Navegando por Autor "Boing, Denis"

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Effect of PCBN tool grade and cutting type on hard turning of high-chromium white cast iron
(Springer Science and Business Media LLC, 2015-06-24) Oliveira, Adilson José de; Boing, Denis; Schroeter, Rolf Bertrand
The turning of mechanical construction and bearing steels is widely carried out using PCBN and oxide ceramic tools, even when materials have high hardness (40 to 60 HRC), reached after quenching and tempering heat treatment. However, mechanical components submitted to severe abrasive loads show, in addition to matrix hardness, the presence of a high-volume fraction of hard particles in the microstructure. Turning materials with a high content of hard particles in the microstructure will result in high rates of abrasive wear or damage to the cutting edges of the tool. Information regarding the turning of materials characterized by a high-volume fraction of carbides in the microstructure is limited in literature. The objective of this study was to determine the performance of two grades of PCBN tools (high CBN and low CBN content with an added ceramic phase) in the turning of high-chromium white cast iron applying continuous and interrupte cutting. Evaluations of tools’ life, wear mechanisms at the tool cutting edges, roughness, and microstructure remaining on the turned surface were carried out. The results show that the grades with low CBN content and the addition of a ceramic phase, the tool life was three times longer than that of the grades with high CBN content. The most interesting result obtained concerns the microstructural modifications in a narrow subsurface layer of the turned material. Carbide fragmentation and alignment in the direction of the cutting shear plane were identified, which may potentiate the use of the material
Effects of different tool material grades and lubri-cooling techniques in milling of high-Cr white cast iron
(Springer, 2020-08-17) Castro, Nicolau Apoena; Oliveira, Adilson José de; Oliveira, Marcos Vinicyus de Araújo; Melo, Anderson Clayton Alves de; Carvalho Filho, Eugênio Teixeira de; Hermenegildo, Tahiana Francisca da Conceição; Boing, Denis
Mechanical components applied in ore crushing, the drilling of oil wells, and soil plowing need to be manufactured from materials with high resistance to abrasive wear, erosion, and corrosion. Typical materials applied under these severe conditions are cold work tool steels, high-speed steels and high-Cr white cast iron (HCWCI), which present a challenge in machining. In milling, the cutting fluid can easily access the cutting region due to interrupted cutting. In this context, coated cemented carbides associated with lubricooling techniques may be an alternative to improve the process feasibility. The aim of this study was to evaluate the effects of different coated cemented carbide grades and lubri-cooling techniques on the tool life and surface residual stress of the milled surface of HCWCI. Therefore, two coated cemented carbide grades associated with two lubri-cooling techniques (flood emulsion and liquid nitrogen—LN2) were applied in milling tests. The results demonstrated the feasibility of using the coated cemented carbide as a tool material in the milling of HCWCI (cutting time longer than 15 min). Furthermore, LN2 increased, by at least a factor of 2, the tool life when compared with flood emulsion. Regarding the milled surface, values above 500 MPa were obtained for the compressive residual stresses with the use of the worn cutting edges and the application of LN2
Evaluation of wear mechanisms of PVD and CVD coatings deposited on cemented carbide substrates applied to hard turning
(Springer, 2020-02-08) Oliveira, Adilson José de; Boing, Denis; Schroeter, Rolf Bertrand
A good understanding of the coating wear mechanism is essential in relation to tailoring the coating properties to the application, with a focus on increasing the tool performance. When a coated cemented carbide tool is applied in processes with high thermal and mechanical loads (e.g., hard turning process), the cutting tool can suddenly collapse with the deterioration of the coating. The focus of this research was to track the sequence of events that leads to the deterioration of coating materials (PVD TiAlN and MT CVD TiCN/Al2O3/TiN), to reveal the real wear mechanisms associated with coated cemented carbide cutting tools applied to hard turning. The tool wear was evaluated by focus variation microscopy (FVM) and scanning electron microscopy (SEM), before and after cutting edge collapse, during the hard turning of quenched and tempered AISI 4340 steel. The mechanisms associated with the progression of wear on MT CVD coatings involve abrasion, crack nucleation, propagation, the formation of crack networks, delamination, detachment between coating layers, and spalling. The deterioration of PVD coatings is related to the abrasion wear mechanism and the high deformation values at the cutting edge, which leads to the nucleation of cracks in the coating, reducing the bonding strength between the coating and the tool substrate, leading to spalling of the coating. The tool life of the PVD coating was three times longer than that of the CVD coating. The wear mechanisms acting on the coating is the main factor that influences the end of tool life
Three-dimensional wear parameters and wear mechanisms in turning hardened steels with PCBN tools
(Elsevier, 2018-03-15) Oliveira, Adilson José de; Boing, Denis; Schroeter, Rolf Bertrand
Hard turning has been applied in a wide range of mechanical components based on ferrous materials. The application of these components is a function of mechanical properties and microstructure – that also has manufacturing process influences, i.e., cutting mechanism. This research aims to discuss the tool wear level and the correlation with the wear mechanisms in turning with PCBN tools, which deals with three steel alloys (AISI 4340, AISI 52100 and AISI D2) and considers six levels of hardness (on the interval from 35 to 60 HRC), applying the novel three-dimensional wear parameters based on Focus Variation Microscope (FVM) to wear evaluation. Considering the wear parameters that represent the amount of material removed from the tool (WRM) and tool affected area (WAA), tool wear intensity and abrasion wear mechanisms have a decreasing trend with the increase of hardness in the range of 35–50 HRC. Above 50 HRC, however, there is a tendency of increased tool wear intensity when steel hardness is increased. The fraction volume of carbides in the steel microstructures intensifies the abrasion wear mechanism. The adhesion wear mechanism showed a reduction with an increase of the steel's hardness – identified by wear parameters WAM (adhered material volume on the tool). Based on crater wear formation, the diffusion wear mechanism had an inverse behavior when compared to adhesion. Better results concerning tool wear can be achieved when turning steels with 50 HRC. It was evidenced that the three-dimensional wear parameters applied open new possibilities to understanding complex and specific phenomena occurring in machining processes, particularly in the machining of hardened steels

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Navegando por Autor "Boing, Denis"