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Microstructural Characterization of Laser Metal Powder Deposited 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. (PTW)ORCID iD: 0000-0003-2560-0531
University of Manitoba,Department of Mechanical Engineering, Winnipeg, R3T 5V6, Canada.
2018 (English)In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 142, p. 550-559Article in journal (Refereed) Published
Abstract [en]

A microstructural study of Laser Metal Powder Deposition (LMPD) of Alloy 718, using a low (40 J/mm) and high (100 J/mm) heat inputs (HIs) was performed. The microstructure was characterized in as-deposited condition as well as after a standard heat-treatment, using optical microscope (OM), scanning electron microscope (SEM) and Transmission Electron Microscope (TEM). Laves, MC-carbides, γ' and γ'' are observed in the interdendritic areas of both conditions. However, the dendritic core only consists of γ-matrix. The high HI condition shows a slightly larger Primary Dendrite Arm Spacing (PDAS) as compared to the low HI condition. Additionally, the particle size of the Nb-rich constituents in the interdendriticregions (Laves-phase and Niobium carbide) are larger in the high HI sample. After heat-treatment, the Laves phase dissolves and is replaced by δ-phase in the interdendritic regions, while γ', γ'' and MC-carbideremain in the interdendritic regions. However, the γ'' precipitates seems to be less developed in the dendritic core as compared to the interdendritic regions, especially in the high HI sample. This can be attributed to a heterogeneous distribution of Nb in the microstructure, with a lower Nb content in the dendritic core as compared to close to the interdendritic regions.

Place, publisher, year, edition, pages
Elsevier, 2018. Vol. 142, p. 550-559
Keywords [en]
Laser Metal Deposition, Additive manufacturing, Powder, Superalloy, Microstructure
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
URN: urn:nbn:se:hv:diva-11840DOI: 10.1016/j.matchar.2018.06.020Scopus ID: 2-s2.0-85048865443OAI: oai:DiVA.org:hv-11840DiVA, id: diva2:1161097
Note

Ingår i avhandling med 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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