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Investigation of micro-textured cutting tools used for face turning of alloy 718 with high-pressure cooling
University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. (PTW)ORCID iD: 0000-0002-0895-3303
Czech Technical University in Prague, Research Center of Manufacturing Technology, Prague, Czech Republic.
Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.ORCID iD: 0000-0003-0976-9820
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2019 (English)In: Journal of manufacturing processes, ISSN 1526-6125, Vol. 37, p. 606-616Article in journal (Refereed) Published
Abstract [en]

There is an increasing demand to improve the service life of cutting tools during machining of heat resistant superalloys (HRSA). Various studies showed that textured cutting tools improved the tribological properties and reduced cutting forces, temperature, and tool wear. Surface texturing can be seen as a futuristic design to improve the performance of the cutting tool and to increase productivity. However, only limited research has been conducted in machining superalloys with textured inserts and high-pressure coolant. In this work, three different micro texture designs on both rake and flank face are investigated in combination with high-pressure coolant in machining Alloy 718. Due to better tool life predictability, carbide cutting tools are used in machining components made from superalloys. However, the disadvantage is that machining can only be done at lower cutting speed/feed rate/depth of cut with high tool wear rates. The experimental investigation using different tool wear analysis methods showed that the combination of a cylindrical dimple on the rake and the square pyramid texture on the flank surface improved the wear resistance of the tool. An increase in tool life of about 30% was achieved as compared with a regular insert for the investigated cutting conditions. Different levels of adhering workpiece material were observed on the rake face of textured tools. Furthermore, the chip backside showed imprints from the tool textures. The tool textures on the rake face have influenced the tool-chip friction conditions during cutting.

Place, publisher, year, edition, pages
Elsevier, 2019. Vol. 37, p. 606-616
Keywords [en]
Alloy 718Face turningHigh-pressure coolantNext generation cutting toolsTextured insertsTool wear
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
URN: urn:nbn:se:hv:diva-13430DOI: 10.1016/j.jmapro.2018.12.023ISI: 000465052000058Scopus ID: 2-s2.0-85060085875OAI: oai:DiVA.org:hv-13430DiVA, id: diva2:1280756
Funder
Region Västra GötalandKnowledge Foundation, 20140130Available from: 2019-01-21 Created: 2019-01-21 Last updated: 2020-02-04Bibliographically approved
In thesis
1. Enhanced heat transfer and tool wear in high-pressure coolant assisted turning of alloy 718
Open this publication in new window or tab >>Enhanced heat transfer and tool wear in high-pressure coolant assisted turning of alloy 718
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Förbättrad värmeavledning och verktygsslitage vid högtryckskyld svarvning av legering 718
Abstract [en]

Heat generated in a machining process is a common and critical obstacle faced in today's manufacturing industries. The heat generated in the cutting zone has adirect negative influence on the tool life, which, in turn contributes to increasing the manufacturing costs. Especially in the machining of Heat Resistant Superalloys, HRSA, this is a very limiting factor. HRSA are capable of retaining their mechanical strength and hardness at elevated temperatures. This property is advantageous for applications such as aero-engines, but also a disadvantage, since it also lowers the machinability significantly.This work is an attempt to improve the heat transfer from the cutting zone, which would lead to an increase in the tool life. To achieve this goal, the effect of cooling the flank face (tertiary shear zone) with high-pressure is studied; furthermore, the cutting tool has been modified to create an improved interface between the high pressure coolant and the tool where high-temperature gradient exists.Three main generations of inserts have been designed and investigated. Firstly, an insert with surface texture features created with the purpose of increasing the available surface area for heat dissipation: First generation, Gen I. Secondly, GenI+, a modified rake design of Gen I, for improved frictional conditions on the tool-chip contact. Thirdly, Gen II was designed as a further improvement of GenI. Here, several channel features on the rake face were added, reaching out from the contact zone to the near proximity of the cutting edge. This has the purpose of improving access of the coolant closer to the cutting edge.The experiments were conducted in facing operations of Alloy 718 with uncoated round carbide inserts. All experiments were carried out with high-pressure coolant, with a maximum available pressure of 16 MPa on the rake face and 8MPa on the flank face, respectively. The three generations of inserts, Gen I, I+and II, were experimentally evaluated by tool wear analysis in comparison with a regular insert. The results shows that the tool life increased significantly for the Gen I insert, compared to catastrophic failure of the regular insert at the same conditions. Regarding the Gen II insert, an increase in tool life by approximately30-40 percent, compared to Gen I inserts was observed. XRegarding the coolant-boiling phenomenon, results revealed the existence in form of dark region (Ca precipitate) below the flank wear land. The location and size of the coolant-boiling region is interrelated between flank wear, cutting zone temperature, coolant pressure and vapour pressure of the coolant at the investigated coolant pressure levels. The coolant applied at a pressure lower than the vapour pressure of the coolant itself will cause the "Leidenfrost effect" to appear that will effectively act as a coolant barrier region. However, most importantly, this effect led to the observation of a new wear mechanism present "Cavitation Wear". This type of wear appears in the form of erosion pits on the flank surface of the insert and it is observed for flank pressure conditions of 4and 8 MPa. It is a new phenomenon in tool wear to be seen on uncoated WC cutting tools during machining operations with high-pressure coolant.

Place, publisher, year, edition, pages
Trollhättan: University West, 2019. p. 118
Series
PhD Thesis: University West ; 31
Keywords
Alloy 718; Cavitation; Coolant-boiling; High-pressure coolant; Heat dissipation, Leidenfrost effect; Textured insert; Tungsten carbide; Tool life; Tool wear
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-14663 (URN)978-91-88847-42-3 (ISBN)978-91-88847-41-6 (ISBN)
Public defence
2019-11-22, Albertssalen, 10:00 (English)
Opponent
Supervisors
Available from: 2019-10-30 Created: 2019-10-30 Last updated: 2019-10-30Bibliographically approved

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Tamil Alagan, NageswaranBeno, Tomas

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