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Grit Blasting for Removal of Recast Layer from EDM Process on Inconel 718 Shaft: An Evaluation of Surface Integrity
University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. Swerea-IVF AB, 431 22, Mölndal, Sweden. (PTW)ORCID iD: 0000-0003-2991-2911
GKN Aerospace Engine Systems AB, Trollhättan, Sweden.
2016 (English)In: Journal of materials engineering and performance (Print), ISSN 1059-9495, E-ISSN 1544-1024, Vol. 25, no 12, p. 5540-5550Article in journal (Refereed) Published
Abstract [en]

The heat generated during EDM melts the work material and thereby allows large amounts to be removed,but an unfavorable surface of a recast layer (RCL) will also be created. This layer has entirely different properties compared to the bulk. Hence, it is of great interest to efficiently remove this layer and to verify that it has been removed. The main objective of this work has been to study the efficiency of grit blasting forremoval of RCL on an EDM aero space shaft. Additionally, x-ray fluorescence (XRF) has been evaluated asa nondestructive measurement to determine RCL presence. The results show that the grit-blasting processing parameters have strong influence on the ability to remove RCL and at the same time introduce beneficial compressive stresses even after short exposure time. Longer exposure will remove the RCL fromthe surface but also increase the risk that a larger amount of the blasting medium will get stuck into the surface. This investigation shows that a short exposure time in combination with a short grit-blasting nozzle distance is the most preferable process setting. It was further found that handheld XRF equipment can be used as a nondestructive measurement in order to evaluate the amount of RCL present on an EDM surface.This was realized by analyzing the residual elements from the EDM wire.

Place, publisher, year, edition, pages
2016. Vol. 25, no 12, p. 5540-5550
Keywords [en]
Aerospace, EDM, Inconel 718, residual stress, shot blasting, surface integrity, XRF
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
URN: urn:nbn:se:hv:diva-10098DOI: 10.1007/s11665-016-2406-8ISI: 000389272500043Scopus ID: 2-s2.0-84992397193OAI: oai:DiVA.org:hv-10098DiVA, id: diva2:1043731
Funder
VinnovaAvailable from: 2016-10-31 Created: 2016-10-31 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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