| 1. |
- Linder, Clara, et al.
(författare)
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Corrosion resistance of additively manufactured aluminium alloys for marine applications
- 2024
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Ingår i: npj Materials Degradation. - : Springer. - 2397-2106. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Additive manufacturing opens new possibilities for designing light-weight structures using aluminium alloys. The microstructure of two Al alloys and their corrosion resistance in NaCl and natural seawater environments were investigated. The newly designed Al-Mn-Cr-Zr based alloy showed a higher corrosion resistance than reference AlSi10Mg alloy in both environments in as printed and heat-treated conditions. The corrosion initiated in the Al matrix along the precipitates in the alloys where the Volta potential difference was found the highest. The coarser microstructure and precipitate composition of the new Al-alloy led to the formation of a resistant passive film which extended the passivity region of the Al-Mn-Cr-Zr alloy compared to the AlSi10Mg alloy. The effect of heat treatment could be seen in the microstructure as more precipitates were found in between the melt pool boundaries, which affected the corrosion initiation and slightly the pitting resistance. Overall, this study shows that a newly designed Al-alloy for additive manufacturing has a suitable corrosion resistance for applications in marine environments.
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| 2. |
- Borgström, Henrik, 1975, et al.
(författare)
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Possibilities and constraints of implementing starch consolidated high speed steel in prototyping
- 2008
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Ingår i: Materials Science & Engineering. - : Elsevier BV. - 0921-5093 .- 1873-4936. ; 475:1-2, s. 34-38
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Tidskriftsartikel (refereegranskat)abstract
- In the starch consolidation (SC) process, a water-based slurry containing powder, starch, dispersant and thickener is used to fabricate near net-shape green bodies that are de-binded and further consolidated by sintering. In this study, gas atomized M3/2 as well as high and low carbon V-rich M4 type high speed steel powder (<150 mu m) are considered, Both material types undergo high volumetric shrinkage during super-solidus liquid phase sintering enabling them to reach near full density. The analyses and the review cover different process aspects like: recipe optimisation, post-gelatinization drying, de-binding and sintering. A SC recipe consisting of 58 vol.% powder, 3 vol.% starch, 1 vol.% dispersant and a thickener solution resulted in a density of >98% than what is theoretically stated after sintering. It is found that the success of the post-gelatinization drying procedure depends on the smoothness of mould material and controlling powder oxidation. The best combination was freeze drying the slurry in a silicon rubber mould. For V-rich alloys a total or partial control of eutectic carbides in the final microstructure could be realized for vacuum and nitrogen sintering atmospheres, respectively.
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| 3. |
- Frisk, Karin, et al.
(författare)
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Characterisation of EBM-built shelled samples of Ti6Al4V compacted by HIP
- 2016
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Ingår i: World PM 2016 Congress and Exhibition. - : European Powder Metallurgy Association (EPMA). - 9781899072484
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Konferensbidrag (refereegranskat)abstract
- Compaction of additively manufactured Ti6Al4V components by Hot Isostatic Pressing (HIP) is often applied to eliminate porosity, producing fully dense material. In the present work shelled samples produced by Electron Beam Melting with the Arcam process (EBM) were compacted by HIP to produce fully dense samples. Cylindrical samples were studied. The walls of the cylinders were built with EBM, and the powder from the process was left uncompacted inside the cylinders. Samples with different wall thicknesses were produced. The samples were thereafter subjected to a HIP compaction. The critical wall thicknesses needed for compaction were evaluated, and the microstructures characterized. The results show that fully dense samples, with very fine microstructures, are possible.
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| 4. |
- Leicht, Alexander, 1987, et al.
(författare)
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As-HIP microstructure of EBM fabricated shell components
- 2016
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Ingår i: World PM 2016 Congress and Exhibition. - : European Powder Metallurgy Association (EPMA). - 9781899072484
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Konferensbidrag (refereegranskat)abstract
- Electron Beam Melting (EBM) was used to build Ti-6Al-4V cylindrical shell samples with different wall thickness filled with powder. Built shell samples were HIPed and the difference in microstructure between the EBM-built walls and densified powder inside the shell components was studied as well as the cohesion between these two regions. Components characterization utilizing LOM and SEM+EBSD indicates that columnar grain growth was consistent before and after HIP in the EBM-built part of the components (walls), whereas the densified material in the center of the component had a fine isotropic microstructure, characteristic for HIPed material. The combination of EBM and HIP is shown to be an attractive way of manufacturing complex-shape full density components for high performance applications, involving shortening of built time in the EBM-processing and lead time in capsule fabrication for HIP.
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| 5. |
- Malakizadi, Amir, 1983, et al.
(författare)
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Effects of workpiece microstructure, mechanical properties and machining conditions on tool wear when milling compacted graphite iron
- 2018
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Ingår i: Wear. - : Elsevier. - 0043-1648 .- 1873-2577. ; 410-411, s. 190-201
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present study was to investigate the tool performance when machining compacted graphite iron (CGI) alloys. A comparison was made between solid solution strengthened CGI including various amounts of silicon (Si-CGI) and the pearlitic-ferritic CGI as a reference material. The emphasis was on examining the influence of microstructure and mechanical properties of the material on tool wear in face milling process. Machining experiments were performed on the engine-like test pieces comprised of solid solution strengthened CGI with three different silicon contents and the reference CGI alloy. The results showed up-to 50% lower flank wear when machining Si-CGI alloys, although with comparable hardness and tensile properties. In-depth analysis of the worn tool surfaces showed that the abrasion and adhesion were the dominant wear mechanisms for all investigated alloys. However, the better tool performance when machining Si-CGI alloys was mainly due to a lower amount of abrasive carbo-nitride particles and the suppression of pearlite formation in the investigated solid solution strengthened alloys.
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| 6. |
- Nayyar, Varun, 1981, et al.
(författare)
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Investigation of microstructure and material properties for 18 different graphitic cast iron model materials with focus on Compacted Graphite Iron (CGI)
- 2013
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Ingår i: International Journal of Microstructure and Materials Properties. - : InderScience Publishers. - 1741-8410 .- 1741-8429. ; 8:4-5, s. 262-282
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Tidskriftsartikel (refereegranskat)abstract
- The higher mechanical strength of Compacted Graphite Iron (CGI) than Flake Graphite Iron (FGI) makes it very useful material for several commercial components. The knowledge of microstructure and hence the mechanical properties and machinability is very important for the CGI to used efficiently in manufacturing. The complex geometry of cast components makes it difficult to produce adequate microstructure in the whole component. Adequate material properties can be achieved by having good knowledge about the correlations between the casted geometry, graphite morphology and pearlite content. In the presented paper, 18 different model materials have been analysed extensively, concerning the effect of chemical composition, solidification and cooling rate on the nodularity, pearlite content, interlamellar spacing in pearlite, hardness and mechanical properties. Later, the cutting force measurement tests were performed on some of the materials and it was found that the forces have a strong positive correlation with pearlite content and the tensile strength of the materials.
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| 7. |
- Strondl, Annika, et al.
(författare)
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Innovative powder based manufacturing of high performance gears
- 2016
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Ingår i: World PM 2016 Congress and Exhibition. - : European Powder Metallurgy Association (EPMA). - 9781899072484
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Konferensbidrag (refereegranskat)abstract
- There are strong driving forces towards high-performance gear wheels which can handle higher engine outputs, or allow more compact designs of transmissions. Today the performance and life of conventionally manufactured gear wheels are limited by factors such as inhomogeneous microstructure and distribution of inclusions. Powder metallurgy (PM) can solve some of these problems but has so far had limitations caused by porosity. In this paper a cost effective way to eliminate porosity by HIP-ing without canister has been evaluated with encouraging results. Parameters such as powder particle size, lubricant and double pressing have been evaluated in the PM route in order to get a gas tight surface enabling effective post HIP-ing. So far double pressing has given promising results. Challenges such as open porosity, surface porosity and inclusions are addressed in the paper.
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| 8. |
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| 9. |
- Vattur Sundaram, Maheswaran, 1987, et al.
(författare)
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Experimental and finite element simulation study of capsule-free hot isostatic pressing of sintered gears
- 2018
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Ingår i: International Journal of Advanced Manufacturing Technology. - : Springer Science and Business Media LLC. - 0268-3768 .- 1433-3015. ; 99:5-8, s. 1725-1733
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Tidskriftsartikel (refereegranskat)abstract
- A novel approach to reach full density in powder metallurgy (PM) components is demonstrated in this work. Water-atomised Mo-prealloyed steel powder is utilised for manufacturing cylindrical and gear samples through double pressing and double sintering (DPDS) process route. The effect of sample geometry and powder size fraction on densification is investigated and it is found that the DPDS route enables a density level of > 95% which is sufficient to eliminate the surface open pores. Reaching such high density is necessary, in order to perform capsule-free hot isostatic pressing (HIP). After HIP, full densification is achieved for the cylindrical samples and only near full density is realised for the gears resulting in neutral zone formation due to the density gradient. In order to predict the densification behaviour during the compaction, FEM simulations considering the gear geometry are performed for both the pressing stages and HIP. The simulation predicted a similar densification behaviour with the formation of the neutral zone. The proposed DPDS route with capsule-free HIP in combination with FEM simulation is demonstrated as a potential route for manufacturing full-density PM steel components, e.g. gears, suitable for high-performance applications.
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| 10. |
- Licea Jimenez, Liliana, 1977, et al.
(författare)
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MWNT reinforced melamine-formaldehyde containing alpha-cellulose
- 2007
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Ingår i: Composites Science and Technology. - : Elsevier BV. - 0266-3538 .- 1879-1050. ; 67, s. 844-854
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Tidskriftsartikel (refereegranskat)abstract
- Multi-wall carbon nanotubes (MWNT) were used as reinforcement for melamine-formaldehyde (MF). They were oxidised in HNO3/ H2SO4 mixture and analyzed by means of X-ray Photoelectron Spectroscopy (XPS). Two anionic surfactants: sodium dodecyl sulphate (SDS) and sodium dodecylbenzenesulfonate (NaDDBS) were used to assist the dispersion of nanotubes. The MWNT content was varied from 0 to 1.0 wt%, and the influence of nanotubes on viscosity (flow curves) was measured. The viscosity of SDS-assisted aqueous solution of MF containing a small amount (0.1 wt%) of MWNT is low, and thus promising towards manufacturing processes. A film stacking-like manufacturing route was adapted to prepare ternary MWNT/cellulose/MF thin composite layers. Transmission electron microscopy (TEM) and Light microscopy (LM) were used to observe dispersion. The addition of 0.1 wt% MWNT assisted with SDS increased the storage modulus and tensile strength by 50%. Conventional calculations of the Young's modulus were made. Values underestimating the modulus were found. The observed discrepancy was attributed to polymer chain immobilisation as a result of crosslinking.
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