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| 2. |
- Saketi, Sara, et al.
(författare)
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Wear of a high cBN content PCBN cutting tool during hard milling of powder metallurgy cold work tool steels
- 2015
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Ingår i: Wear. - : Elsevier. - 0043-1648 .- 1873-2577. ; 332, s. 752-761
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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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| 4. |
- Sveen, Susanne, et al.
(författare)
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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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| 5. |
- Sveen, Susanne, et al.
(författare)
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Scratch adhesion characteristics of PVD TiAlN deposited on high speed steel, cemented carbide and PCBN substrates
- 2013
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Ingår i: Wear. - : Elsevier. - 0043-1648 .- 1873-2577. ; 308:1-2, s. 133-141
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Tidskriftsartikel (refereegranskat)abstract
- Modern tool materials, ranging from powder metallurgical high speed steel to super hard materials such as polycrystalline cubic boron nitride and diamond, are used as cutting tools in the metal cutting industry. In order to further improve the cutting performance, these tools are frequently coated by thin, hard PVD coatings such as TiN, TiAlN, AlCrO3, etc. In order to develop and design new PVD coatings it is important to characterize the mechanical properties of the coatings and understand the coating/substrate deformation mechanisms in a tribological contact, e.g. metal cutting. For example, it is important to be aware that the mechanical properties of the substrate (tool material) have a significant impact on the practical coating adhesion and the coating failure mechanisms.In the present study scratch testing has been used in order to evaluate to increase the understanding of the mechanical response and potential coating failure modes of cathodic arc evaporated TiAlN deposited on high speed steel, cemented carbide and polycrystalline cubic boron nitride. Post-test characterization of the scratched samples using optical profilometry, scanning electron microscopy and energy dispersive X-ray spectroscopy were performed and the cohesive and adhesive surface failure mechanisms are described and related to the substrate material properties. The results clearly show that, although all substrate materials can be regarded as hard, they result in completely different coating failure mechanisms at the normal load corresponding to substrate exposure. Also, coating failure resulting in substrate exposure does not necessarily correspond to interfacial cracking resulting in adhesive fracture along the coating-substrate interface.
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| 6. |
- Sveen, Susanne
(författare)
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Wear of coated and uncoated PCBN cutting tool used in turning and milling
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This licentiate thesis has the main focus on evaluation of the wear of coated and uncoated polycrystalline cubic boron nitride cutting tool used in cutting operations against hardened steel. And to exam the surface finish and integrity of the work material used. Harder work material, higher cutting speed and cost reductions result in the development of harder and more wear resistance cutting tools. Although PCBN cutting tools have been used in over 30 years, little work have been done on PVD coated PCBN cutting tools. Therefore hard turning and hard milling experiments with PVD coated and uncoated cutting tools have been performed and evaluated. The coatings used in the present study are TiSiN and TiAlN. The wear scar and surface integrity have been examined with help of several different characterization techniques, for example scanning electron microscopy and Auger electron spectroscopy. The results showed that the PCBN cutting tools used displayed crater wear, flank wear and edge micro chipping. While the influence of the coating on the crater and flank wear was very small and the coating showed a high tendency to spalling. Scratch testing of coated PCBN showed that, the TiAlN coating resulted in major adhesive fractures. This displays the importance of understanding the effect of different types of lapping/grinding processes in the pre-treatment of hard and super hard substrate materials and the amount and type of damage that they can create. For the cutting tools used in turning, patches of a adhered layer, mainly consisting of FexOy were shown at both the crater and flank. And for the cutting tools used in milling a tribofilm consisting of SixOy covered the crater. A combination of tribochemical reactions, adhesive wear and mild abrasive wear is believed to control the flank and crater wear of the PCBN cutting tools. On a microscopic scale the difference phases of the PCBN cutting tool used in turning showed different wear characteristics. The machined surface of the work material showed a smooth surface with a Ra-value in the range of 100-200 nm for the turned surface and 100-150 nm for the milled surface. With increasing crater and flank wear in combination with edge chipping the machined surface becomes rougher and showed a higher Ra-value. For the cutting tools used in milling the tendency to micro edge chipping was significant higher when milling the tools steels showing a higher hard phase content and a lower heat conductivity resulting in higher mechanical and thermal stresses at the cutting edge.
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