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Extending powder particle size distribution of laser powder bed fusion Ti-6Al-4V: investigation of single tracks and multilayer experiments
University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. (KAMPT)ORCID iD: 0000-0003-2857-7154
University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. (KAMPT)ORCID iD: 0000-0003-3772-4371
University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. (KAMPT)ORCID iD: 0000-0001-7991-6369
University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. (KAMPT)ORCID iD: 0000-0002-2185-1774
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2023 (English)Conference paper, Oral presentation with published abstract (Other academic)
Abstract [en]

This paper explores the effects of varying process parameters (i.e., laser power, laser scanning speed, hatch distance) on the characteristics of single tracks, triple tracks and cubes, in order to provide answers to Research Question 1. A full factorial DoE approach was adopted to produce the experiments. Data was extracted from different sources to find correlations between tracks and multilayer geometries. A digital microscope was used to obtain height profiles, whilst polished/etched cross sections cut parallel to the build direction were imaged using a LOM to obtain measurements of track height, width, melt pool depth, subsurface porosity and residual defect content in cubes. Track height was found to exceed the recoated value of 70μm for both single and triple tracks. The width of single tracks showed a clear upward trend when displayed against VED, showing a lateral expansion as energy input increased. It was also revealed that single tracks expand laterally as they grow above the substrate, indicating swelling. The melt pool depth showed a steady upward trend when plotted against LED, though less systematic than track width. A martensitic microstructure was detected, with hierarchical α’ needles growing at prescribed crystallographic directions within vertical prior-β grains. A large portion of spatter particles and unmelted powder granules were detected on the substrate and tracks, with many accumulating on the side of the tracks forming a denudation zone.

Place, publisher, year, edition, pages
2023.
Keywords [en]
extendign powder, laser powder
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
URN: urn:nbn:se:hv:diva-20988OAI: oai:DiVA.org:hv-20988DiVA, id: diva2:1814448
Conference
15th World Titanium Conference, June 2023, Edinburgh, United Kingdom
Note

This paper is under review och will be published in Proceedings.

Available from: 2023-11-24 Created: 2023-11-24 Last updated: 2024-01-08Bibliographically approved
In thesis
1. Investigating the effect of extending powder particle size distribution of Ti-6Al-4V produced by powder bed fusion laser beam process: Influence of process parameters on material integrity
Open this publication in new window or tab >>Investigating the effect of extending powder particle size distribution of Ti-6Al-4V produced by powder bed fusion laser beam process: Influence of process parameters on material integrity
2023 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis focuses on the topic of PBF-LB applied to titanium alloys. Of allalloys, an α + β is chosen, named Ti-6Al-4V. The selection of this particular alloy is driven by its current widespread use in many industrial applications where high strength coupled with low density are both desirable properties. For the last 50 years, parts made with this alloy have been cast or forged and then machined to achieve the final geometry. There is now an opportunity totransform this process chain by additive manufacturing, hence reducing material waste and achieving near net shape from powder feedstock.

The process is summarised as follows: a laser selectively melts areas on a build plate where powder is pre-placed. Then a successive powder layer is spread and the process is repeated until completion. Upon removal of the part from the build plate, loose powder in the chamber is collected and recycled whenever possible. The design freedom provided by powder bed fusion methods enables production of intricate geometries and added functionality, despite the need for post-build consolidation and/or microstructural adjustments.

Today’s fine and narrow powder cuts (e.g., 15-50μm) are designed to be coupled with low layer thicknesses (i.e., 30μm) to achieve smooth surfaces and high resolutions of small features e.g., internal cooling channels. However, costs associated with production of fine and narrow powder cuts are substantial as refinement of batches requires multiple sieving steps. In addition, resulting building times are considerably long (i.e., days), therefore a beneficial alternative could be that of exploring higher layer thicknesses together with wider and coarser powder cuts.

The main idea of this work is to investigate the effects of employing a powder with a wider size distribution 15-90μm. The aim is to reduce the sievingrequired and consequently decrease the costs of developing and building parts made by PBF-LB.

An extensive microstructural investigation is conducted on single tracks and cubes built with 27 different process parameter combinations, which also attempts to establish correlations between characteristics of tracks and responses measured in cubes. As a second step, the amount of residual porosity of asbuilt cubes is chosen as the discriminant for further mechanical testing of sub and super-β transus high-pressure heat treated material.

Abstract [sv]

Den här avhandlingen fokuserar på additiv tillverkning av titanlegeringar med laser pulverbädd metoden. Den legering som främst är i fokus är Ti-6Al-4Vsom är en α+β legering. Anledningen till valet av denna titanlegering är att det är den vanligast förekommande titanlegeringen och att den används i ett antal olika industriella tillämpningar där hög styrka i kombination med låg vikt är önskvärda egenskaper. Under de senaste 50 åren har komponenter utav denna legering tillverkats med gjutning eller smide, följt av bearbetning till slutlig geometri. Med hjälp av additiv tillverkning finns nu en möjlighet att förändra tillverkningskedjan i vilket minskat materialspill och en mer nära-slutgeometri kan erhållas direkt genom användning av metallpulver som utgångsmaterial.

Processen kan summeras enligt följande: en laser smälter ett förbestämt område på en byggplatta som täckts mer pulver. Därefter adderas ytterligare ett lager med metallpulver ovanpå, på vilket samma process sker igen, och igen osv, tills hela detaljen är färdigtillverkad. När detaljen ska tas loss ifrån byggplattan samlas det kvarvarande icke-smälta pulvret upp och återanvänds i så stor utsträckning som möjligt. Frihetsgraderna vid design i processen möjliggör tillverkning av komplexa geometrier och adderade funktionaliteter, även fast efterbehandling och/eller justeringar av mikrostrukturen kan behövas.

Dagens smala pulverstorleksfördelning (tex 15-50μm) är avsedd att ge tunna lagertjocklekar (tex 30μm) för att åstadkomma en fin yta och hög upplösning av små geometrier, såsom exempelvis interna kylkanaler. Men kostnaderna som det innebär att framställa och sortera ut fina och smala kornstorleksfördelningarär avsevärd eftersom det innebär flera steg med silning. Vidare leder de tunnalagertjocklekarna till långa byggtider (typiskt dagar). Ett alternativ, som därför vore fördelaktigt, är att undersöka möjligheten med att bygga tjockare lager med en bredare och större pulverstorleksfördelning.

Huvudfokuset i detta arbete fokuserar på att undersöka effekterna av att använda en bredare pulverpartikelstorleksfördelning 15-90μm, med syfte at minska silningsbehovet och därmed reducera kostnaden för att utveckla och tillverka detaljer med laser pulverbädd additiv tillverkning.

En omfattande mikrostrukturundersökning har gjorts på enkelsträngar och kuber byggda med 27 olika processparameter-kombinationer, vilket samtidigt försöker identifiera korrelationer mellan enkelsträngarnas karaktäristik med resultaten uppmätta hos kuberna. I ett nästa steg har material, som tillverkats med processparametrar som renderade i minst/mest porer hos kuberna, mekaniskt provats efter att det högtrycksvärmebehandlats över- respektive under β-transus.

Place, publisher, year, edition, pages
Trollhättan: University West, 2023. p. 45
Series
Licentiate Thesis: University West ; 43
Keywords
Powder Bed Fusion Laser Beam (PBF-LB), Ti-6Al-4V, Microstructure, Particle Size Distribution (PSD), Productivity Enhancement, Pulverbädd additiv tillverkning (PBF-LB/M), Ti-6Al-4V, Mikrostruktur, Pulverpartikelstorleksfördelning, Produktivitetsförbättring
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-21000 (URN)9789189325562 (ISBN)9789189325555 (ISBN)
Presentation
2023-12-11, J111, Gustava Melins gata, Trollhättan, 13:00 (English)
Opponent
Supervisors
Note

Paper A is not included due to the copyright.

Paper B and C are to be submitted.

Available from: 2023-12-11 Created: 2023-11-27 Last updated: 2024-01-08Bibliographically approved

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Squillaci, LindaNeikter, MagnusHansson, ThomasHarlin, PeterPederson, Robert

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