| 1. |
- A. B. Marçal, L., et al.
(författare)
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Spatially resolved structural and chemical properties of the white layer in machined Inconel 718 super alloy
- 2024
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Ingår i: Materials and Design. - 0264-1275. ; 239
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Tidskriftsartikel (refereegranskat)abstract
- Inconel 718 is one type of nickel-based alloy used for a large range of applications, including gas turbines and aeroengines components. Although mechanical and thermodynamic properties of this material have been deeply studied in the past years, a method able to investigate local properties of the thin white layer formed on the alloy surface after machining remains challenging. Here, a 90 nm X-ray beam is used to probe the local strain, crystal orientation, and chemical composition of grains in the white layer. Data reveals mosaicity induced by the tool during machining. The high spatial resolution, combined with crystal lattice sensitivity, shows that the average grain size is around 30 nm throughout the white layer, while the strain is anisotropic nearest to the surface. Results provide new insights on the basic properties of the white layer in super alloys, revealing important information about the impact of finish machining which might help to explain fatigue and cracking formation on these materials during their usage phase.
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| 2. |
- Bergs, T., et al.
(författare)
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Digital twins for cutting processes
- 2023
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Ingår i: CIRP Annals. - 0007-8506. ; 72:2, s. 541-567
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Tidskriftsartikel (refereegranskat)abstract
- Collecting and utilizing data in industrial production are becoming increasingly important. One promising approach to utilize data is the concept of digital twin (DT). DTs are virtual representations of physical assets, updated by real data and enhanced by models. This paper provides an overview of DTs for cutting processes. After giving a definition, we discuss requirements derived from representative use cases. As process models are central for DT creation, we present an overview of the latest research as well as conditions for how it can be implemented in industrial environments. The paper concludes with main challenges for future research.
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| 3. |
- Bushlya, V., et al.
(författare)
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Sintering of binderless cubic boron nitride and its modification by β-Si3N4 additive for hard machining applications
- 2020
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Ingår i: International Journal of Refractory Metals and Hard Materials. - : Elsevier BV. - 0263-4368. ; 86
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Tidskriftsartikel (refereegranskat)abstract
- This study present the results of HP-HT sintering, microstructure, properties, and performance of binderless cBN tool material. Within the investigated sintering temperature range of 1900–2600 °C the optimum was found to be 2200–2300 °C. Lower temperature results in incomplete diffusion bonding between cBN grains, while higher temperature results in high degree of recrystallization of initial structure, grain growth, and even formation of hexagonal boron nitride in triple joints. Introduction of stress-inducing β-Si3N4 minor inclusions resulted in high overall mechanical and thermal properties: HK = 41 GPa; KIC = 12.6 MPa·m1/2; λ = 180 W/(m·K). Machining experiments in roughing of hardened tool steels show that binderless cBN material provides high performance in terms of resistance to tool cratering, chipping, and tool fracture.
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| 4. |
- 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. - : 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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| 5. |
- 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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| 6. |
- Fallqvist, Mikael, 1982-, et al.
(författare)
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Mechanical and tribological properties of PVD-coated cemented carbide as evaluated by a new multi-pass scratch testing method
- 2012
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Ingår i: Advances in Tribology. - : Hindawi Limited. - 1687-5915 .- 1687-5923. ; 2012, s. 305209-
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Tidskriftsartikel (refereegranskat)abstract
- A new test method based on multi-pass scratch testing has been developed for evaluating the mechanical and tribological properties of thin, hard coatings. The proposed test method uses a pin-on-disc tribometer and during testing a Rockwell C diamond stylus is used as the “pin” and loaded against the rotating coated sample. The influence of normal load on the number of cycles to coating damage is investigated and the resulting coating damage mechanisms are evaluated by post-test scanning electron microscopy. The present study presents the test method by evaluating the performance of Ti0.86Si0.14N, Ti0.34Al0.66N and (Al0.7Cr0.3)2O3 coatings deposited by cathodic arc evaporation on cemented carbide inserts. The results show that the test method is quick, simple and reproducible and can preferably be used to obtain relevant data concerning the fatigue, wear, chipping and spalling characteristics of different coating-substrate composites. Also, the small size of the test region (the radius of the circular scratch track can be as small as 0.5 mm) makes it possible to perform tests within small restricted areas. Consequently, the test method can be used as a virtually non-destructive test and e.g. be used to evaluate the fatigue and wear resistance as well as the cohesive and adhesive interfacial strength of coated cemented carbide inserts prior to cutting tests.
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| 7. |
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| 8. |
- Gordon, S., et al.
(författare)
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Mechanical integrity of PVD TiAlN-coated PcBN : Influence of substrate bias voltage and microstructural assemblage
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Ingår i: Ceramics International. - 0272-8842.
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Tidskriftsartikel (refereegranskat)abstract
- Polycrystalline cubic boron nitrides (PcBN) have been increasingly used together with PVD coatings, mainly for hard turning operations. Within this context, effectiveness of coated PcBN as cutting tool is usually addressed by evaluation of its machining performance. Meanwhile, studies aiming to assess and understand the correlation between microstructural features and mechanical behaviour of the coating-substrate system are rather limited. Aiming to overcome such lack of information, in this study the influence of substrate bias voltage (−35 V as compared to −60 V) and microstructural assemblage (as a function of cBN content and binder chemical nature) on the mechanical integrity of TiAlN-coated PcBN systems is investigated. In doing so, contact damage response and coating adhesion strength of different coated-PcBNs are evaluated by means of indentation testing using distinct loading conditions (static and sliding) and tip geometries (spherical and conical). Such testing program is complemented by detailed FESEM inspection of the involved failure micromechanisms, as well as microstructural and micromechanical characterization of the deposited films. Results indicate that resistance against crack nucleation and propagation of coated PcBN, induced by either spherical or conical indentation, is enhanced by using harder (high content of cBN particles) and tougher (metallic binder) substrates (H-PcBN). Regarding bias voltage, systems with coatings deposited using a higher value (−60 V as compared to −35 V) show improved adhesive strength, this being particularly true for combinations involving low cBN content and ceramic binder substrate (L-PcBN). Similar beneficial effect was found, but exclusively in coated L-PcBN systems, regarding resistance to radial cracking emergence and to material removal through cohesive-failure chipping induced in Rockwell C tests. Although these findings are linked to the higher compressive residual stresses exhibited by coatings deposited under −60 V bias voltage, the latter does not translate in significant changes in microstructural and intrinsic mechanical properties of the TiAlN coating itself.
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| 9. |
- 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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| 10. |
- Kryzhanivskyy, V., et al.
(författare)
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Experimental study and modeling of the heat flux acting on the tool flank when machining
- 2021
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Ingår i: 18th CIRP Conference on Modeling of Machining Operations (CMMO), Ljubljana, Slovenia, June 15-17, 2021. - : Elsevier BV. - 2212-8271. ; 102, s. 97-102
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Konferensbidrag (refereegranskat)abstract
- Adequate setting of the boundary conditions for the heat equation when modeling the temperature distribution in the cutting tool is one of the key points. The boundary conditions on the tool surfaces can be divided into two groups: conditions that describe heat losses (heat exchange with the environment) and conditions that characterize the heat source that heats up the tool (heat flux from the cutting zone). Additional complexity in modeling is provided by the fact that during cutting the surface on which the heat source acts changes, for example, due to wear on the flank surface. In this paper, a method is proposed for measuring the power of a heat source acting on the flank surface. The hardware of the method includes a sensor equipped tool and specially manufactured inserts that imitate the geometry of worn flank surface. In turn, the software is based on the method of solving the inverse heat conduction problem in metal cutting, which allows restoring the heat flux flowing into the tool by measuring temperature with sensors installed in the toolholder. The experimental plan included inserts with negative and positive rake, different cutting speeds (190, 235, 280 m/min), and feeds (0.15, 0.3, 0.45 mm/rev).
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