| 1. |
- Chen, Z., et al.
(författare)
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Plastic Deformation and Residual Stress in High Speed Turning of AD730™ Nickel-based Superalloy with PCBN and WC Tools
- 2018
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Ingår i: Procedia CIRP. - AMSTERDAM, NETHERLANDS : Elsevier BV. - 2212-8271. ; 71, s. 440-445, s. 440-445
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Konferensbidrag (refereegranskat)abstract
- A higher gas turbine efficiency can be achieved by increasing the operating temperature in hot sections. AD730™ is a recently-developed wrought/cast nickel-based superalloy which can maintain excellent mechanical properties above 700. However, machining of AD730™ could be a difficult task like other nickel-based superalloys. Therefore, studies are needed with respect to the machinability of this new alloy. In this paper, high-speed turning was performed on AD730™ using polycrystalline cubic boron nitride (PCBN) tools and coated tungsten carbide (WC) tools at varied cutting speeds. The surface integrity was assessed in two important aspects, i.e., surface and sub-surface plastic deformation and residual stresses. The PCBN tools generally showed better performance compared with the WC tools since it led to reduced machining time without largely compromising the surface integrity achieved. The optimal cutting speed was identified in the range of 200-250 m/min when using the PCBN tools, which gives rise to a good combination of machining efficiency and surface integrity. The further increase of the cutting speed to 300 m/min resulted in severe and deep plastic deformation. Meanwhile, a continuous white layer was formed at the machined surface. When turning with the WC tools, the increased cutting speed from 80 m/min to 100 m/min showed very little effect with respect to the plastic deformation on the machined surface. It was found that tensile residual stresses were developed on all machined surfaces no matter when the PCBN or WC tools were used, and the surface tension was generally increased with increasing cutting speed. The tensile layer might need to be modified by e.g., post-machining surface treatments such as shot peening, if taking good fatigue performance into consideration.
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| 2. |
- Courbon, Cedric, et al.
(författare)
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Adhesion tendency of PVD TiAlN coatings at elevated temperatures during reciprocating sliding against carbon steel
- 2015
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 330-331, s. 209-222
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Tidskriftsartikel (refereegranskat)abstract
- This work focussed on assessing the contact conditions driving the adhesion tendency of PVD TiAlN coated cemented carbide during reciprocating sliding against a normalized AISI 4137 carbon steel. A special emphasis is given to the surface topography of the coating. Results are analysed in terms of friction and material transfer over a large range of temperatures (up to 800 °C) and contact pressures. The post-test surface analysis of the specimens is conducted in order to understand the tribological behaviour and elucidate the formation mechanisms of transfer layers. A numerical model is developed to assess the amount of heat effectively transmitted into the first bodies and the temperature of the surfaces in contact.Whereas temperatures close to 400 °C ensure the formation of a stable tribofilm reducing friction, the highest temperatures lead to unstable frictional behaviour. Coating surface topography has been seen to be a major parameter driving material transfer during the first stages of the contact and the formation of a transfer layer. Thin and homogeneous layers are almost instantaneously formed with a polished surface whereas some time is required with a rougher one to form a film. A large amount of the frictional power is dissipated into these layers and high temperatures can be reached at the surface due to frictional heating. Contact pressure is found to be a parameter promoting transfer and oxidation
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| 3. |
- Kryzhanivskyy, V, et al.
(författare)
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An inverse problem for retrieving time dependency of heat flux in metal cutting via linear programming
- 2018
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Ingår i: Procedia Manufacturing. - : Elsevier BV. - 2351-9789. ; 25, s. 287-293
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Tidskriftsartikel (refereegranskat)abstract
- The paper addresses the inverse heat transfer problem, in which the dependence of the flux on time is determined on the basis of the measured temperatures in remote points of the tool body. The nonlinear heat equation is considered since the properties of the tool material are temperature-dependent. The machining time interval is divided into subintervals within which the change in the tool material properties is ignored. Therefore, it possible to consider a sequence of linear programming problems, each of which minimizes the maximum deviation of the measured temperatures from the calculated ones.
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| 4. |
- Kryzhanivskyy, V., et al.
(författare)
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Heat flux in metal cutting : Experiment, model, and comparative analysis
- 2018
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Ingår i: International Journal of Machine Tools and Manufacture. - : Elsevier BV. - 0890-6955. ; 134, s. 81-97
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a proof of time-dependent behavior of heat flux into a cutting tool is built. Its implementation calls for a new method for estimating heat flux, which was developed using an inverse problem technique. A special experimental setup was designed and manufactured to implement the method. A series of dry machining experiments were conducted with high speed steel and cemented carbide tooling. A two-stage procedure was developed to overcome the ill-posedness of the inverse heat conduction problem by transforming it into a well-posed parameter estimation problem. The first stage retrieves the value of the heat flux and specific tool heating energy Et. The second stage parametrizes and compares predefined heat flux behaviors. It was found that the time dependency of heat flux is best described by a decreasing power function.
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| 5. |
- Kryzhanivskyy, V., et al.
(författare)
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Influence of tool material and tool wear on tool temperature in hard turning reconstructed via inverse problem solution
- 2017
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Ingår i: Journal of Superhard Materials. - 1063-4576. ; 39:3, s. 192-202
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Tidskriftsartikel (refereegranskat)abstract
- In this work the cutting tool temperature distribution that develops during turning of hardened cold-work tool steel is modeled on the basis of experimental data. The data obtained from a series of thermocouples, placed on a PCBN insert, into an anvil, and into a toolholder, were used as the input for the model. An inverse problem was solved, where the heat fluxes were computed. The temperature distribution was modeled for the case of new tools, as well as for the case of its development in the course of a tool wear. The reconstructed temperature distributions were in good agreement with the measured data. The heat flux through rake face was found to be reducing with the decrease of thermal conductivity of the tool material.
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| 6. |
- MSaoubi, R., et al.
(författare)
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Microstructure and wear mechanisms of texture-controlled CVD alpha-Al2O3 coatings
- 2017
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Ingår i: Wear. - : ELSEVIER SCIENCE SA. - 0043-1648 .- 1873-2577. ; 376, s. 1766-1778
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, the microstructure and wear mechanisms of texture controlled CVD alpha-Al2O3 layers with (001), (012) and (100) growth textures were investigated in single point turning of C45 carbon steel at low and high cutting speeds. The experimental coatings were investigated by FEG-SEM, EBSD and a combination of FIB and analytical TEM techniques prior to and after machining. Significant texture effects on wear performance of the alpha-Al2O3 coating layers were observed, confirming results from previous wear studies in the context of machining AISI 4140 carbon steel. The wear mechanisms of the coating layers were further interpreted in the light of thermal, mechanical and frictional conditions occurring at the tool chip contact interface. Possible deformation mechanisms of the alpha-Al2O3 layers under the conditions of high pressure and temperatures acting on the tool surface are discussed. The high dislocation density revealed by the TEM observations in the subsurface alpha-Al2O3 layers was attributed to the activation of a basal slip deformation mechanism resulting from the combined action of the shear stress field and high temperature acting on the tool surface. It is suggested that the enhanced and more uniform near surface deformation capability of (001) alpha-Al2O3 is responsible for the improved machining performance. (C) 2017 Elsevier B.V. All rights reserved.
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| 7. |
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| 8. |
- von Fieandt, Linus, et al.
(författare)
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Chemical Interactions Between Cemented Carbide and Difficult-to-Machine Materials by Diffusion Couple Method and Simulations
- 2018
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Ingår i: Journal of phase equilibria and diffusion. - : SPRINGER. - 1863-7345 .- 1547-7037. ; 39:4, s. 369-376
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Tidskriftsartikel (refereegranskat)abstract
- A simple and efficient diffusion couple method is utilized to study the chemical interactions between cemented carbide cutting tools and difficult-to-machine materials (Ti, Ti-6Al-4V, Ni, Inconel 718, Fe, and AISI 316L). The experimental results and simulations probe different chemical interactions between the cemented carbide and work materials. In particular, the formation of a thick TiC layer is observed at the cemented carbide/Ti and Ti-6Al-4V interface while eta-phase is formed at the interface between the cemented carbide and work materials Inconel 718, Fe and AISI 316L. Pure titanium and Ti-6Al-4V both interact strongly with the tool causing formation of TiC and dissolution of WC-grains. Experiments and diffusion simulations confirm bcc-W formation and progressive diffusion of W into bcc-Ti. For both Ti and Fe work materials a dense band of carbides (WC + eta or WC + TiC) forms at the interface, effectively inhibiting further diffusion. Ni does not form any stable carbide and lowers the eta-phase limit in terms of carbon content, wherefore diffusion can occur freely. The diffusion couple method used in this work, corroborated by DICTRA simulations should serve as a useful tool in the detailed analysis of worn tools where chemical wear is dominant.
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| 9. |
- Zhou, J. M., et al.
(författare)
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Surface Characterization of AD730TM Part Produced in High Speed Turning with CBN tool
- 2018
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Ingår i: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; 71, s. 215-220, s. 215-220
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Konferensbidrag (refereegranskat)abstract
- AD730TM is a novel superalloy developed for the hot section part in aero engine and gas turbine machinery with enhanced performance. The material is characterized by its excellent high temperature properties for being an alloy possible to manufacture by cast and wrought process compared to other superalloys in the same class such as Inconel718. The material with higher temperature capability means potentially increased energy efficiency as well as less emission in the new engine design. However, there is lack of information on machinability of the material, especially achievable surface quality under high speed machining. Machining process is commonly employed in the manufacturing of hot section part, such as turbine disc, to obtain the final surface quality and tolerance. Surface quality produced by the machining processes is one of the crucial factors to determine the functional performance and correspondent fatigue life time of the parts. The paper will present the results of surface characterization of the part produced by high speed turning with CBN tool. A series machining tests were conducted in the study. Surface morphology on machined samples were investigated with a scanning electron microscope to assess the surface damages and other surface defects induced by the machining processes. 3D surface topology was also analyzed with an Infinite-focus-variant microscope to correlate with machining condition. In addition, effect of tool wear and cutting parameters, such as cutting speed, will also be discussed in the paper.
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