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Saketi, S., Östby, J., Bexell, U. & Olsson, M. (2019). A Methodology to Systematically Investigate the Diffusion Degradation of Cemented Carbide during Machining of a Titanium Alloy. Materials, 12(14), 1-17, Article ID 2271.
Open this publication in new window or tab >>A Methodology to Systematically Investigate the Diffusion Degradation of Cemented Carbide during Machining of a Titanium Alloy
2019 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 14, p. 1-17, article id 2271Article in journal (Refereed) Published
Abstract [en]

Using Ti6Al4V as a work material, a methodology to systematically investigate the diffusion degradation of cemented carbide during machining is proposed. The methodology includes surface characterization of as-tested worn inserts, wet etched worn inserts, metallographic cross-sectioned worn inserts as well as the back-side of the produced chips. Characterization techniques used include scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Auger electron spectroscopy (AES) and time of flight secondary ion mass spectroscopy (ToF-SIMS). The results show that the characterization of wet etched worn inserts gives quick and useful information regarding the diffusion degradation of cemented carbide, in the present work the formation of a fine crystalline W layer (carbon depleted WC layer) at the tool-work material interface. The present study also illuminates the potential of AES analysis when it comes to analyzing the degradation of cemented carbide in contact with the work material during machining. The high surface sensitivity in combination with high lateral resolution makes it possible to analyze the worn cemented carbide surface on a sub-mu m level. Especially AES sputter depth profiling, resulting in detailed information of variations in chemical composition across interfaces, is a powerful tool when it comes to understanding diffusion wear. Finally, the present work illustrates the importance of analyzing not only the worn tool but also the produced chips. An accurate characterization of the back-side of the chips will give important information regarding the wear mechanisms taking place at the tool rake face chip interface. Surface analysis techniques such as AES and ToF-SIMS are well suited for this type of surface characterization.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
turning, Ti6Al4V, wear, tool, chip, SEM, AES, ToF-SIMS
National Category
Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:uu:diva-393637 (URN)10.3390/ma12142271 (DOI)000480454300059 ()31311114 (PubMedID)
Available from: 2019-09-25 Created: 2019-09-25 Last updated: 2019-10-24Bibliographically approved
Saketi, S., Odelros, S., Ostby, J. & Olsson, M. (2019). Experimental Study of Wear Mechanisms of Cemented Carbide in the Turning of Ti6Al4V. Materials, 12(17), Article ID 2822.
Open this publication in new window or tab >>Experimental Study of Wear Mechanisms of Cemented Carbide in the Turning of Ti6Al4V
2019 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 17, article id 2822Article in journal (Refereed) Published
Abstract [en]

Titanium and titanium alloys such as Ti-6Al-4V are generally considered as difficult-to-machine materials. This is mainly due to their high chemical reactivity, poor thermal conductivity, and high strength, which is maintained at elevated temperatures. As a result, the cutting tool is exposed to rather extreme contact conditions resulting in plastic deformation and wear. In the present work, the mechanisms behind the crater and flank wear of uncoated cemented carbide inserts in the turning of Ti6Al4V are characterized using high-resolution scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and high-resolution Auger electron spectroscopy (AES).The results show that, for combinations of low cutting speeds and feeds, crater and flank wear were found to be controlled by an attrition wear mechanism, while for combinations of medium to high cutting speeds and feeds, a diffusion wear mechanism was found to control the wear. For the latter combinations, high-resolution SEM and AES analysis reveal the formation of an approximately 100 nm thick carbon-depleted tungsten carbide (WC)-layer at the cemented carbide/Ti6Al4V interface due to the diffusion of carbon into the adhered build-up layers of work material on the rake and flank surfaces.

Keywords
turning, cemented carbide, Ti6Al4V, attrition wear, diffusion wear, SEM, EDS
National Category
Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:uu:diva-396546 (URN)10.3390/ma12172822 (DOI)000488880300175 ()31480695 (PubMedID)
Available from: 2019-11-07 Created: 2019-11-07 Last updated: 2019-11-07Bibliographically approved
Saketi, S. (2019). Investigation of Topography, Adhesion and Diffusion Wear in Sliding Contacts during Steel and Titanium Alloy Machining. (Doctoral dissertation). Uppsala: Acta Universitatis Upsaliensis
Open this publication in new window or tab >>Investigation of Topography, Adhesion and Diffusion Wear in Sliding Contacts during Steel and Titanium Alloy Machining
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aim of the present thesis work is to increase the fundamental knowledge of the tribological contact between the cutting tool and the work material in three different cutting operations, i.e. hard milling of cold work tool steels, turning in 316L stainless steel and turning in Ti6Al4V alloy, respectively. The influence of cutting parameters and tool surface topography on the initial material transfer tendency and resulting wear and wear mechanisms were investigated under well controlled cutting conditions. High resolution scanning electron microscopy (SEM) and surface analysis, including energy dispersive X-ray spectroscopy (EDS), Auger electron spectroscopy (AES) and time-of-flight secondary ion mass spectrometry (ToF-SIMS), were used in order to characterize the worn cutting tools on a sub-µm scale and deepen the understanding of the wear mechanisms prevailing at the tool / work material interface. The characterization work includes the analysis of worn tool surfaces as well as cross-sections of these. Also, the back side of collected chips were analysed to further understand the contact mechanisms between the tool rake face and chip.

The results show that the transfer tendency of work material is strongly affected by the surface topography of the rake face and that an appropriate pre- and post-coating treatment can be used in order to reduce the transfer tendency and the mechanical interaction between a coated cutting tool and 316L stainless steel. The continuous wear mechanisms of the cutting tools were found to be dependent on the work materials and the cutting parameters used. In hard milling of cold work tool steels, polycrystalline cubic boron nitride shows a combination of tribochemical wear, adhesive wear and mild abrasive wear. In the turning of 316L stainless steel and Ti6Al4V alloy, using medium to high cutting speeds/feeds, the wear of cemented carbide is mainly controlled by diffusion wear of the WC phase. Interestingly, the diffusion wear processes differ between the two work materials. In contact with 316L stainless steel crater wear is controlled by atomic diffusion of W and C into the passing chip. In contact with Ti6Al4V crater wear is controlled by the diffusion of C into a transfer work material layer generating a W layer and TiC precipitates which repeatedly is removed by the passing chip. The experimental work and results obtained illustrates the importance of in-depth characterization of the worn surfaces in order to increase the understanding of the degradation and wear of tool materials and coatings in metal cutting operations.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2019. p. 71
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1831
Keywords
Tribology, Metal cutting, Cemented carbide, PCBN, CVD and PVD coatings, Sur-face topography, Wear mechanisms, Diffusion
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-390315 (URN)978-91-513-0705-3 (ISBN)
Public defence
2019-11-01, Ång/10132 Häggsalen, Ångströmslaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2019-10-10 Created: 2019-08-08 Last updated: 2019-11-13
Saketi, S., Bexell, U., Östby, J. & Olsson, M. (2019). On the diffusion wear of cemented carbides in the turning of AISI 316L stainless steel. Wear, 430-431, 202-213
Open this publication in new window or tab >>On the diffusion wear of cemented carbides in the turning of AISI 316L stainless steel
2019 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 430-431, p. 202-213Article in journal (Refereed) Published
Abstract [en]

The present work has studied the wear and wear mechanisms of three different but comparable cemented carbide grades during orthogonal turning of AISI 316L. The influences of WC grain size and cuffing speed on the resulting crater and flank wear have been evaluated by optical surface profilometry and scanning electron microscopy (SEM). The mechanisms behind the crater and flank wear have been characterized on the sub-micrometer scale using high resolution SEM, energy dispersive X-ray spectroscopy (EDS), Auger electron spectroscopy (AES) and time of flight secondary ion mass spectrometry (ToE-SIMS) of the worn cutting inserts and the produced chips. In addition to a dependence on cutting speeds, wear rates were also found to be dependent on the WC grain size. High resolution SEM, AES and ToF-SIMS analysis of the worn cemented carbide within the crater and flank wear regions revealed that the degradation of cemented carbide at higher cutting speeds is mainly controlled by diffusion wear of the WC-phase. This is supported by ToF-SIMS analysis of the back-side of stainless steel chips which reveals the presence of a 10 nm thin W-containing oxide film. The results are discussed and interpreted in the light of the conditions prevailing at the tool-chip interface.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA, 2019
Keywords
Cemented carbide, AISI 316L stainless steel, Turning, Diffusion wear, SEM, AES, ToF-SIMS
National Category
Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:uu:diva-390081 (URN)10.1016/j.wear.2019.05.010 (DOI)000471597300021 ()
Available from: 2019-08-06 Created: 2019-08-06 Last updated: 2019-10-24Bibliographically approved
Saketi, S., Bexell, U., Ostby, J. & Olsson, M. (2018). Wear Behaviour of Two Different Cemented Carbide Grades in Turning 316 L Stainless Steel. In: Shabadi, R Ionescu, M Jeandin, M Richard, C Chandra, T (Ed.), THERMEC 2018: 10th International Conference on Processing and Manufacturing of Advanced Materials. Paper presented at 10th International Conference on Processing and Manufacturing of Advanced Materials Processing, Fabrication, Properties, Applications (THERMEC), JUL 09-13, 2018, Cite Sci Paris, Paris, FRANCE (pp. 2367-2372). TRANS TECH PUBLICATIONS LTD
Open this publication in new window or tab >>Wear Behaviour of Two Different Cemented Carbide Grades in Turning 316 L Stainless Steel
2018 (English)In: THERMEC 2018: 10th International Conference on Processing and Manufacturing of Advanced Materials / [ed] Shabadi, R Ionescu, M Jeandin, M Richard, C Chandra, T, TRANS TECH PUBLICATIONS LTD , 2018, p. 2367-2372Conference paper, Published paper (Refereed)
Abstract [en]

Cemented carbides are the most common cutting tools for machining various grades of steels. In this study, wear behavior of two different cemented carbide grades with roughly the same fraction of binder phase and carbide phase but different grain size, in turning austenitic stainless steel is investigated. Wear tests were carried out against 316L stainless steel at 180 and 250 m/min cutting speeds. The worn surface of cutting tool is characterized using high resolution scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), Auger electron spectroscopy (AES) and 3D optical profiler. The wear of cemented carbide in turning stainless steel is controlled by both chemical and mechanical wear. Plastic deformation, grain fracture and chemical wear is observed on flank and rake face of the cutting insert. In the case of fine-grained, the WC grains has higher surface contact with the adhered material which promotes higher chemical reaction and degradation of WC grains, so chemical wear resistance of the composites is larger when WC grains are larger. The hardness of cemented carbide increase linearly by decreasing grain size, therefore mechanical wear resistance of the composites is larger when WC grains are smaller.

Place, publisher, year, edition, pages
TRANS TECH PUBLICATIONS LTD, 2018
Series
Materials Science Forum, ISSN 0255-5476 ; 941
Keywords
Cemented carbide, Turning, Stainless steel, Chemical wear, plastic deformation
National Category
Manufacturing, Surface and Joining Technology Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:uu:diva-386384 (URN)10.4028/www.scientific.net/MSF.941.2367 (DOI)000468152500390 ()978-3-0357-1208-7 (ISBN)
Conference
10th International Conference on Processing and Manufacturing of Advanced Materials Processing, Fabrication, Properties, Applications (THERMEC), JUL 09-13, 2018, Cite Sci Paris, Paris, FRANCE
Available from: 2019-06-20 Created: 2019-06-20 Last updated: 2019-06-20Bibliographically approved
Saketi, S., Ostby, J. & Olsson, M. (2016). Influence of tool surface topography on the material transfer tendency and tool wear in the turning of 316L stainless steel. Wear, 368-369, 239-252
Open this publication in new window or tab >>Influence of tool surface topography on the material transfer tendency and tool wear in the turning of 316L stainless steel
2016 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 368-369, p. 239-252Article in journal (Refereed) Published
Abstract [en]

The influence of tool surface topography on the initiation and build-up of transfer layers in the orthogonal turning of 316L austenitic stainless steel have been studied under well controlled conditions. Tool materials include CVD Ti(C,N)-Al2O3-TiN and PVD (Ti, ADN-(Al,Cr)(2)O-3 coated cemented carbide inserts prepared using different grinding and polishing treatments. Post-test characterization of the inserts was performed using high resolution scanning electron, microscopy and energy dispersive X-ray spectroscopy. The results show that the transfer tendency of work material is strongly affected by the surface topography of the rake face. For both types of inserts, the initial transfer and the build-up of transfer layers are localised to microscopic surface irregularities on the rake face. Consequently, an appropriate surface treatment of the cemented carbide substrate before coating deposition and the as-deposited CVD and PVD coating can be used in order to reduce the transfer tendency and the mechanical interaction between the mating surfaces. Also, an improved surface finish was found to reduce coating wear and consequently the crater wear rate of the inserts investigated. This can most likely be explained by the reduced tendency to discrete chipping of coating fragments in the contact zone and the formation of a thin transfer layer composed of Al, Si, Ca, O with beneficial friction properties which are promoted by a smooth coating surface.

Keywords
Turning, Material transfer, Surface topography, Coatings, Stainless steel
National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-324504 (URN)10.1016/j.wear.2016.09.023 (DOI)000390733400026 ()
Available from: 2017-06-15 Created: 2017-06-15 Last updated: 2019-10-24Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-5536-3077

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