rake or flank face and the workpiece. Mechanical and chemical substrate treatments are used in order to improve the coating adhesion. This study evaluated and compared the chemical and plasma etching effectiveness in the improvement of substrate-coating adhesion, and consequently, tool life of PVD-coated cemented carbide tools. The plasma etching was performed in plasma reactors in which the cations produced collide with the samples and remove from the surface atoms or molecules modifying the topography. In the chemical etching, acid and alkaline solutions were used to remove tool surface material, changing its initial roughness and chemical composition. After these surface treatments, the samples were PVD coated with (Ti,Al)N. To ascertain the effectiveness of the surface treatment, Rockwell B indentation and machining experiments were performed on treated and untreated tools. Tool topographies were analyzed by atomic force microscopy (AFM) and flank wear lands were evaluated by scanning electronic microscopy (SEM). The plasma-treated tool showed better performance in the indentation and turning tests. Therefore, the chemical etching-treated tool showed the highest roughness, but the coating adhesion was poor due to chemical changes on substrate surface. Furthermore, good anchoring is not influenced only by roughness, it also depends on the substrate surface chemical nature
Improvement of coating adhesion on cemented carbide tools by plasma etching
(Springer, 2016-05-04) Oliveira, Adilson José de; Alves, Salete Martins; Albano, Wendell
Surface treatments are one of the main factors to control adhesion between coating and substrate on a cut- ting tool. Poor coating adhesion on the substrate accelerates the wear progress and decreases tool lifetime due to the pull-out and release of hard abrasive particles between the tool rake or flank face and the workpiece. Mechanical and chemical substrate treatments are used in order to improve the coating adhesion. This study evaluated and compared the chemical and plasma etching effectiveness in the improvement of substrate-coating adhesion, and consequently, tool life of PVD-coated cemented carbide tools. The plasma etching was performed in plasma reactors in which the cations produced collide with the samples and remove from the surface atoms or molecules modifying the topography. In the chemical etching, acid and alkaline solutions were used to remove tool surface material, changing its initial roughness and chemical composition. After these surface treatments, the samples were PVD coated with (Ti,Al)N. To ascertain the effectiveness of the surface treatment, Rockwell B indentation and machining experiments were performed on treated and untreated tools. Tool topographies were analyzed by atomic force microscopy (AFM) and flank wear lands were evaluated by scanning electronic microscopy (SEM). The plasma-treated toolshowed better performance in the indentation and turning tests. Therefore, the chemical etching-treated tool showed the highest roughness, but the coating adhesion was poor due to chemical changes on substrate surface. Furthermore, good anchoring is not influenced only by roughness, it also depends on the substrate surface chemical nature
Micro and nanometric wear evaluation of metal discs used on determination of biodiesel fuel lubricity
(ABM, ABC, ABPol, 2014-07-04) Alves, Salete Martins; Farias, Aline Cristina Mendes de; Medeiros, João Telésforo Nóbrega de
The contact of diesel fuel with engine subsystems demands a good wear resistance. Lubricity is an important feature for integrity of injection system and the sulphur composites are primarily responsible for lubrication of the injector nozzle. Biodiesel is responsible for partially restoring the lubricity of diesel fuel that presents low levels of sulphur composites and, furthermore, it causes less pollution than diesel fuel. The lubricity is measured through the wear scar diameter following the ASTM D 975 standards. However, the friction and wear with light loads of micro/nanocomponents are highly dependent on surface interactions that can be evaluated by microscopy techniques. This study aimed to measure and to analyze the biodiesel lubricity and their blends (B5, B20) with diesel by observing the wear scars of discs using the scanning electronic microscopy (SEM), atomic force microscopy (AFM) and micro roughness techniques. The fuels performance was evaluated using HFRR tribometer. The tests conditions were based on standard ADTM D-6079-04. The coefficient of friction was measure during the test. After the test, the worn ball and disc were analyzed by SEM, AFM and profilometer. The results showed that the addition of biodiesel in diesel improve the tribological performance of fuel. Also, the just WSD value is not sufficient to evaluate the lubrication ability of a fuel. Analysis of the worn disc surfaces proved to be compatible with WSD number and also more sensitive to these kinds of fuels, showing mainly the form and intensity of the wear
Surface modification of M2 steel by combination of cathodic cage plasma deposition and magnetron sputtered MoS2-TiN multilayer coatings
(Elsevier, 2020-02) Alves, Salete Martins; Libório, Maxwell Santana; Praxedes, G. B.; Lima, L. L. F.; Nascimento, Igor Oliveira; Sousa, R. R. M.; Naeem, Muhammad Salman; Costa, Thércio Henrique de Carvalho; Iqbal, Javed
Titanium nitride (TiN) is a good choice for the improvement in surface hardness of high-speed steel. Unfortunately, it has low adhesion with substrate and exhibits high friction coefficient; as a result it does not provide sufficient protection against sliding wear in metal-to-metal contact. The adhesion problem can be removed by nitriding process, whereas friction coefficient can be reduced by solid lubrication coating. In this study, an attempt is made to synthesize TiN hard coating as well as solid lubrication coating of molybdenum disulfide (MoS2) using magnetron sputtering, along with substrate pre-treatment by cathodic cage plasma de- position using titanium cathodic cage. The cathodic cage plasma nitrided sample exhibits significantly higher surface hardness, which reduced by solid lubrication coating. The nitrided sample depicts the presence of ironnitrides, TiN and nitrogen diffused martensite phases, whereas coated samples shows the presence of MoS2 and TiN phases. The friction coefficient and machining temperature are dramatically reduced by lubrication coating. This study recommends that the use of cathodic cage plasma nitriding using titanium cathodic cage is beneficial for improved surface hardness, and addition of solid lubrication coating is beneficial for reducing the coefficient of friction and machining temperature by scarifying hardness. As, both the systems are already proven to be appropriate for industrial-scale uses, thus results from this study can be applied for industrial-scale application
The influence of powder preparation condition on densification and microstructural properties of WC-Co- Al2O3 cermets
(Elsevier, 2020-11) Alves, Salete Martins; Leal, E.A.D; Gomes, Uilame Umbelino; Costa, Francine Alves da
This study investigated how powder preparation during WC-10Co production with the addition of 10 wt% Al2O3 influenced its microstructural and mechanical properties. Powders were mixed with a mechanical shaker for 10 min and high energy milling for 2, 6, 10, 20, 30, and 50 h. The powders were then compacted at 200 MPa and sintered in a resistive dilatometric furnace for one hour, under an argon atmosphere, at a heating rate of 10 °C / min, and two sintering temperatures (1400 °C and 1550 °C). XRD and SEM/EDS analyses were carried out for both powders, which were sintered in order to examine their composition and morphology. The sintered powders were also characterized in terms of mechanical properties, densification, and dilatometric shrinkage. The results show that samples milled for 50 h and sintered at 1550 °C exhibited microstructures with denser phases than those of samples mixed in the shaker. The properties measured were around 68%, 45%, −0.30, and 280 HV for relative density, densification, dilatometric shrinkage, and hardness, respectively

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