| 1. |
- Bara, Özlem, et al.
(författare)
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Adhesion and tribological properties of TiTaBN coatings with a graded interlayer deposited by pulsed DC biased and continuous dc biased magnetron sputtering
- 2015
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Ingår i: Journal of Adhesion Science and Technology. - : Informa UK Limited. - 0169-4243 .- 1568-5616. ; 29:18, s. 2006-2019
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Tidskriftsartikel (refereegranskat)abstract
- The properties of TiBN-based coatings are significantly affected by adding alloying elements and coating parameters. Therefore, in this study, TiTaBN coatings with graded interlayer (CWGIL) were deposited on D2 steel substrates by pulsed DC biased (PDCB) and continuously DC biased (CDCB) closed field unbalanced magnetron sputtering (CFUBMS). The structural, mechanical, adhesion and tribological properties of the coatings were analysed with EDS, SEM, XRD, microhardness, scratch testing and a pin-on-disc tribo-tester (under various atmospheric conditions). TiTaBN CWGIL deposited by PDCB magnetron sputtering (MS) had a very dense microstructure, high hardness and a high critical load value. TiTaBN CWGIL deposited by PDCB MS had a lower friction coefficient, the wear rate and the penetration depth in all atmospheric conditions. In conclusion, the application of a PDCB substrate instead of a CDCB one dramatically increases the performance of CFUBMS-deposited TiTaBN coatings.
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| 2. |
- Courbon, Cedric, et al.
(författare)
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Adhesion tendency of PVD TiAlN coatings at elevated temperatures during reciprocating sliding against carbon steel
- 2015
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 330-331, s. 209-222
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Tidskriftsartikel (refereegranskat)abstract
- This work focussed on assessing the contact conditions driving the adhesion tendency of PVD TiAlN coated cemented carbide during reciprocating sliding against a normalized AISI 4137 carbon steel. A special emphasis is given to the surface topography of the coating. Results are analysed in terms of friction and material transfer over a large range of temperatures (up to 800 °C) and contact pressures. The post-test surface analysis of the specimens is conducted in order to understand the tribological behaviour and elucidate the formation mechanisms of transfer layers. A numerical model is developed to assess the amount of heat effectively transmitted into the first bodies and the temperature of the surfaces in contact.Whereas temperatures close to 400 °C ensure the formation of a stable tribofilm reducing friction, the highest temperatures lead to unstable frictional behaviour. Coating surface topography has been seen to be a major parameter driving material transfer during the first stages of the contact and the formation of a transfer layer. Thin and homogeneous layers are almost instantaneously formed with a polished surface whereas some time is required with a rougher one to form a film. A large amount of the frictional power is dissipated into these layers and high temperatures can be reached at the surface due to frictional heating. Contact pressure is found to be a parameter promoting transfer and oxidation
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| 3. |
- Decrozant-Triquenaux, Justine, 1994-, et al.
(författare)
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Effect of Surface Engineered Tool Steels on Frition and Wear During Sliding Against Aluminium at High Temperatures
- 2018
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Konferensbidrag (refereegranskat)abstract
- Usage of high-strength aluminium alloys is increasing for automotive applications due to high strength-to-weight ratios. Limited formability at room temperature requires hot forming for production of complex geometries. The occurrence of severe adhesion and material transfer negatively affects process economy and there is a need for effective solutions to overcome these issues. This work is focussed on the high-temperature tribological behaviour of Al6016 alloy and uncoated/PVD coated tool steels. Studies were conducted under dry and lubricated conditions using a high-temperature reciprocating tribometer. High friction in dry sliding for uncoated and coated tool steels was observed. Hexagonal boron nitride lubricant was not effective in reducing friction. DLC coating with a polymer lubricant resulted in the lowest friction and minimised material transfer.
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| 4. |
- Decrozant-Triquenaux, Justine, 1994-, et al.
(författare)
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Tribological Behaviour of PVD Coated Tool Steels in Hot Forming of Aluminium Alloys
- 2019
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Ingår i: Hot sheet metal forming of high-performance steel. ; , s. 365-372
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Konferensbidrag (refereegranskat)abstract
- Aluminium alloys are commonly used as light-weight materials in the automotive industry. This non-ferrous family of metal alloys offers high versatility of properties and designs. In order to reduce weight and improve safety, grades with high strength-to-weight ratio, such as the 6XXX and 7XXX alloy series, are increasingly implemented in vehicles. These alloys, however, exhibit low formability and experience considerable springback when formed at low temperatures, and thus have to be formed at elevated temperatures. Severe adhesion and galling are known to be critical tribological challenges in hot forming of aluminium. During the forming operation, adhesion and transfer of aluminium onto the die surface take place. This phenomenon has a detrimental effect on the surface properties, geometrical tolerances of the formed parts and maintenance of the dies. The influence of surface engineering as well as lubricant composition on adhesion and galling has not been sufficiently investigated. Diamond-like-Carbon and Chromium Nitride PVD coatings applied on the tool steel have shown promising results for reducing aluminium transfer at high-temperatures, especially in the presence of a lubricant. However, the interaction between lubricants and PVD coatings during hot forming of aluminium alloys is not yet fully understood. The present study thus aims at characterising the high temperature tribological behaviour of selected PVD coatings and a lubricant during sliding against an aluminium alloy. The objectives are to select promising lubricant-coating combinations for the given application and to study their tribological response in a high-temperature reciprocating friction and wear tester. The tests were carried out at 300°C, under dry and lubricated conditions, in order to study the friction and wear performance. Uncoated tool steel reference tests were performed under dry and lubricated conditions and lubricated tests using DLC, CrN, CrTiN and CrAlN coated tool steel were performed and compared to the reference results. The initial and worn surfaces were analysed with white light 3D optical interferometry, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) with a view to understand the wear mechanisms.
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| 5. |
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| 6. |
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| 7. |
- Deng, Liang, 1986-, et al.
(författare)
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Development of a Tribological Test Programme Based on Press Hardening Simulations
- 2017
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Ingår i: Tribology letters. - : Springer. - 1023-8883 .- 1573-2711. ; 65:2
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Tidskriftsartikel (refereegranskat)abstract
- Press hardening is widely utilized to form ultra-high-strength steels characterized by a high strength-to-weight ratio for automotive components. Press hardening processes include heating boron–manganese steels to austenite phase, forming the steels at a high temperature, and cooling the formed blanks until the martensite phase is reached . However, press hardening processes lead to severe contact conditions between the blank and the tools including contact pressure, relative sliding, and high temperatures, which result in tool wear and increased maintenance cost. The contact conditions that occur in the stamping tool are difficult to study on site. Additionally, simplified tests, such as pin on disc and ball on disc, are insufficient to reproduce press hardening conditions in laboratory environments . The aim of this study includes developing a tribological test with press hardening conditions in which tool steel pins continuously slide on fresh and hot boron–manganese steel strips. The test programme mimics press hardening conditions with respect to sliding distance, sliding velocity, contact pressure, and surface temperature that were studied based on finite element (FE) simulations of a press hardening experiment. Furthermore, a FE simulation of the tribological test is established and it provides contact temperature in the pin tip with a high accuracy. A tribological test is used to study friction and mass loss with variational pressures and velocities that represented typically variational contact conditions in the press hardening. The tribological test is also used to obtain correlations between the tribological behaviours and process parameters in press hardening including pressure and sliding velocity.
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| 8. |
- Deng, Liang, 1986-, et al.
(författare)
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Experimental Evaluation of Galling Under Press Hardening Conditions
- 2018
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Ingår i: Tribology letters. - : Springer. - 1023-8883 .- 1573-2711. ; 66:3
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Tidskriftsartikel (refereegranskat)abstract
- Severe adhesion, also referred to as galling, is a critical problem in press hardening, especially in stamping tools used for hot forming of Al–Si-coated ultra-high strength steel. Galling is known to develop rapidly on the tool surface and it negatively affects the quality of the formed products. Earlier research on this topic has focused on the galling initiation. However, studies on the galling development during extended sliding and the corresponding quantitative measurement still lack depth. In the present study, a tribological test is established to study the galling development under press hardening conditions. The tribological test set-up aims to simulate extended sliding between the Al–Si-coated boron steels and the tool die material. The contact conditions in the interface are studied by a numerical model of the tribological test. The friction coefficients and material transfer are discussed taking into account the variation of the different test conditions. Using the results from the tribological tests, the galling simulation is performed in the numerical model. A geometry-updated sample based on the galling (transferred material build-up) height is simulated and the consequent pressure fluctuation is obtained in the numerical model. This contributes to the explanation of the severe transferred material accumulation during the test.
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| 9. |
- Deng, Liang, 1986-, et al.
(författare)
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Numerical investigation of galling in a press hardening experiment with AlSi-coated workpieces
- 2019
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Ingår i: Engineering Failure Analysis. - : Elsevier. - 1350-6307 .- 1873-1961. ; 99, s. 85-96
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Tidskriftsartikel (refereegranskat)abstract
- Press hardened steels are commonly used as a lightweight choice for manufacturing car components because of the high ratio of strength to weight. The use of ultra-high-strength steels for the design of lightweight vehicles contributes to the reduction of emissions of carbon dioxide while maintaining passenger safety. Stamping tools used in press hardening processes suffer harsh contact conditionsin terms of dramatic temperature changes, cyclic loadings, and complex interactions between coatings and oxidation. In mass production, tool wear is an inevitable problem that increases maintenance costs. Severe adhesive wear, also called galling, substantially occurs in the stamping tool used against Al—Si-coated workpieces. The galling that takes place during press hardening not only degrades the production quality but also shortens the service life of the tool. In order to properly arrange tool maintenance and minimize galling through adjusting process parameters, engineers need to know when and where galling occurs, based on modelling of the galling in press hardening simulations. In order to implement a galling simulation for press hardening, a modified Archard wear model is employed in the present study, which is a contact-mechanics-based model. The specific wear rate in the model is calibrated by the quantitative galling measurements of a high-temperature tribometer test. The tribological test is designed to mimic the press hardening conditions, where the correlations between galling and process parameters such as temperature, pressure, and sliding distance are outlined. The galling simulation is implemented in a full-scale press hardening experiment, and the predicted galling is validated in terms of severe galling positions and galling profiles. The galling profile evolution is correlated to variations in the contact conditions. Uncertainties in the numerical model, such as the choice of penalty scaling factor and friction coefficient, are analysed with a parameter study and discussed. This study demonstrates finite element (FE) simulations involving galling prediction in press hardening so as to improve product development and production efficiency.
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| 10. |
- Deng, Liang, et al.
(författare)
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Numerical study of contact conditions in press hardening for tool wear simulation
- 2017
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Ingår i: International Journal of Material Forming. - : Springer. - 1960-6206 .- 1960-6214. ; 10:5, s. 717-727
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Tidskriftsartikel (refereegranskat)abstract
- In the press hardening industry, industrial and academic efforts are being directed toward predicting tool wear to realize an economical manufacturing process. Tool wear in press hardening is a tribological response to contact conditions such as pressure and sliding motion. However, these contact conditions are difficult to measure in-situ. Furthermore, press hardening involves high temperatures, and this increases the complexity of the tribo system. The present work investigated the contact conditions of press hardening with a commercial FE code (LS-DYNA) as a base for tool wear simulation. A press hardening experiment was established in industrial environments and evaluated through FE simulations. The numerical model was set up so as to approximate the manufacturing conditions as closely as possible, and the sensitivity with respect to the friction coefficients was examined. The influence of numerical factors such as the penalty value and mesh size on the contact conditions is discussed. The implementation of a modified Archard’s wear model in the FE simulation proved the possibility of tool wear simulation in press hardening. Finally, a comparison between the tool wear simulation and the measured wear depth is presented.
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