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Effects of high pressure cooling in the flank and rake faces of WC tool on the tool wear mechanism and process conditions in turning of alloy 718
University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.ORCID iD: 0000-0002-0895-3303
Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
Department of Production Machines and Equipment, Faculty of Mechanica lEngineering, Center of Advanced AerospaceTechnology, CzechTechnical University in Prague, Czech Republic.
Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Swede.
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2019 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 434-435, article id 102922Article in journal (Refereed) Published
Abstract [en]

The exceptional properties of Heat Resistant Super Alloys (HRSA) justify the search for advanced technologiesthat can improve the capability of machining these materials. One such advanced technology is the applicationof a coolant at high pressure while machining, a strategic solution known for at least six decades. The aim is toachieve extended tool life, better chip control and improved surface finish. Another aim is to control the temperature in the workpiece/tool interface targeting for optimum cutting conditions. In most of the existing applications with high-pressure coolant media, the nozzles are positioned on the rake face side of the insert andthey are directed towards the cutting edge (the high-temperature area). The coolant is applied at high-pressureto improve the penetration of the cooling media along the cutting edge in the interface between the insert andworkpiece material (chip) as well as to increase chip breakability. However, the corresponding infusion ofcoolant media in the interface between the flank face of the insert and the work material (tertiary shear zone) hasbeen previously only scarcely addressed, as is the combined effect of coolant applications on rake and clearancesides of the insert. The present work addresses the influence of different pressure conditions in (flank: 0, 4 and8 MPa; rake: 8 and 16 MPa) on maximum flank wear, flank wear area, tool wear mechanism, and overall processperformance. Round uncoated inserts are used in a set of face turning experiments, conducted on the widely usedHRSA "Alloy 718" and run in two condition tests with respect to cutting speed (45 (low) and 90 (high) m/min).The results show that an increase in rake pressure from 8 to 16 MPa has certainly a positive impact on tool life.Furthermore, at higher vc of 90 m/min, cutting edge deterioration: due to an extensive abrasion and crack in thewear zone were the dominant wear mechanism. Nevertheless, the increase in coolant pressure condition to16 MPa reduced the amount of abrasion on the tool compared to 8 MPa. At the lower cutting speed, no crack orplastic deformation or extensive abrasion were found. When using 8 MPa pressure of coolant media on the flank,the wear was reduced by 20% compared to flood cooling conditions. Application of high-pressure cooling on theflank face has a positive effect on tool life and overall machining performance of Alloy 718.

Place, publisher, year, edition, pages
2019. Vol. 434-435, article id 102922
Keywords [en]
Alloy 718, Cemented tungsten carbide, High-pressure coolant, Tool wear mechanism, Crack, Coolant-boiling
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
URN: urn:nbn:se:hv:diva-14330DOI: 10.1016/j.wear.2019.05.037ISI: 000487194500001Scopus ID: 2-s2.0-85070612386OAI: oai:DiVA.org:hv-14330DiVA, id: diva2:1345510
Funder
Knowledge Foundation, 20140130Region Västra Götaland
Note

Funders:ESIF , EU Operational Programme Research , Development and Education; the Centre of Advanced Aerospace Technology ( CZ.02.1.01/0.0/0.0/16_019/0000826 )

Available from: 2019-08-26 Created: 2019-08-26 Last updated: 2020-01-30Bibliographically 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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