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- Gerth, Julia, et al.
(författare)
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Adhesion phenomena in the secondary shear zone in turning of austenitic stainless steel and carbon steel
- 2014
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Ingår i: Journal of Materials Processing Technology. - : Elsevier BV. - 0924-0136 .- 1873-4774. ; 214:8, s. 1467-1481
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Tidskriftsartikel (refereegranskat)abstract
- This paper aims to increase the understanding of the adhesion between chip and tool rake face by studying the initial material transfer to the tool during orthogonal machining at 150 m/min. Two types of work material were tested, an austenitic stainless steel, 316L, and a carbon steel, UHB 11. The tools used were cemented carbide inserts coated with hard ceramic coatings. Two different CVD coatings, TiN and Al2O3, produced with two different surface roughnesses, polished and rough, were tested. The influences of both tool surface topography and chemistry on the adhesion phenomena in the secondary shear zone were thus evaluated. Extensive surface analyses of the inserts after cutting were made using techniques such as Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-ray Photoelectron Spectroscopy (XPS), and Transmission Electron Microscopy (TEM). As expected, cutting in the stainless steel resulted in a higher amount of adhered material, compared to cutting in the carbon steel. Remnants of built-up layers were found on the surfaces of the 316L chips but not on the UHB 11 chips. Moreover, it was shown that for both materials the tool roughness had a profound effect, with the rougher surfaces comprising much higher amounts of adhered material than the polished ones. Non-metallic inclusions from both types of workpiece steels accumulate in the high temperature area on the inserts. The general tendency was that higher amounts of transferred material were found on the TiN coating than on the Al2O3 coating after cutting.
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| 3. |
- Gerth, Julia, et al.
(författare)
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Evaluation of an intermittent sliding test for reproducing work material transfer in milling operations
- 2012
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Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 52, s. 153-160
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Tidskriftsartikel (refereegranskat)abstract
- TiN coated HSS test cylinders from an intermittent sliding test were compared with TiN coated HSS milling inserts from a single insert milling test. A 20NiCrMo2 case hardening steel was used as counter material and work material in the two tests. HSS test cylinders, coated with AlCrN, TiAlN and Al2O3, were also tested in the intermittent sliding test and evaluated with regard to material adhesion. Two distinctly different tribofilms were formed on test cylinders as well as on cutting inserts. One consisting of Mn, Si, Al and O and one consisting of Fe, Mn, Cr, Si and O. The transferred material was similar in appearance and composition, both when comparing the two test methods and when comparing the different tool coatings.
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| 4. |
- Heinrichs, Jannica, et al.
(författare)
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Exploring the tribochemical wear and material transfer caused by Cu15Zn alloys on shearing tools
- 2024
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Ingår i: Wear. - : Elsevier. - 0043-1648 .- 1873-2577. ; 542
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Tidskriftsartikel (refereegranskat)abstract
- Cemented carbide tools are extensively used in the zipper industry, including shearing of a pre-formed Cu15Zn wire into individual zipper elements. Although the work material is significantly softer than the tool, wear is the life limiting factor for the tools and is considered to be of tribochemical nature. So far it has not been explained, however, it is known that the wear rate of uncoated, as well as CrC and CrN coated, cemented carbide increases dramatically when Zn is omitted from the Cu alloy. In this paper, worn tool surfaces, including any transferred material, were studied to investigate the tribochemical wear mechanism in detail. Material transfer occurred onto all tool surfaces. Cu and Zn were separated on the sub-micron scale, and preferential transfer of one of the constituents was observed. This is reflected in the outermost surface of the sheared element, which shows a homogeneous composition elsewhere. Oxidation was observed of all tool surfaces, which indicates elements of oxidative wear. Further, any Zn transferred to the tool surfaces was oxidized. Thus, it is suggested that the presence of Zn reduces the oxygen available and consequently reduces the oxidation rate of the tool surfaces, leading to the protective effect previously observed. © 2024 The Authors
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| 5. |
- Heinrichs, Jannica, et al.
(författare)
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Influence from surface roughness on steel transfer to PVD tool coatings in continuous and intermittent sliding contacts
- 2012
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Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 56, s. 9-18
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Tidskriftsartikel (refereegranskat)abstract
- A sliding test is used in order to evaluate the influence of tool surface roughness on the material transfer in intermittent and continuous sliding of PVD coated HSS against case hardening steel (20NiCrMo2). Two cutting tool coatings, TiN and AlCrN, and three different surface roughnesses are tested. For polished surfaces the same types of material transfer are obtained irrespective of sliding mode and coating type. If the surfaces are too rough, the tribofilms do not grow thick enough to separate the surfaces and the work material is abrasively worn in both sliding modes. With increased sliding distance, cracking of the TiN coating occurs while the AlCrN coating remains intact.
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| 6. |
- Heinrichs, Jannica, et al.
(författare)
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Influence of sliding speed on modes of material transfer as steel slides against PVD tool coatings
- 2013
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Ingår i: Tribology International. - : Elsevier. - 0301-679X .- 1879-2464. ; 58, s. 55-64
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Tidskriftsartikel (refereegranskat)abstract
- An intermittent sliding test was used in order to study the formation and build- up of tribofilms during intermittent sliding of PVD coated HSS against case hardening steel (20NiCrMo2). Two cutting tool coatings were tested, TiN and AlCrN, and the influence of sliding speed was evaluated. With moderate speed, two tribofilms were formed separately, one consisting of Mn, Si, Al and O on an intermediate layer of Fe and one consisting of Fe, Mn, Cr and O on an intermediate layer of Cr and Mn. At low sliding speeds an uneven transfer of steel occured while high sliding speeds resulted in thermal softening of the substrate leading to coating failure. AlCrN provided better substrate protection at high speeds than TiN did.
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| 7. |
- Heinrichs, Jannica, 1982-
(författare)
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On Transfer of Work Material to Tools
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bulk forming and cutting are widely used to shape metals in industrial production. Bulk forming is characterized by large strains, extensive plastic deformation and large surface expansions. Cutting is characterized by high speeds, high pressures and high temperatures. The prevailing conditions during these processes lead to transfer of work material to tools. In bulk forming this is a significant problem. The transferred work material is hardened and becomes harder than the work material, causing galling. This leads to high friction and high forming forces, bad surface finish of the formed products and significant difficulties to produce complicated geometries. In cutting, transfer of work material can be desired for protection of the tool surface. However, the transfer film has to be of the correct type to provide a stable and predictive behaviour during operation.In this thesis the influence from tool material and surface treatment on work material transfer has been studied for both applications, with the use of simplified laboratory test methods followed by extensive surface studies. Both the tendency to, appearance of and chemical composition of work material transfer is evaluated. The results are compared with real industrial examples, to ensure that the correct mechanisms are mimicked.In forming, the problems arise when poor lubrication prevails, due to high forming forces or large surface expansions. The transfer of work material can then be avoided with the use of a galling resistant coating, offering low adhesion. However, the coating has to be as smooth as possible, to avoid activation of the work material and subsequent transfer.In cutting, the desired transfer film can be obtained by choosing the correct cutting parameters. The geometry and material of the fabricated component is often predetermined, setting the general cutting conditions, but the cutting speed influences the formation of the transfer film. Too low speed or too high speed leads to an unstable cutting process and poor surface finish of the piece. The speed intervals for each mechanism are partly determined by the tool material and thus by the tool coating.
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| 10. |
- Heinrichs, Jannica, 1982-, et al.
(författare)
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Wear mechanisms of WC-Co cemented carbide tools and PVD coated tools used for shearing Cu-alloy wire in zipper production
- 2019
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 420, s. 96-107
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Tidskriftsartikel (refereegranskat)abstract
- To form the individual elements, that together form a zipper, a pre-formed Cu-alloy wire is sheared using cemented carbide tools. The wear caused by the relatively soft copper alloy on the much harder tool is generally quite slow. However, millions of elements are to be sheared so eventually the wear becomes unacceptable and the tool needs to be exchanged. To improve product quality, as well as minimize down time and material consumption, the tool life needs to be prolonged. To achieve this the wear process needs to be better understood. Uncoated tools used for an increasing number of shearing events have been studied in detail using high resolution SEM and EDS, to map the propagating wear and get an insight into the wear mechanisms. Transfer of material from the Cu-alloy to the tool occurs and the wear is highly concentrated to specific areas. This wear occurs on a very fine scale, limited to within individual WC grains at each event. Tools coated with PVD CrC and PVD CrN have been studied for comparison with the uncoated cemented carbide. Both coatings successfully protect the cemented carbide tool from wear, however occasional flaking occurs and then the cemented carbide becomes exposed and subsequently worn. The differences in performance and wear mechanisms between the uncoated and coated tools are discussed, with focus on the capability of the coatings to prolong the tool life.
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