| 1. |
- Agmell, Mathias, et al.
(författare)
-
Investigation of mechanical and thermal loads in pcBN tooling during machining of Inconel 718
- 2020
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Ingår i: International Journal of Advanced Manufacturing Technology. - : Springer Science and Business Media LLC. - 0268-3768 .- 1433-3015. ; 107, s. 1451-1462
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates machining superalloy Inconel 718 with polycrystalline cubic boron nitride (pcBN) tooling both numerically and experimentally. Particular attention is given to mechanical and thermal stresses in the cutting tool arising from segmented chip formation and associated forces and temperatures. The temperature dependence of the mechanical properties of pcBN has been investigated and incorporated into a numerical model. In order to capture the dynamic loads due to a serrated chip formation, the Johnson–Cook damage model has been used. The extreme deformations during a machining process often results in a numerical difficulties due to a distorted elements. This paper uses the coupled Eulerian–Lagrangian (CEL) formulation in Abaqus/Explicit, where the workpiece is modelled with the Eulerian formulation and the cutting tool by the Lagrangian one. This CEL formulation enables to completely avoid mesh distortion. The finite element simulation results are validated via comparison of the modelled static and dynamic cutting forces and thermal loads induced into the cutting tool. The numerical model predicts a temperature of 1100–1200 ∘C at the cutting interface, which is in line with experimental determined data. The principal stresses at the rake up to 300 MPa are recorded, whereas higher level of stresses up to 450 MPa are found in the notch region of the tool, well correlated with experimental observation.
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| 2. |
- Bjerke, Axel, et al.
(författare)
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On chemical interactions between an inclusion engineered stainless steel (316L) and (Ti,Al)N coated tools during turning
- 2023
-
Ingår i: Wear. - 0043-1648. ; 532-533
-
Tidskriftsartikel (refereegranskat)abstract
- Non-metallic inclusions offer one of the most effective routes for improving the machinability of steels. However, the wear-reducing mechanisms activated by such inclusions are not fully understood. The interactions are notoriously difficult to predict due to the wide variety of steel grades, cutting conditions, and tool materials employed in industry. The interaction between PVD (Ti,Al)N coated cemented carbide tools, non-metallic inclusions, atmospheric oxygen, and the stainless steel 316L in a turning operation is therefore investigated here as a case study. The study includes turning experiments, nanometer resolution microscopy, and thermodynamic calculations. The paper explains how not only too high a contact pressures hinder the formation of protective deposits at the tool edge, but also how too low a contact pressure leads to excessive wear. A range of conditions specified in this paper must therefore be met for the two observed protective non-metallic inclusions Mg1Al2O4 and Al2Ca2Si1O7 to be preferentially deposited on a tool. Hence the coating wear is experimentally investigated, explained, and a thermodynamic calculation method for predicting the protective or degenerative potential of a deposit on the coating is presented.
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| 3. |
- Bjerke, Axel, et al.
(författare)
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Onset of the degradation of CVD alpha-Al2O3 coating during turning of Ca-treated steels
- 2021
-
Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 477
-
Tidskriftsartikel (refereegranskat)abstract
- The ability to control the shape, distribution and composition of non-metallic inclusions has had an important impact on many aspects of steel making. One such impact is on the machinability. Ca-treatments have shown to be able to reduce the abrasiveness of oxide inclusions, improve chip-breaking and lead to formation of deposits that reduce tool wear. However, machining Ca-treated steels with Al2O3 coated cemented carbide tools has not been as advantageous as expected. This study investigates the mechanisms behind the anomalous wear of Al2O3 coatings when turning soft Ca-treated steels. Longitudinal turning tests at a range of speeds (vc = 100-600 m/min) show rapid localized degradation of the Al2O3 coating limited to the sliding zone. Detailed analysis of the degradation mechanisms was performed using scanning and transmission electron microscopy. The results demonstrate a presence of chemical interactions between the alumina coating and non-metallic inclusions. The interaction resulted in the formation of mainly calcium aluminates and partly alumina-magnesia spinel. In-operando infrared thermography measurements indicate cutting temperatures of 850-1000 degrees C. Thermodynamic calculations give that CaO and MgO readily reacts with Al2O3, while the reaction with CaS requires presence of additional oxygen at these cutting conditions. Additional turning experiments investigate the influence of oxygen by controlling the cutting environment by adding oxygen (compressed air) or removing oxygen (supply argon). These additional tests show that the presence of additional oxygen has a limited impact on the possible Ca-Al2O3 interaction. This demonstrat a potential for further machinability improvements by controlling the chemical interaction between Ca and Mg based non-metallic inclusions and alumina coatings.
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| 4. |
- Bjerke, Axel, et al.
(författare)
-
Thermodynamic modeling framework for prediction of tool wear and tool protection phenomena in machining
- 2021
-
Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 484-485
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Tidskriftsartikel (refereegranskat)abstract
- Chemical, oxidational and diffusional interactions between the tool, chip and cutting environment are known tool wear mechanisms in machining. However, the interaction between tool, coating, workpiece, coolant and atmospheric oxygen can, under favorable conditions, lead to formation of reaction products that retard tool wear. A method with the ability to predict theses interactions, would therefore enable a better control over tool life in machining. An attempt to create such a modelling framework is developed in this study. This method can predict the phase composition and the driving force for degradation and the formation of protective interaction products in the cutting zone. This modeling approach is applicable across cutting processes in which chemical, diffusional and oxidational wear are dominant or present. This framework has been applied to investigate the interactions occurring in the cutting zone during turning of a medium alloyed low-carbon steel (Hybrid Steel (R) 55). A range of degradation events are predicted, as well as the formation of a protective corundum (Al,Fe,Cr)(2)O-3 or spinel (Al, Fe,Cr)(3)O-4 film due to an interaction between the Al-alloyed steel and the environment. Validation of the modeling was performed by studying tool wear and reaction products formed when machining with ceramics, PcBN and coated carbide tooling. Inserts are studied by the use of scanning and transmission electron microscopy, after cutting tests were performed. Additional tests were performed in different environments (dry, argon and coolant). The results confirmed the model predictions of oxidation and diffusion wear as well as the formation of an (Al,Fe,Cr)(3)O-4 tool protection layer. Thus, the proposed thermodynamic framework seem promising to serve as a predictive instrument for the correct pairing of existing tool and workpiece combinations and cutting parameters, or for tailoring respective material compositions for intentional formation of a tool protection layer. As well as guidance on how to apply present and future kinetic models when concurrent interaction mechanisms are present. Which lead to a reduction and minimization of costly experimental machining tests.
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| 5. |
- Bjerke, Axel, et al.
(författare)
-
Understanding wear and interaction between CVD alpha-Al2O3 coated tools, steel, and non-metallic inclusions in machining
- 2022
-
Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 450, s. 128997-
-
Tidskriftsartikel (refereegranskat)abstract
- The aluminum oxide-coating on cemented carbide tools used for metal cutting have been regarded as inert during cutting of steels. Because diffusional dissolution is not possible. Chemical degradation of aluminum oxide coatings is often overlooked, especially in the presence of ambient oxygen and non-metallic inclusions. High-pressure diffusion couples, advanced microscopy, and thermodynamics are used to investigate and predict the chemical degradation of aluminum oxide-coated tools. During interactions with steel and different combinations of inclusions with and without ambient oxygen. The results show that alumina is resistant to chemical degra-dation by steel in the absence of oxygen. However, this is not the case when oxygen and non-metallic inclusions are present. These experiments and microscopy together with the thermodynamic calculations allow for the creation of a method and guidelines for chemical wear modeling and steel inclusion engineering when machining with aluminum oxide-coated tools.
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| 6. |
- Bushlya, Volodymyr, et al.
(författare)
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Effect of ageing on machining performance of grey cast iron and its compensation by cutting speed management
- 2024
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Ingår i: CIRP Annals. - 0007-8506.
-
Tidskriftsartikel (refereegranskat)abstract
- Grey cast iron is known for its poor machinability directly after casting, but attains excellent machining performance after ageing. The present work explores the impact of cutting speed on the performance of pcBN machining for non-aged material. Findings suggest that tool wear can be minimized by identifying an optimal cutting speed that supports the formation of a stable Al2O3 and MnS build-up layer (BUL). Insufficient BUL protection accelerates pcBN wear by diffusion, while at very high speeds protective Al2O3 is replaced by weaker (Fe,Mn)2SiO4 and (Fe,Mn)O, and oxidation accelerates tool wear. The higher mechanical properties of aged GCI facilitate generation of high enough temperatures for stable deposition of Al2O3 BUL.
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| 7. |
- Bushlya, Volodymyr, et al.
(författare)
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Influence of oxygen on the tool wear in machining
- 2018
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Ingår i: CIRP Annals - Manufacturing Technology. - : Elsevier BV. - 0007-8506. ; 67:1, s. 79-82
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Tidskriftsartikel (refereegranskat)abstract
- High temperatures generated in machining are known to facilitate oxidation wear. A controlled atmosphere chamber was developed to investigate the effects of oxygen on tool wear and high speed machining tests were conducted on air and in argon. Cemented carbide, cermet and cubic boron nitride tooling was used on alloyed steel, hardened tool steel and superalloy Alloy 718. Machining in argon resulted in higher flank wear, higher cutting forces, and larger tool–chip contact length on the rake face. However, in hard machining, argon atmosphere reduced rake cratering. Transmission electron microscopy of tools worn on air showed formation of nanocrystalline Al2O3 film on the rake when machining aluminium containing Alloy 718, while no oxide films was detectable in the other cases.
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| 8. |
- Bushlya, Volodymyr, et al.
(författare)
-
Tool wear mechanisms of PcBN in machining Inconel 718: Analysis across multiple length scale
- 2021
-
Ingår i: CIRP Annals - Manufacturing Technology. - : Elsevier BV. - 1726-0604 .- 0007-8506. ; 70:1, s. 73-78
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Tidskriftsartikel (refereegranskat)abstract
- Recently, PcBN tooling have been successfully introduced in machining Ni-based superalloys, yet our knowledge of involved wear mechanisms remains limited. In this study, an in-depth investigation of PcBN tool degradation and related wear mechanisms when machining Inconel 718 was performed. Diffusional dissolution of cBN is an active wear mechanism. At high cutting speed oxidation of cBN becomes equally important. Apart from degradation, tool protection phenomena were also discovered. Oxidation of Inconel 718 resulted in formation of γ-Al2O3 and (Al,Cr,Ti)3O4 spinel that were deposited on the tool rake. Also on the rake, formation of (Ti,Nb,Cr)N takes place due to cBN-workpiece interaction. This creates a sandwich tool protection layer forming continuously as tool wear progresses. Such in operando protection enabled counterbalancing tool wear mechanisms and achieved high performance of PcBN in machining.
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| 9. |
- Chen, Zhe, 1987-, et al.
(författare)
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Effect of Machining Parameters on Cutting Force and Surface Integrity when High-Speed Turning AD730™ with PCBN Tools
- 2019
-
Ingår i: The International Journal of Advanced Manufacturing Technology. - : Springer London. - 0268-3768 .- 1433-3015. ; 100:9-12, s. 2601-2615
-
Tidskriftsartikel (refereegranskat)abstract
- The novel wrought nickel-based superalloy, AD 730™, is a good candidate material for turbine disc applications at high temperatures beyond 650 °C. The present study focuses on the machining performance of this newly developed alloy under high-speed turning conditions with advanced PCBN tools. Meanwhile, the machined surface integrity as influenced by cutting speed and feed rate was also investigated. The surface integrity was thoroughly characterized in terms of surface roughness and morphology, machining-induced plastic deformation, white layer formation, and residual stresses. It has been found that the cutting speed and feed rate had a strong effect on the cutting forces and resultant surface integrity. The cutting forces required when machining the alloy were gradually reduced with increasing cutting speed, while at 250 m/min and above, the flank tool wear became stronger which led to increased thrust force and feed force. A higher feed rate, on the other hand, always resulted in higher cutting forces. Increasing the cutting speed and feed rate in general deteriorated the surface integrity. High cutting speeds within the range of 200–250 m/min and a low feed rate of 0.1 mm/rev are preferable in order to implement more cost-effective machining without largely reducing the surface quality achieved. The formation of tensile residual stresses on the machined AD 730™, however, could be of a concern where good fatigue resistance is critical.
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| 10. |
- Childerhouse, Thomas, et al.
(författare)
-
Machining performance and wear behaviour of polycrystalline diamond and coated carbide tools during milling of titanium alloy Ti-54M
- 2023
-
Ingår i: Wear. - : Elsevier BV. - 0043-1648. ; 523
-
Tidskriftsartikel (refereegranskat)abstract
- Polycrystalline diamond (PCD) is currently under development as a new generation of cutting tool material for titanium alloy machining applications. The unrivaled high temperature hardness possessed by PCD offers the potential for higher levels of productivity compared to tungsten carbide, the current industry standard tool material, through facilitating higher cutting speeds. This study investigates the performance of various PCD tool grades during square shoulder milling of Ti-54M. The influence of PCD grain size on dominant wear mechanism has been established, revealing that a smaller, sub 1 μm, grain size offers improvements in tool life due to superior fracture toughness compared to larger grained material. For fine grained PCD, loss of tool material through a cyclic process of workpiece adhesion followed by grain pull-out was identified to be the predominant wear mechanism, contrasting the mechanical fracture dominated wear observed for the larger grained PCD grades. The influence of insert microgeometry was also investigated through honing of the cutting edge radii. An increased tendency for edge fracture was demonstrated when machining with larger radii tooling which was attributed to increased cutting forces. Finally, the study has compared the surface integrity response of the workpiece following PCD and carbide machining, revealing considerably lower levels of microstructural damage and cutting forces when machining with PCD. This highlights the potential benefits of PCD in finishing applications, whereby high speed machining can be employed to reduce the impact on component surface integrity.
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| 11. |
- Childerhouse, Thomas, et al.
(författare)
-
Rapid acquisition of digital fingerprints of Ti-6Al-4V macrotexture from machining force measurement data
- 2024
-
Ingår i: Materials Characterization. - 1044-5803. ; 207
-
Tidskriftsartikel (refereegranskat)abstract
- Titanium alloys display anisotropic deformation properties due to the hexagonal close-packed (hcp) crystal structure of the α-phase. When subjected to localised deformation during machining, this behaviour influences fluctuations in the cutting force response of the material as the tool encounters grains of different orientations. In this research, cutting force signals acquired during face turning of Ti–6Al–4V possessing a lamellar α colony structure have been spatially mapped demonstrating the ability to identify microstructural features such as prior-β grain boundaries, grain boundary α, and α colonies. Measured cutting forces have been correlated to texture using orientation information acquired from large area EBSD analysis. A relationship between the misalignment of the crystallographic a slip vector with respect to the cutting direction and the passive cutting force response has been established, demonstrating a rise in cutting forces as this misalignment is increased. This novel approach to in-process materials evaluation offers manufacturers the potential of a powerful digital quality assurance tool, with the results presented here demonstrating the possibility for rapid characterisation of entire component surfaces, revealing microstructural features, and inferring the crystallographic orientation of macrotextured regions in Ti–6Al–4V.
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| 12. |
- Childerhouse, Thomas, et al.
(författare)
-
The influence of machining induced surface integrity and residual stress on the fatigue performance of Ti-6Al-4V following polycrystalline diamond and coated cemented carbide milling
- 2022
-
Ingår i: International Journal of Fatigue. - : Elsevier BV. - 0142-1123. ; 163
-
Tidskriftsartikel (refereegranskat)abstract
- Accurate fatigue life predictions of titanium alloy components requires an understanding of how the machining affected metallurgical and micro-mechanical subsurface condition influences fatigue crack nucleation and growth. This study investigates the influence of surface integrity features generated during carbide and high-speed polycrystalline diamond machining on the fatigue behaviour of coarse and fine-grained Ti-6Al-4V. Mechanically induced compressive residual stresses, promoted by higher feed rates and the larger cutting edge radii of carbide tools, have been demonstrated to provide an overriding enhancing effect on fatigue life due to crack initiation suppression and reducing the deleterious effects of microstructural deformation and surface imperfections.
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| 13. |
- Emmanuel, Max, et al.
(författare)
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Fracture Energy Measurement of Prismatic Plane and Σ2 Boundary in Cemented Carbide
- 2021
-
Ingår i: JOM. - : Springer Science and Business Media LLC. - 1047-4838 .- 1543-1851. ; 73:6, s. 1589-1596
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Tidskriftsartikel (refereegranskat)abstract
- The grain boundary network of WC in WC-Co is important, as cracks often travel intergranularly. This motivates the present work, where we experimentally measure the fracture energy of Σ2 twist grain boundaries between WC crystals using a double cantilever beam opened with a wedge under displacement control in a WC-10wt%Co sample. The fracture energy of this boundary type was compared with cleaving {10 1 ¯ 0 } prismatic planes in a WC single crystal. Fracture energies of 7.04 ± 0.36 Jm−2 and 3.57 ± 0.28 Jm−2 were measured for {10 1 ¯ 0 } plane and Σ2 twist boundaries, respectively.
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| 14. |
- Fallqvist, Mikael, 1982-, et al.
(författare)
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Influence of the tool surface micro topography on the tribological characteristics in metal cutting – Part I Experimental observations of contact conditions
- 2013
-
Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 298, s. 87-98
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Tidskriftsartikel (refereegranskat)abstract
- The influence of surface micro topography of CVD α-Al2O3 coatings, deposited on cemented carbide inserts, on tribological characteristics in sliding contact and in metal cutting has been investigated using quenched and tempered steel as counter/work material. Pin-on-disc and turning tests were carried out and post-test characterization using 3D optical surface profilometry and scanning electron microscopy was performed in order to investigate the tribological response of the coatings. The results show that surface micro topography can have a significant impact on the tribological performance of Al2O3 coatings under initial and cutting contact conditions. For both kinds of tests the tendency for transfer of workpiece material strongly increases with increasing coating micro topography. In the pin-on-disc tests, a smooth coating surface significantly reduces the friction coefficient. In the turning tests the contact conditions at the flank face increase with decreasing micro topography. In contrast, no general conclusions can be drawn regarding the influence of coating micro topography on the contact conditions at the rake face. The resulting topography of the turned surface was found to increase with increasing coating topography.
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| 15. |
- Hoseiny, Seyyed Mohammad Hamed, 1980, et al.
(författare)
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The Influence of Heat Treatment on the Microstructure and Machinability of a Prehardened Mold Steel
- 2015
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Ingår i: Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science. - : Springer Science and Business Media LLC. - 1073-5623. ; 46A:5, s. 2157-2171
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Tidskriftsartikel (refereegranskat)abstract
- The machinability performance of a modified AISI P20 steel, heat treated to have the same hardness but three different microstructures, lower bainite, tempered martensite, and primary spheroidized carbides in a tempered martensite matrix, was studied. The microstructures were characterized using light optical and scanning electron microscopy and X-ray diffraction, and mechanical properties were compared by means of tensile and Charpy V-notch impact tests. The influence of microstructure and the resultant mechanical properties on machinability was studied in the context of single tooth end milling operation. The results showed that the material containing primary spheroidized carbides exhibited a superior machinability at the expense of a marginal loss of tensile strength and impact toughness, with comparable yield strength to that of the material containing tempered martensite. By contrast, the material with bainitic mi- crostructure showed the lowest yield strength and the poorest machinability performance while having the highest uniform elongation.
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| 16. |
- Hrechuk, Andrew, et al.
(författare)
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Experimental investigations into tool wear of drilling CFRP
- 2018
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Ingår i: Procedia Manufacturing. - : Elsevier BV. - 2351-9789. ; 25, s. 294-301
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Tidskriftsartikel (refereegranskat)abstract
- Carbon Fiber Reinforced Polymer (CFRP) has highly abrasive microstructure due to carbon fiber reinforcement and requires the use of tool materials with good resistance to abrasive wear. The paper presents a study of tool wear in drilling operation. Drill bits with uncoated and diamond coated cemented carbide and polycrystalline diamond were tested in drilling PAN-based CFRP samples. Registered thrust force, torque, flank wear, cutting edge radius (CER), drilled holes quality are correlated with the tool material type. Experimental results showed existence of CER critical values and flank wear that are affecting acceptable hole quality and CFRP chip structure.
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| 17. |
- Hrechuk, Andrew, et al.
(författare)
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Quantitative analysis of chip segmentation in machining using an automated image processing method
- 2019
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Ingår i: 17th CIRP Conference on Modelling of Machining Operations (17th CIRP CMMO). - : Elsevier BV. - 2212-8271. ; 82, s. 314-319
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Konferensbidrag (refereegranskat)abstract
- Analysis of chip formation is one of the most established and informative methods for description of the cutting process. A number of established techniques ranging from optical to electron microscopy have been developed for analysis of continuous chips. Yet, machining of difficult-to-cut materials is accompanied by segmented chip formation. This paper presents an original algorithm based on image processing of segmented chips that quantifies chip compression ratio, dimensions of segments, segmentation frequency, etc. The algorithm was validated when analyzing chip cross-sections for the cases of orthogonal turning of stainless steel 316L and Inconel 718.
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| 18. |
- Johansson, Daniel, et al.
(författare)
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Assessment of Metal Cutting Tools using Cost Performance Ratio and Tool Life Analyses
- 2019
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Ingår i: Procedia Manufacturing. - : Elsevier BV. - 2351-9789. ; 38, s. 816-823
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Tidskriftsartikel (refereegranskat)abstract
- Critical raw materials (CRM) are extensively used in tools for metal cutting, such as in cemented carbide tools (cobalt and tungsten), because they provide desired characteristics of high fracture toughness and wear resistance. Both academia and industry are examining CRM-free material alternatives, such as tools based on polycrystalline diamond (PCD) or ceramic materials. These materials are generally more cost intensive as compared to cemented carbide but could also provide higher efficiency in terms of material removal rate. Material removal rate and tool costs have a substantial influence on the final part cost. When deciding on tool material, the manufacturing industry is either looking for the most cost effective alternative or the alternative providing the highest productivity output. The purpose of this paper is to provide industry with decision support for selection of tool and cutting data that provide the financial most sound production set-up. This work aims to present a novel methodology combining the Colding tool life model and a previously presented model for cost performance ratio. A previous publication provided a method to assess technological solutions and investments based on final part cost. The developed methodology in this article combines cutting performance and production performance to allow a comprehensive cost assessment for a production process. The assessment includes cutting data, tool life and costs of tooling, quality rejections, process availability, equipment investment, personnel and facility. A case study based on experimental data is presented to verify the proposed methodology.
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| 19. |
- Johansson, Jakob, et al.
(författare)
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Influence of sub-surface deformation induced by machining on stress corrosion cracking in lead-free brass
- 2022
-
Ingår i: The International Journal of Advanced Manufacturing Technology. - : Springer Science and Business Media Deutschland GmbH. - 0268-3768 .- 1433-3015. ; 122:7-8, s. 3171-3181
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Tidskriftsartikel (refereegranskat)abstract
- New stricter regulations on lead (Pb) content in brass for use in certain applications is driving the industry from traditional leaded brass towards Pb-free alloys. However, machining induced surface integrity for such Pb-free alloys and related corrosion resistance are largely unknown. Two Pb-free brass alloys, CuZn38As and CuZn21Si3P, approved for use in drinking water applications, were machined under different cutting conditions, tool geometries and tool wear states. The resulting surface integrity and sub-surface deformation was characterized using nano-indentation, scanning electron (SEM) and ion microscopy, and electron backscatter diffraction (EBSD). The materials resistance to stress corrosion cracking (SCC) was assessed by exposing the machined samples to a corrosive substance in accordance with SIS 117102. The results show that tool wear is the most influencing parameter leading to stronger sub-surface deformation. This was especially pronounced for alloy CuZn38As, where for equivalent depth of deformation, the material exhibited higher degree of work-hardening compared to the other tested alloy. Subsequently, substantial stress corrosion cracking was registered for machined CuZn38As samples. © 2022, The Author(s).
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| 20. |
- Johansson, Jakob, et al.
(författare)
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On the function of lead (Pb) in machining brass alloys
- 2022
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Ingår i: International Journal of Advanced Manufacturing Technology. - : Springer Science and Business Media LLC. - 0268-3768 .- 1433-3015. ; 120:11-12, s. 7263-7275
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Tidskriftsartikel (refereegranskat)abstract
- Lead has traditionally been added to brass alloys to achieve high machinability, but the exact mechanisms at work are still debated. Lead-free brass alternatives could be developed if these mechanisms were better understood. Accordingly, machinability characteristics were investigated for two brass alloys with similar mechanical properties and phase composition, but with very different machining characteristics because one has 3 wt.% lead (CuZn38Pb3) while the other has only 0.1 wt.% (CuZn42). The effect of the lead was investigated using infrared temperature measurement, electron microscopy, secondary ion mass spectroscopy, quick-stop methods, and high-speed filming. Neither melting of lead nor its deposition on the tool rake surface takes place during machining thus confirming its limited lubrication and tribological effects. Instead, the main role of lead is to promote discontinuous chip formation. Lead deforms to flake-like shapes that act as crack initiation points when the workpiece material passes through the primary deformation zone. This effect prevents the development of stable tool–chip contact, thus lowering cutting forces, friction, and process temperature.
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| 21. |
- Johansson, Mats, et al.
(författare)
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Microstructural anisotropy effects on the metal cutting performance of decomposed arc evaporated Ti1-xAlxN coatings
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The spinodal decomposition of cathodic arc evaporated cubic phase c-Ti0.34Al0.66N and c-Ti0.60Al0.40N coatings have been studied before and after continuous turning. By means of analytical transmission electron microscopy, we find that the evolving microstructure of c-Ti0.34Al0.66N, as simultaneously being exposed to high temperature of about 900 °C and high pressure of about 2.5 GPa, spinodally decompose into a spatially periodic, highly oriented and modulated interconnected array of coherent cubic AlN and cubic TiN rich regions along elastic compliant <100> crystal directions. Ti0.60Al0.40N instead decomposes into AlN and TiN rich domains in a more rounded and random microstructure. These effects are both explained by the elastic anisotropy which has earlier been shown to scale with Al content. The different evolving microstructure will lead to a different strengthening mechanism in the coatings during metal cutting and heat treatments, thus a different hardness and wear resistance behaviour.
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| 22. |
- Kantojärvi, Fredrik, et al.
(författare)
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Predicting tool life for side milling in C45 E using Colding and Taylor tool life models
- 2023
-
Ingår i: Advances in Industrial and Manufacturing Engineering. - 2666-9129. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the possibility of using empirical tool life models to predict tool life in a side milling application in a medium carbon steel, C 45E. To do this, an extensive dataset containing 46 data points with different machining parameters are produced. Four different empirical models: Taylor's equation, Colding's equation and Extended Taylor both using depth of cut and feed as well as an Extended Taylor using equivalent chip thickness has been considered. It is found that Colding's equation is best suited to predict the tool life for this application. Furthermore, this paper suggests a novel method to fit the experimental data to the empirical models. Based on the results from previously published papers it is shown that the proposed method performs equally or better to determine the model constants.
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| 23. |
- Kryzhanivskyy, V., et al.
(författare)
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Computational and Experimental Inverse Problem Approach for Determination of Time Dependency of Heat Flux in Metal Cutting
- 2017
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Ingår i: 16th CIRP Conference on Modelling of Machining Operations (16th CIRP CMMO). - : Elsevier BV. - 2212-8271. - 9781510842762 ; 58, s. 122-127
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Konferensbidrag (refereegranskat)abstract
- This study develops the method for solution of inverse heat conduction problem applied to metal cutting. The proposed method operates with a selection procedure involving iterative solutions of heat forward problem. In such formulation, it allows avoiding difficulties associated with ill-posed inverse problems inherent to conventional formulations. Inverse heat problem was transformed into constrained optimization problem via objective function which metrizes the difference between FE and experimental data. Specially designed solid HSS cutting tool with embedded thermocouples was manufactured. The method was validated for the case of orthogonal machining of 6061 aluminum alloy. The numerical simulations were performed with the help of COMSOL Multiphysics and MATLAB scripts. Heat flux exhibits descending trend over the time of the cutting test and closely follows hyperbola function behavior with the average value of q = 4.6 MW/m2.
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| 24. |
- Lindvall, Rebecka, et al.
(författare)
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Degradation of multi-layer CVD-coated cemented carbide in finish milling compacted graphite iron
- 2023
-
Ingår i: Wear. - : Elsevier BV. - 0043-1648. ; 522
-
Tidskriftsartikel (refereegranskat)abstract
- Stricter regulations on emissions and higher demands on engine performance drive automotive industries to replace conventional gray cast iron with compacted graphite iron (CGI). CGI has a higher wear resistance, strength, elastic modulus, and almost double fatigue strength as to gray cast iron, yet the same positive properties make CGI more difficult to machine. This study focuses on finish milling CGI EN-GJV-450 with current industrial standard of tooling: cemented carbide with multi-layer CVD-coating of Ti(C,N)–Al2O3. At cutting speed of 150 m/min a total of 3126 cm3 of material after 190 passes was removed, while 1645 cm3 was removed after 100 passes in case of 250 m/min. Studying the wear evolution at different engagement times demonstrated an accelerated chemical wear of the Al2O3 top coating due to its reaction with MgO-containing inclusions that creates a softer reaction product of (Mg,Fe,Mn)Al2O4 spinel which is abraded and removed with the chip flow. Ti(C,N) coating layer experiences diffusional and mechanical (abrasion, debonding, micro-fracture) wear mechanisms. Exposure of cemented carbide substrate resulted in its rapid wear in the form of cratering and massive material loss on the flank where the latter eventually causes tool failure. The adherence of CGI to WC-Co facilitates diffusional loss of carbon and tungsten from WC grains. Carbon reacts with iron at the interface forming iron carbide, while residual tungsten alloys it thus forming (Fex,W1-x)3C. This phase can reduce the wear rate as it acts as a diffusion barrier, but its high brittleness enables its periodic removal by adhesive wear. Outward cobalt diffusion was also an active wear mechanism that facilitates further diffusion of carbon and tungsten but also weakens the WC-grain bonding, further facilitating adhesive wear by CGI flow. Deposition of oxide inclusions to exposed WC-Co work as an anti-stick for CGI adhesion and thus reduces the wear rate.
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| 25. |
- Lindvall, Rebecka, et al.
(författare)
-
On wear of TiAlN coated tools with and without NbN overlayer in machining titanium alloys
- 2024
-
Ingår i: International Journal of Machine Tools and Manufacture. - 0890-6955. ; 198
-
Tidskriftsartikel (refereegranskat)abstract
- Finding a wear resistant coating for cemented carbide cutting tools in the machining of difficult to cut Ti alloys is a challenge due to their high strength and chemical reactivity. Tool manufacturers recommend physical vapor deposited (PVD) TixAl1-xN (x = 0.4–0.7), and an extra NbN overlayer has shown promising potential. This study explores wear mechanisms of PVD Ti0.45Al0.55N with and without NbN overlayer and its WC-Co substrate in machining Ti alloys. To achieve an accurate understanding of tool-chip-workpiece interaction and related wear mechanisms, several approaches were employed. Tests with controlled variation of cutting speeds were complemented by process freezing experiments using the quick stop method and imitational experiments of diffusion couples. Advanced microscopy techniques were employed for accurate detection of wear products and phenomena across length scale. Findings reveal that any new design of coatings for Ti machining must combine both high mechanical integrity and resistance to diffusional dissolution and oxidation. Observed diffusional loss of Al and N from the coating results in a TiN layer which is mechanically weaker than the original coating, while the NbN overlayer reduces the Al diffusion rate, but NbN is subjected to diffusional dissolution itself. On dissolution, Nb stabilizes β-Ti and thus facilitating loss of Al, but the observed formation of intermetallic Nb3Al at the NbN–Ti interface works as a diffusion barrier. However, brittle Nb3Al can be more easily removed during machining. It was found that the coating retains longest on the edge line and protects the tool edge from failure because substrate cemented carbide wears at a faster rate than the coating with outward diffusion of C from WC grains and Co binder.
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| 26. |
- Lindvall, Rebecka, et al.
(författare)
-
Performance and wear mechanisms of PCD and pcBN cutting tools during machining titanium alloy Ti6Al4V
- 2020
-
Ingår i: Wear. - : Elsevier BV. - 0043-1648. ; 454-455
-
Tidskriftsartikel (refereegranskat)abstract
- The need for increased productivity in difficult-to-machine titanium alloys has pushed manufacturers to examine the potential of ultrahard cutting tool materials such as polycrystalline diamond and polycrystalline cubic boron nitride as alternative solutions to conventional cemented carbide tools. This study examines the performance of such advanced tool materials in high speed finishing machining of Ti6Al4V, with attained PCD superiority compared to pcBN. Wear mechanisms are experimentally investigated based on in-depth microscopic analyses using techniques such as scanning electron microscopy, transmission electron microscopy, electron diffraction and X-ray energy-dispersive spectroscopy. Main wear morphologies were flank wear and cratering in both tool materials. Flank fracture caused by micro-cracking was an additional deterioration mechanism of pcBN tooling. Diamond burn-out, likely in combination with graphitization of diamond, was causing channel like wear morphology. The PCD wear mechanism was diffusion dissolution of carbon in Ti6Al4V. (Ti,V)C diffusional barrier or Tool Protection Layer (TPL) was formed due to reaction of workpiece and tool materials in presence of cobalt. Controlled grain size and increased cobalt content resulted in higher performance as protective caps of (Ti,V)C merged to form a continuous TPL. Similarly for pcBN, (Ti,V)B2 and (Ti,V,Cr)B2 reaction products acted as TPLs which reduced the tool deterioration rate.
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| 27. |
- Lindvall, Rebecka, et al.
(författare)
-
Performance and wear mechanisms of uncoated cemented carbide cutting tools in Ti6Al4V machining
- 2021
-
Ingår i: Wear. - : Elsevier BV. - 0043-1648. ; 477
-
Tidskriftsartikel (refereegranskat)abstract
- The primary tool material when machining Ti6Al4V titanium alloy is uncoated straight cemented carbide. This study examines the performance of these materials during high-speed finish turning, and uses the advanced microscopy methods of SEM, (S)TEM, XEDS, and SAED to explore the fundamental tool wear mechanisms. The wear modes include a combination of flank wear and rake cratering. Four individual TEM lamellae were extracted from the crater and flank of one as-worn tool to investigate the wear mechanisms of cemented carbide exposed to different temperatures and contact conditions. The main wear mechanism identified is temperature-driven diffusion. Outward carbon diffusion occurs from surface WC grains into the adhered Ti alloy, which results in a layer of metallic tungsten. Dissolution of the W layer leads to doping of the α-Ti, thus causing its transformation into the β-Ti phase. At the same time, carbon-depleted WC grains interact with the Co binder, inducing formation of Co3W. Additional wear mechanisms include inward titanium diffusion, resulting in formation of TiC on both sides of the W layer. Simultaneously, TiCo2 is formed in Co-rich regions in the vicinity of the tool-chip interface. These reaction products retard direct dissolution of tool material in Ti6Al4V, thus acting as localized tool protection layers.
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| 28. |
- Lindvall, Rebecka
(creator_code:cre_t)
-
Polycrystalline cubic boron nitride material
- 2023
-
Patent (övrigt vetenskapligt/konstnärligt)abstract
- This disclosure relates to a high cBN content polycrystalline cubic boron nitride, PCBN, material. The binder matrix material comprises 19 to 50 wt. % chromium, or a compound thereof.
|
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| 29. |
- Lindvall, Rebecka
(creator_code:cre_t)
-
Polycrystalline cubic boron nitride material
- 2023
-
Patent (övrigt vetenskapligt/konstnärligt)abstract
- This disclosure relates to a high cBN content polycrystalline cubic boron nitride, PCBN, material. The binder matrix material comprises 2 to 15 wt.% titanium diboride (TiB2).
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| 30. |
- Lindvall, Rebecka, et al.
(författare)
-
Predicting wear mechanisms of ultra-hard tooling in machining Ti6Al4V by diffusion couples and simulation
- 2023
-
Ingår i: Journal of the European Ceramic Society. - : Elsevier BV. - 0955-2219 .- 1873-619X. ; 43:2, s. 291-303
-
Tidskriftsartikel (refereegranskat)abstract
- Conventional cemented carbide is recommended for machining Ti6Al4V. However, polycrystalline diamond (PCD) and polycrystalline cubic boron nitride (pcBN) also show promise. Demands for higher productivity accelerate diffusional dissolution and chemically driven wear mechanisms in these tool materials. This study investigates active wear mechanisms by studying the interactions between Ti6Al4V and PCD, pcBN, and cemented carbide tools in diffusion couples at temperatures from 900° to 1300°C. All tool materials suffered from diffusion to varying degrees, and different chemical reactions occurred. Titanium carbide with minor vanadium alloying (Ti,V)C reaction products act as diffusion barriers when using PCD and cemented carbide, while the reaction products acting as diffusion barrier in pcBN is (Ti,V)B2. The presence of Mo and W in binder sites of pcBN reduces diffusional dissolution of cBN. Diffusion simulations agreed well with microscopy investigations and were enabled by the known temperature and pressure conditions of the static diffusion couples.
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| 31. |
- Lindvall, Rebecka, et al.
(författare)
-
Wear mechanisms in Ti(C,N)-Al2O3 coated carbide during sustainable machining CGI
- 2024
-
Ingår i: International Journal of Refractory Metals and Hard Materials. - : ELSEVIER SCI LTD. - 0263-4368. ; 119
-
Tidskriftsartikel (refereegranskat)abstract
- By replacing conventional gray cast iron (GI) with compacted graphite iron (CGI), automotive industry could keep up with stricter regulations on emissions and demands on higher engine performance. CGI has improved properties as to GI but is more difficult to machine. This study evaluates sustainable machining performance during finish face milling when using minimum quantity lubrication applied vegetable oil, resulting in 8% or 17–23% improved tool life respectively as to dry conditions. The main part of the study investigates the wear mechanisms in commercial Ti(C,N)-Al2O3 CVD-coated cemented carbide. The coating degrades by mechanically induced cracking and fractures, oxidation of adhered CGI inside cracks, diffusional dissolution of Ti(C,N) layer. Formation of softer (Mg,Fe,Mn)Al2O4 spinel is not observed but could be an expected reaction product. Other oxide inclusions, when deposited on cemented carbide surfaces, prevents adhesion of CGI material, and can reduce the wear rate where they are present. CGI adhering to cemented carbide induces diffusional loss of cobalt and carbon that eventually forms (Fex,Co1-x)3C iron carbide at the tool-workpiece interface which can reduce the diffusion rate. Novel findings also relates to the formation of 15 μm deep cracks in the cemented carbide due to inward diffusion of Fe accompanied by its oxidation that speeds up the oxygen ingress and further oxidation of W and Co. Oxidation was found to provide a positive effect when the adhered CGI completely oxidized to form Fe2SiO4 oxide ceramic Tool Protection Layer which slowed down tool material degradation.
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| 32. |
- Liu, Yang, et al.
(författare)
-
Evolution of residual stress when turning a fillet radius in stainless steel
- 2023
-
Ingår i: Journal of Manufacturing Processes. - : Elsevier BV. - 1526-6125. ; 85, s. 216-226
-
Tidskriftsartikel (refereegranskat)abstract
- Most studies have been carried out to investigate the surface integrity induced by metal cutting process. However, the previous studies are limited to a longitudinal turning or orthogonal cutting operations and the residual stresses generated in a fillet radius have been ignored. This study uses a combination of experiments and numerical simulations to study the evolution of cutting forces, temperature, chip morphology, and residual stress distributions while turning a fillet radius in AISI 304. Finite Element (FE) models were developed with a Coupled Eulerian and Lagrangian (CEL) method, where the geometric model of the workpiece was established taking into account the previous machined surface profile at the four specific cutting faces. The model was validated by experimental cutting forces, chip morphology, and residual stress profiles. The changing trend of shape and area of uncut chip cross-section during fillet turning were analyzed to explain the evolution of cutting forces and temperatures. The results show that the cutting force components in cutting speed and tangential directions increase during the early stage of the fillet turning process and decrease after that, while the force in the radial direction shows an increasing trend during this process. The maximum temperature at the machined surface is increased along the tool path. In addition, magnitude and depth of residual stress are slightly changed during the fillet radius turning process, but a reduction of the residual stress profile can still be noticed.
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| 33. |
- Makgae, Ofentse A., et al.
(författare)
-
Visualising microstructural dynamics of titanium aluminium nitride coatings under variable-temperature oxidation
- 2023
-
Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332. ; 618
-
Tidskriftsartikel (refereegranskat)abstract
- Understanding the link between titanium-aluminium nitride's (Ti1-xAlxN) physicochemical properties and structural dynamics during operation is essential to designing and fabricating advanced ceramic coatings. Here, we directly visualise the oxidation of Ti1-xAlxN (for x = 0, 0.18, 0.44, & 0.67) coatings from 100 to 1000 °C using environmental transmission electron microscopy (ETEM) imaging and energy dispersive X-ray spectroscopy (EDX) analysis. The high-frame-rate ETEM movies show that oxidation in TiN proceeds at the grain boundaries and cracks; in contrast, Ti1-xAlxN coatings transform from large as-deposited grains into oxide nanoparticles. Moreover, high-resolution ETEM imaging show the presence of anatase TiO2 at the early stages of oxidation across all compositions. Above ∼ 850 °C, the oxide nanoparticles grow through crystal merging, diffusion and recrystallisation to form rutile TiO2. The EDX elemental maps coupled with secondary electron imaging reveal a uniform TiO2 sublayer decorated with increasing coverage of Al2O3 particles for x = 0.18 to 0.44. In contrast, coatings with x = 0.67 reveal a complete in-plane phase separation of Al- and Ti-oxides, which can rationalise their decreasing long-term oxidation resistance. Finally, the study provides unique insight into the real-time structural dynamics underpinning the oxidation resistance of Ti1-xAlxN coatings.
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| 34. |
- Malakizadi, Amir, 1983, et al.
(författare)
-
The role of microstructural characteristics of additively manufactured Alloy 718 on tool wear in machining
- 2021
-
Ingår i: International Journal of Machine Tools and Manufacture. - : Elsevier BV. - 0890-6955. ; 171
-
Tidskriftsartikel (refereegranskat)abstract
- This study aims to provide a fundamental understanding of the role of microstructural characteristics influencing tool wear when machining Alloy 718 fabricated using Powder Bed Fusion (PBF). The effects of preferred crystallographic orientation (texture), shape and distribution of grains, local misorientation, type and amount of precipitates as well as the type, size and amount of abrasive carbides, nitrides and oxides on tool wear are investigated in as-built condition and after the standard solutionising and double-aging treatment. The microstructures of workpiece materials and the surfaces of worn tools were examined using different material characterisation techniques, including Scanning Electron Microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and electron backscatter diffraction (EBSD). A dislocation-based approach was used to reveal the cumulative effects of the microstructural characteristics on deformation behaviour and the thermo-mechanical loads on the tools during cutting. The analyses suggest that texture and the extent of material work-hardening prior to the onset of crack formation markedly influence the amount of plastic work and thus heat generation when machining Electron Beam Powder Bed Fusion (EB-PBF) material. The higher heat generation in the cutting zones provokes thermally-induced wear mechanisms like diffusion-dissolution and oxidation. In addition, the larger amount of hard oxide inclusions present in EB-PBF material leads to higher wear by abrasion. In contrast to the prevailing experimental approaches in this field, the present investigation is built on a physics-based framework to understand the fundamental aspects that govern material deformation and heat generation in cutting and, consequently, tool wear mechanisms. This framework can be used for machinability assessment of any alloy manufactured by different additive manufacturing (AM) technologies and for optimising the process-chain, including printing strategies and thermal post-treatments, to improve the machinability of AM alloys by tailoring their microstructure.
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| 35. |
- Mann, James B., et al.
(författare)
-
Large-scale metal strip for power storage and energy conversion applications by machining-based deformation processing
- 2023
-
Ingår i: CIRP Annals. - 0007-8506. ; 72:1, s. 45-48
-
Tidskriftsartikel (refereegranskat)abstract
- Machining-based deformation processing is used to produce metal foil and flat wire (strip) with suitable properties and quality for electrical power and renewable energy applications. In contrast to conventional multistage rolling, the strip is produced in a single-step and with much less process energy. Examples are presented from metal systems of varied workability, and strip product scale in terms of size and production rate. By utilizing the large-strain deformation intrinsic to cutting, bulk strip with ultrafine-grained microstructure, and crystallographic shear-texture favourable for formability, are achieved. Implications for production of commercial strip for electric motor applications and battery electrodes are discussed.
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| 36. |
- Moreno, Maiara, et al.
(författare)
-
Adhesive wear of TiAlN coatings during low speed turning of stainless steel 316L
- 2023
-
Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 524-525
-
Tidskriftsartikel (refereegranskat)abstract
- The wear behavior of TiAlN coatings during turning of stainless steel 316L at low cutting speeds (60–120 m/min) was investigated using scanning electron microscopy. In this speed range, the coatings fail by fracture due to an adhesive wear mechanism. The fracture of the coating is described in detail, including the strong influence of Al-content and cutting speed on the rate of wear. Low Al-content (x ≤ 0.23) coatings showed worse wear resistance than high Al-content (x ≥ 0.53) samples. Less substrate is exposed when the cutting speed is increased, because of reduced adhesive wear. The TiN and Ti0.77Al0.23N coatings are severely worn for all cutting speeds while Ti0.47Al0.53N and Ti0.38Al0.62N remain essentially unaffected at the highest speed. The difference in wear behavior is interpreted as a difference in the fracture toughness of the coatings.
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| 37. |
- Moreno, Maiara, 1993-, et al.
(författare)
-
Strain and phase evolution in TiAlN coatings during high-speed metal cutting : An in operando high-energy x-ray diffraction study
- 2024
-
Ingår i: Acta Materialia. - : Elsevier. - 1359-6454 .- 1873-2453. ; 263
-
Tidskriftsartikel (refereegranskat)abstract
- We report on phase and strain changes in Ti1-xAlxN (0 ≤ x ≤ 0.61) coatings on cutting tools during turning recorded in operando by high-energy x-ray diffractometry. Orthogonal cutting of AISI 4140 steel was performed with cutting speeds of 360–370 m/min. Four positions along the tool rake face were investigated as a function of time in cut. Formation of γ-Fe in the chip reveals that the temperature exceeds 727 °C between the tool edge and the middle of the contact area when the feed rate is 0.06 mm/rev. Spinodal decomposition and formation of wurtzite AlN occurs at the positions of the tool with the highest temperature for the x ≥ 0.48 coatings. The strain evolution in the chip reveals that the mechanical stress is largest closest to the tool edge and that it decreases with time in cut for all analyzed positions on the rake face. The strain evolution in the coating varies between coatings and position on the rake face of the tool and is affected by thermal stress as well as the applied mechanical stress. Amongst others, the strain evolution is influenced by defect annihilation and, for the coatings with highest Al-content (x ≥ 0.48), phase changes.
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| 38. |
- Norrby, Niklas, et al.
(författare)
-
Pressure and temperature effects on the decomposition of arc evaporated Ti0.6Al0.4N coatings during metal cutting
- 2012
-
Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 209, s. 203-207
-
Tidskriftsartikel (refereegranskat)abstract
- The isostructural decomposition of arc evaporated Ti0.6Al0.4N coatings at the elevated temperatures and high stresses occurring during metal cutting have been studied. Comparisons are made with short time (t=10 min) anneals at temperatures typical for steel turning operations. The evolution of the decomposed domain sizes are studied by analytical transmission electron microscopy from samples originating from the rake face. Temperature and force measurements during turning allowed for separation of the effects of the temperature and stresses on domain size evolution. The results show a peak temperature of around 900 °C and a peak normal stress of around 2 GPa during cutting. The overall domain size is larger after cutting compared to the annealed sample at the same temperature. The results suggest that pressures generated during cutting promote coherent isostructural decomposition which is in line with theoretical studies but for considerably higher pressures.
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| 39. |
- Olsson, Mike, et al.
(författare)
-
Study of wear mechanisms of cemented carbide tools during machining of single-phase niobium
- 2020
-
Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 450-451
-
Tidskriftsartikel (refereegranskat)abstract
- In particle accelerator facilities, single-phase niobium is used in superconducting accelerator components. Machining induced surface quality of such components is strongly connected to the functionality of accelerators. In this study, tool wear development and its influence on the surface quality of Nb workpiece have been investigated in longitudinal turning. Uncoated cemented carbide cutting tools were used under finishing conditions (cutting speed vc = 300 m/min and feed f = 0.05 mm/rev) up to the wear criterion of VBmax = 300 μm. A detailed analysis of wear mechanisms of the cutting tool was conducted with help of high resolution electron microscopy (SEM and TEM). Further, the results obtained were correlated with controlled diffusion couples experiments under high pressure – high temperature conditions (2 GPa and 1000 °C). Diffusion of carbon from WC and formation of NbC was found to occur on the niobium – cemented carbide interface. Electron microscopy of the worn tools reports identical mechanisms of diffusion and chemical interaction which lead to rapid flank wear, yet formation of NbC on the rake completely inhibits tool degradation and thus acts as tool protection layer.
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| 40. |
- Persson, Henrik, et al.
(författare)
-
Modelling tool life in high speed machining of AD730
- 2018
-
Ingår i: Procedia Manufacturing. - : Elsevier BV. - 2351-9789. ; 25, s. 316-321, s. 316-321
-
Tidskriftsartikel (refereegranskat)abstract
- AD730® is a new type of nickel-based superalloy, developed by Aubert & Duval, with high temperature properties exceeding conventional superalloys such as Alloy 718. This paper presents the tool life model for this superalloy for the purpose of process optimization and manufacturing cost estimation. The tool life modelling is based on comprehensive machining tests, using the Colding model. The cutting tool material used is CBN 170, a grade specially designed and optimized for machining of nickel-based superalloys.
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| 41. |
- Pilemalm, Robert, 1983-
(författare)
-
TiAlN-based Coatings at High Pressures and Temperatures
- 2014
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- TiAlN and TiAlN-based coatings that are used of relevance as protection of cutting tool inserts used in metal machining have been studied. All coatings were deposited by reactive cathodic arc evaporation using industrial scale deposition systems. The metal content of the coatings was varied by using different combinations of compound cathodes. The as-deposited coatings were temperature annealed at ambient pressure and in some cases also at high pressure. The resulting microstructure was first evaluated through a combination of x-ray diffraction and transmission electron microscopy. In addition, mechanical properties such as hardness by nanoindentation were also reported.TiAlN coatings with two different compositions were deposited on polycrystalline boron nitride substrates and then high pressure high temperature treated in a BELT press at constant 5.35 GPa and at 1050 and 1300 °C for different times.For high pressure high temperature treated TiAlN it has been shown that the decomposition is slower at higher pressure compared to ambeint pressure and that no chemical interaction takes place between TiAlN and polycrystalline cubic boron nitride during the experiments. It is concluded that this film has the potential to protect a polycrystalline cubic boron nitride substrate during metal machining due to a high chemical integrity.TiZrAlN coatings with different predicted driving forces for spinodal decomposition were furthermore annealed at different temperatures. For this material system it has been shown that for Zr-poor compositions the tendency for phase separation between ZrN and AlN is strong at elevated temperatures and that after spinodal decomposition stable TiZrN is formed.
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| 42. |
- Pinchuk, Nataliia, et al.
(författare)
-
INFLUENCE OF DEPOSITION CONDITIONS ON MICROSTRUCTURE AND TEXTURE OF Ti1-XAlXN PVD COATINGS
- 2024
-
Ingår i: NANOCON Conference Proceedings - International Conference on Nanomaterials. - : TANGER Ltd.. - 9788088365150 ; , s. 112-117
-
Konferensbidrag (refereegranskat)abstract
- This study is focused on how the application of pulsed substrate bias during cathodic arc deposition affects the microstructure, texture, grain size and phase composition of (Ti,Al)N coatings. A series of Tix-1AlxN, 0.25≤x≤0.55 coatings were deposited on WC-Co cemented carbide substrates with -30 V, -60 V and -300 V pulsing bias (duty cycle 10 % and a frequence of 1 kHz) under controlled chamber conditions at 4.5 Pa N2-gas and a substrate temperature about 400 °C. The pulsing parameters for the bias (voltage, duty cycle and frequency) were deliberately selected to influence structure, microstructure and composition of the deposited coatings. All Tix-1AlxN coatings had a consistent columnar cubic B1 structure regardless of their chemical composition. Coatings grown at -30 V and -60 V pulsed bias exhibited a pronounced <111> texture attributed to a kinetically driven mechanism influenced by the relative flux of ion species, affecting the surface migration of adatoms during growth. In contrast, the coatings grown with a pulsed bias of -300 V exhibited a reduced <111> texture and the onset of grains with <100> preferred orientation. The transition to the <100> orientation with increased ion energy agrees with the fact that the <111> directions expose the densest array of atoms to the ion beam during growth while the <100> are the most open channeling directions in a B1 structure. The correlation to the preferred with respect to pulsing conditions during growth, correlated to microstructure, grain size and phase composition be further discussed. Surface roughness was highest (Sa≈0.17-0.22 µm) for coating deposited at pulsed bias -30 V.
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| 43. |
- Saketi, Sara, et al.
(författare)
-
Wear of a high cBN content PCBN cutting tool during hard milling of powder metallurgy cold work tool steels
- 2015
-
Ingår i: Wear. - : Elsevier. - 0043-1648 .- 1873-2577. ; 332, s. 752-761
-
Tidskriftsartikel (refereegranskat)abstract
- The wear characteristics of a high cBN content PCBN cutting tool during hard milling of two different hardened cold work tool steels have been evaluated. Post-cutting examination of the worn cutting inserts were performed using high resolution field emission gun scanning electron microscopy, energy dispersive X-ray spectroscopy, Auger electron spectroscopy and optical surface profilometry. Also, the machined work material surfaces and collected chips were characterized in order to evaluate the prevailing wear mechanisms.The results show that both flank and crater wear is controlled by continuous wear due to tribochemical reactions, adhesive wear and mild abrasive wear. Besides, the cutting inserts show a tendency to micro chipping along the cutting edge especially at higher cutting speed. The latter mechanism was also found to be dependent on type of work material. High lateral resolution Auger electron spectroscopy of the crater region show that the worn surface is covered by a thin SixOy rich tribofilm with a thickness of 50-500 nm, the tribofilm being thicker on the binder phase regions. Also, the Co-rich regions of the binder phase seem to be more tribochemically affected by the prevailing contact conditions as compared with the Wrich regions of the binder phase and the cBN phase.
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| 44. |
- Schultheiss, Fredrik, et al.
(författare)
-
Influence of the tool surface micro topography on the tribological characteristics in metal cutting - Part II Theoretical calculations of contact conditions
- 2013
-
Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 298, s. 23-31
-
Tidskriftsartikel (refereegranskat)abstract
- The tribological conditions at the contact between the cutting tool and the chip are of great importance when analyzing the machining process. By knowing the contact conditions on the rake face of the cutting tool the wear on the clearance and rake face may be predicted in terms of size and type of wear. A certain value of the surface stresses is often thought of as leading to a higher wear rate of the cutting tool and thus a shorter tool life. In this article two different methods for experimentally measuring the contact condition on the clearance and rake face of the cutting tool are presented and illustrated with results obtained while turning AISI 4140. Results are also obtained in terms of how the surface roughness value of the cutting tool influences the contact condition. It was found that the tool surface topography may have a significant impact on the tribological performance during machining.
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| 45. |
- Sheikh, Saad, 1987-, et al.
(författare)
-
Fracture toughness of cemented carbides : Testing method andmicrostructural effects
- 2015
-
Ingår i: International journal of refractory metals & hard materials. - : Elsevier. - 0263-4368 .- 2213-3917. ; 49, s. 153-160
-
Tidskriftsartikel (refereegranskat)abstract
- Fracture toughness is one the most important parameters for design applications and performance assessment of WC–Co cemented carbides (hardmetals). Different from hardness, fracture toughness is commonly a property more difficult to evaluate, particularly in brittle materials. A large number of different testing methods have been introduced to evaluate toughness of hardmetals, but in general all of them have either theoretically debatable issues or important experimental difficulties. In this study, three different fracture toughness testing methodologies are investigated: three-point bending on Chevron notched specimen (“reference” baseline), Palmqvist indentation test, and Hertzian indentation method. The work is conducted in several cemented carbide grades with different microstructures, in terms of both WC grain size and Co binder content. It is found that Chevronnotched three-point bending test yields suitable fracture toughness values for a wide range of cemented carbide grades with varying hardness. Concerning indentation methods, the Hertzian one may be particularly recommended, as compared to Palmqvist method, as far as hardness (HV30) drops below 1300. On the other hand, if HV30 is higher than 1300 Palmqvist indentation procedure yields reliable fracture toughness measurements. Experimental findings are finally analyzed and discussed on the basis of two theoretical models proposed in the literature.
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| 46. |
- Sveen, Susanne, et al.
(författare)
-
PCBN hard turning of ball bearing steel : Influence of PVD coating deposition on tool wear and surface finish / surface integrity of machined surface
- 2013
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The wear characteristics of a uncoated and PVD coated low cBN content PCBN cutting tools during hard turning of hardened ball bearing steel have been evaluated. Post-cutting examination of the worn cutting inserts were performed using high resolution field emission gun scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Auger electron spectroscopy (AES) and optical surface profilometry. Also, the machined work material surfaces were characterized in order to evaluate the influence of tool wear on surface finish / surface integrity of machined surface.The PCBN cutting tools evaluated in the present study all display crater wear, flank wear and edge micro chipping. With respect to the observed scatter in the results the influence of PVD coating on crater and flank wear resistance is very small. Besides a gradual wear mainly caused by adhesive and abrasive wear the PVD coatings show a high tendency to spalling. Flank and crater wear of the PCBN material was found to be controlled by both mechanical and tribochemical mechanisms. SEM and EDS analysis of the crater and flank wear regions showed that the worn PCBN surfaces were covered with patches of adhered work material consisting of mainly iron oxide. AES analysis support these results.The machined surfaces show a smooth surface with a Ra-value in the range of 100-200 nm and with a superficial plastic deformation limited to the extreme surface. However, with increasing crater and flank wear in combination with edge chipping the machined surface topography becomes more rough showing Ra-values in the range of 300-400 nm.
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| 47. |
- Weng, Jian, et al.
(författare)
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A comprehensive study on cutting mechanisms and surface integrity of AISI 304 when turning a curved surface
- 2021
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Ingår i: Materials and Manufacturing Processes. - : Informa UK Limited. - 1042-6914 .- 1532-2475. ; 36:11, s. 1285-1298
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Tidskriftsartikel (refereegranskat)abstract
- Most of the studies on cutting mechanisms and surface integrity in turning are investigated with a straight tool path (longitudinal/end face turning) while few contributions have been done in curved surface turning. This work explores the evolutions of cutting force, chip morphology and surface integrity when turning a curved surface, using fillet surface machining of AISI 304 stainless steel. The varying cutting conditions caused by the presented turning are revealed by detailed geometric analysis and employed as indicators for further discussions on cutting force, chip morphology, and machined surface integrity (including surface roughness, microhardness, microstructure, and residual stress). Apart from the difference of cutting force components in tangential, radial, and cutting speed directions along the fillet surface, wider and thinner chips are obtained from end face turning. The measured microhardness, microstructural alternation, and stress condition results comprehensively illustrate a reduction of severe plastic deformation from the outer face to the end face.
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| 48. |
- Weng, Jian, et al.
(författare)
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An analytical method for continuously predicting mechanics and residual stress in fillet surface turning
- 2021
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Ingår i: Journal of Manufacturing Processes. - : Elsevier BV. - 1526-6125. ; 68, s. 1860-1879
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Tidskriftsartikel (refereegranskat)abstract
- A novel and effective approach for determining mechanics and residual stress when turning a component with curved surfaces is presented in this paper. This predictive approach is based on a three-dimensional analytical model to study the distributed mechanics and residual stress caused by vary cutting condition during the machining process. The variation of uncut chip area in this process can be divided into several stages based on different tool-workpiece contact and the discretization of cutting edge is conducted at an arbitrary tool position. The chip flow direction is calculated through the equilibrium of the incremental interaction forces. The cutting force can be determined by integrating the force components along the cutting edge, with each incremental force component obtained based on a fully analytical model. Distributed heat source intensity is considered to model the temperature rise at an arbitrary point in workpiece. The residual stress in curved surface machining is obtained considering the loading-unloading-relaxation procedure at the engagement of cutting edge and machined surface. Finally, Finite Element (FE) modeling and experiments are performed to validate the correctness and robustness of the analytical model proposed in this paper. The results of predicted chip flow direction, cutting force, temperature, and residual stress show good agreement with the simulated and measured results.
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| 49. |
- Zan, Shusong, et al.
(författare)
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Machining SiC fibre reinforced metal matrix composites – How do different matrix materials affect the cutting performance?
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Ingår i: CIRP Annals. - 0007-8506.
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Tidskriftsartikel (refereegranskat)abstract
- SiC fibre reinforced metal matrix composites find widespread application but show major machining difficulties due to significant variations in constituents' properties. In this sense, while the SiC fibre plays significant strengthening effects, the properties mismatch between the brittle fibre and ductile matrix materials becomes important in their machining performance. Through machining tests, SiC fibre reinforced MMCs with Al (soft) and Ti (hard) matrix alloys are evaluated, showing the variation of interaction between inserts and fibres in cutting due to the different matrix properties. This leads to less tool wear but compromised surface integrity in Al-based composite than in Ti-based one.
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| 50. |
- Zhou, Jinming, et al.
(författare)
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Comparative assessment of the surface integrity of AD730® and IN718 superalloys in high-speed turning with a CBN tool
- 2019
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Ingår i: Journal of Manufacturing and Materials Processing. - : MDPI AG. - 2504-4494. ; 3:3
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Tidskriftsartikel (refereegranskat)abstract
- Nickel-based superalloys are typical materials used in components of aeroengines and gas turbine machinery. The strength properties of these alloys at high temperatures are crucial not only to the performance (e.g., power generation efficiency, energy consumption, and greenhouse gas emissions) of aeroengines and industrial gas turbines, but also to machinability during component manufacturing. This study comparatively evaluated the surface integrity of two superalloys, AD730® and Inconel 718 (IN718), during high-speed finishing turning using cubic boron nitride (CBN) tools. IN718 is a conventional superalloy used for the hot section components of aeroengines and industrial gas turbines, while AD730® is a novel superalloy with enhanced high-temperature mechanical properties and good potential as a next-generation superalloy for these components. High-speed turning tests of two superalloys were conducted using a CBN cutting tool and jet stream cooling. The achieved surface integrity of the AD730® and IN718 superalloys was characterized and analyzed to assess the comparability of these alloys.
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