| 1. |
- 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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| 2. |
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| 3. |
- Nyberg, Harald, et al.
(författare)
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Design of low-friction PVD coating systems with enhanced running-in performance - carbon overcoats on TaC/aC coatings
- 2013
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Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 222, s. 48-54
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Tidskriftsartikel (refereegranskat)abstract
- The widespread use of low friction PVD coatings on machine elements is limited by the high costs associated with fulfilling the demands on the surface quality of both the supporting substrate and the counter surface. In this work, an attempt is made at lowering these demands, by adding a sacrificial carbon overcoat to a TaC/aC low friction coating. Both coatings were deposited by planar magnetron DC sputtering, as separate steps in a single PVD-process. Coatings were deposited on substrates of two different surface roughnesses, in order to test the ability of this coating system to function on rougher substrates. Reciprocating ball on disc tests was performed, using balls with two different surface roughnesses. The worn surfaces were investigated using 3-D profilometry and SEM. The ability of the different overcoats to initially reduce the roughness of both the coated surface and the counter surface and to produce stable, low-friction conditions was examined for the different initial roughnesses. The implications for design of efficient run-in coatings for various systems are discussed.
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| 4. |
- Nyberg, Harald, 1985-, et al.
(författare)
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Design of low-friction PVD coating systems with enhanced running-in performance - carbon overcoats on TaC/aC coatings
- 2012
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Ingår i: Nordtrib 2012, 15th Nordic Symposium on Tribology.
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Konferensbidrag (refereegranskat)abstract
- The widespread use of low friction PVD coatings on machine elements is limited by the high costs associated with fulfilling the demands on the surface quality of both the supporting substrate and the counter surface. In this work, an attempt is made at lowering these demands, by adding a sacrificial carbon overcoat to a TaC/aC low friction coating. Both coatings were deposited by planar magnetron DC sputtering, as separate steps in a single PVD-process. Coatings were deposited on substrates of two different surface roughnesses, in order to test the ability of this coating system to function on rougher substrates. Reciprocating ball on disc tests were performed, using balls with two different surface roughnesses. The worn surfaces were investigated using 3-D profilometry and SEM. The ability of the different overcoats to initially reduce the roughness of both the coated surface and the counter surface and to produce stable, low-friction conditions was examined for the different initial roughnesses. The implications for design of efficient run-in coatings for various systems are discussed.
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| 5. |
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| 6. |
- Nyberg, Harald, 1985-, et al.
(författare)
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On the influence from micro topography on the structure and growth of low friction amorphous carbon PVD coatings
- 2010
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Ingår i: Twelfth International Conference on Plasma Surface Engineering (PSE 2010), September 13-17, 2010, Garmisch-Partenkirchen.
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Konferensbidrag (refereegranskat)abstract
- The interest in metal carbide doped amorphous carbon coatings produced by physical vapour deposition (PVD) for use on heavily stressed machine elements is currently increasing, mainly due to their ability to achieve low friction and reduced wear of the counter surface. The tribological properties of these types of coatings have however been found to vary strongly between seemingly similar coatings. A potential source of these differences could be the micro topography of the coated surfaces. Argon ion etch cleaning of the substrates is a common process step in the production of PVD coatings and is usually performed as the final cleaning step before coating deposition. For some materials, the etching process may result in a roughening of the substrate surface, due to differences in the etch rates of the different parts of the material. In high speed steels, carbides typically etch slower than the metallic phase, resulting in a surface covered by protruding carbides. In the current study, it was examined how varying amounts of argon ion etching of highly polished high speed steel substrates prior to coating influences the micro topography of the substrates and the final coatings. Tantalum carbide doped amorphous carbon coatings (TaC:C) were produced by co-sputtering of carbon and tantalum, in an argon atmosphere. The impact of the substrate micro topography on the growth and structure of the coatings was studied, using high resolution scanning electron microscopy (SEM) of superficial coating cross sections produced with a focused ion beam (FIB). Special attention was paid to coating growth in the immediate vicinity of protruding carbides, as well as to the structure of the coating in these regions.
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| 7. |
- Olofsson, Johanna, 1981-, et al.
(författare)
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On the influence from micro topography of PVD coatings on friction behaviour, material transfer and tribofilm formation
- 2011
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Ingår i: Wear. - : Elsevier. - 0043-1648 .- 1873-2577. ; 271:9-10, s. 204-2057
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Konferensbidrag (refereegranskat)abstract
- PVD coatings based on amorphous carbon with metal-carbides are currently gaining a high interest for use on machine elements due to their potential to give low friction and low wear of the counter surface. However, the performance varies significantly between the various types of such coatings and the causes of this are not clear. One factor is the micro topography of the coating surface. This topography may influence the friction in many ways; by changing the state of lubrication, by causing scratching of the counter surface, by modifying the topography of the counter surface the material transfer, the tribofilm formation, etc.TaC/a-C coatings, produced by co-sputtering of carbon and tantalum in an argon atmosphere, were deposited on high speed steel substrates exposed to varying degrees of etching to produce a range of surface roughnesses. Ball-on-disc experiments were used to evaluate the tribological properties of the coatings in dry condition against a ball bearing steel ball. The surfaces were analysed using various advanced techniques, including, SEM, XPS, Raman, EDS and AFM, all both prior to and after the testing.It was shown that the resulting surface topography of the coating is affected even by very small protrusions on the substrate. The coefficient of friction decreased during use to a stable level, due to a complex process including tribofilm build-up on the sliding ball. Surfaces with lower protrusions exhibited a faster friction decrease, i.e. a faster running in.
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