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Effect of Process Parameters on the Crack Formation in Laser Metal Powder Deposition of Alloy 718
University West, Department of Engineering Science, Division of Welding Technology. (PTW)ORCID iD: 0000-0002-1472-5489
University West, Department of Engineering Science, Division of Welding Technology. (PTW)ORCID iD: 0000-0001-9065-0741
University West, Department of Engineering Science, Division of Welding Technology.ORCID iD: 0000-0003-2560-0531
University of Manitoba, Department of Mechanical Engineering,Winnipeg, R3T 5V6, Canada.
2018 (English)In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 49A, no 10, p. 5042-5050Article in journal (Refereed) Published
Abstract [en]

Cracking in Alloy 718 using laser metal powder deposition has been evaluated in this study. It is found that the material is susceptible to cracking when the laser power is high, the scanning speed is high and the powder feeding rate is low. Almost all the cracks are located close to the center of the deposited wall and propagates in the normal direction to the substrate. Evidence of liquation are found at the cracked surfaces and since all cracks reside in regions which are reheated several times, the cracks are determined to mostlikely be heat affected zone liquation cracks. The influence of respective process parameter was evaluated using a design of experiment approach. It is shown that, when the powder feeding rate is incorporated as avariable, the heat input is not a suitable indicator for the hot cracking susceptibility in laser metal powder deposition of Alloy 718. A combinatory model using the power ratio together with the heat input is therefore proposed.

Place, publisher, year, edition, pages
2018. Vol. 49A, no 10, p. 5042-5050
Keywords [en]
Laser Metal Deposition, Additive manufacturing, Powder, Superalloy, Cracking, Characterization
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
URN: urn:nbn:se:hv:diva-11841DOI: 10.1007/s11661-018-4767-0ISI: 000443469700064Scopus ID: 2-s2.0-85049122881OAI: oai:DiVA.org:hv-11841DiVA, id: diva2:1161100
Note

Ingår i avhandling och det finns ett tidigare publicerat manuskript.

Available from: 2017-11-29 Created: 2017-11-29 Last updated: 2018-10-25Bibliographically approved
In thesis
1. Laser Metal Deposition using Alloy 718 Powder: Influence of Process Parameters on Material Characteristics
Open this publication in new window or tab >>Laser Metal Deposition using Alloy 718 Powder: Influence of Process Parameters on Material Characteristics
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Additive manufacturing (AM) is a general name used for manufacturing methods which have the capabilities of producing components directly from 3D computeraided design (CAD) data by adding material layer-by-layer until a final componentis achieved. Included here are powder bed technologies, laminated object manufacturing and deposition technologies. The latter technology is used in this study. Laser Metal Powder Deposition (LMPD) is an AM method which builds components by fusing metallic powder together with a metallic substrate, using a laser as energy source. The powder is supplied to the melt-pool, which is created by the laser, through a powder nozzle which can be lateral or coaxial. Both the powder nozzle and laser are mounted on a guiding system, normally a computer numerical control (CNC) machine or a robot. LMPD has lately gained attentionas a manufacturing method which can add features to semi-finished components or as a repair method. LMPD introduce a low heat input compared to conventional arc welding methods and is therefore well suited in, for instance, repair of sensitive parts where too much heating compromises the integrity of the part. The main part of this study has been focused on correlating the main process parameters to effects found in the material which in this project is the superalloy Alloy 718. It has been found that the most influential process parameters are the laser power, scanning speed, powder feeding rate and powder standoff distance.These process parameters have a significant effect on the temperature history ofthe material which, among others, affects the grain structure, phase transformation, and cracking susceptibility of the material. To further understand the effects found in the material, temperature measurements has been conducted using a temperature measurement method developed and evaluated in this project. This method utilizes a thin stainless steel sheet to shield the thermocouple from the laser light. This has proved to reduce the influence of the laser energy absorbed by the thermocouples.

Place, publisher, year, edition, pages
Trollhättan: University West, 2017. p. 104
Series
PhD Thesis: University West ; 12
Keywords
Additive manufacturing; Laser metal deposition; Powder; Superalloy; Material characterization
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-11842 (URN)978-91-87531-68-2 (ISBN)978-91-87531-67-5 (ISBN)
Public defence
2017-12-18, F104, Trollhättan, 10:00 (English)
Opponent
Supervisors
Available from: 2017-11-29 Created: 2017-11-29 Last updated: 2017-11-29Bibliographically approved

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Segerstark, AndreasAndersson, JoelSvensson, Lars-Erik

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