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Surface integrity after post processing of EDM processed Inconel 718 shaft
University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. Manufacturing Swerea IVF AB Mölndal Sweden. (PTW)ORCID iD: 0000-0003-2991-2911
GKN Aerospace Sweden AB Trollhättan Sweden.
Manufacturing Swerea IVF AB Mölndal Sweden.
University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. (PTW)ORCID iD: 0000-0003-0976-9820
2018 (English)In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 95, no 5-8, p. 2325-2337Article in journal (Refereed) Published
Abstract [en]

Electrical discharge machining (EDM) is considered as an efficient alternative to conventional material removal concepts that allows for much higher material removal rates. However, EDM generates unwanted features such as re-cast layer (RCL), tensile residual stresses and a rough surface. In order to recover the surface integrity, different post processes has been compared: high-pressure water jet (HPWJ), grit blasting (GB) and shot peening (SP). Surface integrity has been evaluated regarding microstructure, residual stresses, chemical content and surface roughness. The results showed that a combination of two post processes is required in order to restore an EDM processed surface of discontinuous islands of RCL. HPWJ was superior for removing RCL closely followed by grit blasting. However, grit blasting showed embedded grit blasting abrasive into the surface. Regarding surface roughness, it was shown that both grit blasting and HPWJ caused a roughening of the surface topography while shot peening generates a comparably smoother surface. All three post processes showed compressive residual stresses in the surface where shot peening generated the highest amplitude and penetration depths. However, the microstructure close to the surface revealed that shot peening had generated cracks parallel to the surface. The results strongly state how important it is to evaluate the surface at each of the different subsequent process steps in order to avoid initiation of cracks.

Place, publisher, year, edition, pages
2018. Vol. 95, no 5-8, p. 2325-2337
Keywords [en]
Surface integrity Inconel 718 Shot peening Abrasive water jet Grit blasting EDM
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
URN: urn:nbn:se:hv:diva-11894DOI: 10.1007/s00170-017-1342-6ISI: 000426055600058Scopus ID: 2-s2.0-85034646822OAI: oai:DiVA.org:hv-11894DiVA, id: diva2:1163586
Funder
Vinnova
Note

First Online: 22 November 2017

Available from: 2017-12-07 Created: 2017-12-07 Last updated: 2020-11-10Bibliographically approved
In thesis
1. Surface integrity on post processed alloy 718 after nonconventional machining
Open this publication in new window or tab >>Surface integrity on post processed alloy 718 after nonconventional machining
2018 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

There is a strong industrial driving force to find alternative production technologies in order to make the production of aero engine components of superalloys even more efficient than it is today. Introducing new and nonconventional machining technologies allows taking a giant leap to increase the material removal rate and thereby drastically increase the productivity. However, the end result is to meet the requirements set for today's machined surfaces.The present work has been dedicated to improving the knowledge of how the non-conventional machining methods Abrasive Water Jet Machining, AWJM, Laser Beam Machining, LBM, and Electrical Discharge Machining, EDM, affect the surface integrity. The aim has been to understand how the surface integrity could be altered to an acceptable level. The results of this work have shown that both EDM and AWJM are two possible candidates but EDM is the better alternative; mainly due to the method's ability to machine complex geometries. It has further been shown that both methods require post processing in order to clean the surface and to improve the topography and for the case of EDM ageneration of compressive residual stresses are also needed.Three cold working post processes have been evaluated in order to attain this: shot peening, grit blasting and high pressure water jet cleaning, HPWJC. There sults showed that a combination of two post processes is required in order to reach the specified level of surface integrity in terms of cleaning and generating compressive residual stresses and low surface roughness. The method of high pressure water jet cleaning was the most effective method for removing the EDM wire residuals, and shot peening generated the highest compressive residual stresses as well as improved the surface topography.To summarise: the most promising production flow alternative using nonconventional machining would be EDM followed by post processing using HPWJC and shot peening.

Place, publisher, year, edition, pages
Trollhättan: University West, 2018. p. 92
Series
Licentiate Thesis: University West ; 20
Keywords
Alloy 718, Non-conventional machining, post processing, surface integrity, Microstructure, Residual stress, Electron back scattering diffraction, Material removal rate
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-12191 (URN)978-91-87531-72-9 (ISBN)978-91-87531-71-2 (ISBN)
Presentation
2018-03-07, C120, Högskolan Väst, Trollhättan, 10:15 (English)
Opponent
Supervisors
Available from: 2018-03-07 Created: 2018-03-02
2. High volumetric machining strategies for superalloy gasturbine components: Comparing conventional and nonconventional machining methods for efficient manufacturing
Open this publication in new window or tab >>High volumetric machining strategies for superalloy gasturbine components: Comparing conventional and nonconventional machining methods for efficient manufacturing
2020 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

There is a strong industrial driving force to find alternative manufacturing technologies in order to make the production of aero engine components of superalloys even more efficient than it is today. Introducing new and nonconventional machining technologies, as well as enhanced utilisation of today's high volumetric manufacturing, allows taking a leap to increase the material removal rate and the productivity. However, the final goal is to meet there quirements set for today's machined surfaces.The objective with the present work has been performed to show how the conventional, Milling, and the non-conventional machining methods, Abrasive Water Jet Machining, AWJM, Laser Beam Machining, LBM, and Electrical Discharge Machining, EDM, affect the surface integrity. This knowledge can beused to define and optimise different manufacturing alternatives for existing orfuture production.The results show that it is possible to use the rough milling to a greater extent if the impact on residuals stresses and deformation is used when determine the machining allowance. This could have a great impact on the productivity.

However, further improvement of the productivity requires an alternative method. For this reason, EDM and AWJM was evaluated and shown to be suitable alternatives to today's manufacturing methods, but both methods require post processing. The results showed that a combination of two post processes is required for addressing issues with residue, topography and residual stresses.The most promising and effective manufacturing strategy would be EDM or AWJM for rough machining followed by post processing either by finish millingor post processing by means of High-Pressure Water Jet Cleaning and shot peening. If EDM and AWJM are to be considered as finish machining operations, further development of the two methods are required.

Place, publisher, year, edition, pages
Trollhättan: University West, 2020. p. 121
Series
PhD Thesis: University West ; 40
Keywords
Alloy 718, High volumetric machining, Conventional and Nonconventional machining, Material removal rate, Post processing, surface integrity, Residual stress, Microstructure, Deformation
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-16010 (URN)978-91-88847-75-1 (ISBN)978-91-88847-74-4 (ISBN)
Public defence
2020-11-04, Albertssalen, 10:00 (English)
Opponent
Supervisors
Available from: 2020-11-11 Created: 2020-11-10 Last updated: 2020-11-10Bibliographically approved

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Holmberg, JonasBeno, Tomas

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