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- Du, Hongying, et al.
(författare)
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Using chip weight distribution as a method to define chip breakability during machining
- 2018
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Ingår i: Proceedings 8th Swedish Production Symposium (SPS). - : Elsevier BV. ; 25, s. 309-315
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Konferensbidrag (refereegranskat)abstract
- Nowadays, the existing evaluation methods of chip breakability in industry are based on subjective visual evaluations of the chip formation during cutting or on a chip chart made after the tests. However, more sensitive methods are needed to provide more in-depth information. Thus, this study proposes a method to better evaluate the chip breakability. Based on a systematically study using the weight distribution measurement method, the results show that a great consistency and reliability to evaluate the chip breakability can be obtained. Overall, it is an objective, available and precise method to be applied in the academic and industrial research. (C) 2018 The Authors. Published by Elsevier B.V.
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- Hanson, Magnus, et al.
(författare)
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On adhesion and metal transfer in sliding contact between TiN and austenitic stainless steel
- 2008
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 264:9-10, s. 781-787
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Tidskriftsartikel (refereegranskat)abstract
- Austenitic stainless steels are known to be very difficult to machine and form. This is due to their tendency to adhere to the tool material, which then initiates galling. In this paper, austenitic stainless steel has been tested against TiN in un-lubricated sliding contact. The interface between TiN and adhered stainless steel was investigated by transmission electron microscopy. An oxide layer, emanating from the stainless steel, was revealed to be present between the tool surface and the adhered stainless steel. It is concluded that the stainless steel oxide plays a major role for the sticky behavior of this material. To further investigate this phenomenon, austenitic stainless steel samples were also pre-oxidised before testing to examine if the oxide thickness and composition are important for the adhesion tendency. The test showed that the sample oxidised at 800 °C had less tendency to adhere than those oxidised at lower temperatures. The explanation is either its higher thickness, or its high content of Cr-oxide in its surface. The surface of the oxides formed at lower temperatures consists mainly of iron oxide.
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- Stavlid, Nils, 1975-
(författare)
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On the Formation of Low-Friction Tribofilms in Me-DLC – Steel Sliding Contacts
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The present thesis thoroughly treats a special friction reduction phenomenon that may appear in boundary lubricated tribological contacts, of the type encountered in numerous mechanical components made of steel. The phenomenon involves the formation of a special type of tribofilm that offers very low coefficients of friction. Typically the friction level becomes halved when the film is formed, compared to when it is not formed. Since boundary lubricated mechanical components are so common in all sorts of machinery, the technical and economical potential of this phenomenon is gigantic.The tribofilm is produced on the steel surface, resulting in friction coefficient reduction from typically 0.08–0.1 to 0.04–0.06. The tribofilm is formed from the metal in the carbon coating and sulfur in the oil additive. The main film studied was WS2, which is a well-known low-friction material. It includes easy shearing atomic planes, in the same fashion as the solid lubricants MoS2 and graphite. Virtually no carbon is present in the tribofilm, despite carbon being the main constituent of both the coating and the additive. No films form on the Me-DLC coated part.It was also found that WSi2-particles could result in the formation of WS2-containing tribofilms. It was concluded that they, just as the W-DLC film, were sufficiently weak to mill down to very small particles, and chemically reactive in the prevailing tribological conditions. However, WC particles were too stable, both mechanically and chemically, to result in any film formation.The chemical driving forces for formation of the tribofilms were analyzed using EkviCalc, a commercial software for thermodynamical calculations based on minimization of Gibbs free energy for a system as a function of temperature and pressure. The simulations indeed confirmed that both WS2 and MoS2 should be expected to be stable compounds, coexisting with FeS, in the studied environment. As a spin-off result, the thermodynamical calculations indicated that coatings of the Cr-C type should impose very little tribochemical wear of the uncoated steel surface, and even reduce the forma-tion of FeS (the “traditional” tribofilm) on the steel surface in S-containing environments. As a final spin-off, the thermodynamical calculations indicate that the Ti-C coating should be very resistant to tribochemical wear in the S-containing environment.
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