| 1. |
- Adegoke, Olutayo, et al.
(författare)
-
Scanning electron microscopy and atom probe tomography characterization of laser powder bed fusion precipitation strengthening nickel-based superalloy
- 2023
-
Ingår i: Micron. - 0968-4328 .- 1878-4291. ; 171
-
Tidskriftsartikel (refereegranskat)abstract
- Atom probe tomography (APT) was utilized to supplement scanning electron microscopy (SEM) characterizationof a precipitation strengthening nickel-based superalloy, Alloy 247LC, processed by laser powder bed fusion (LPBF). It was observed that the material in the as-built condition had a relatively high strength. Using both SEMand APT, it was concluded that the high strength was not attributed to the typical precipitation strengtheningeffect of γ’. In the absence of γ’ it could be reasonably inferred that the numerous black dots observed in thecells/grains with SEM were dislocations and as such should be contributing significantly to the strengthening.Thus, the current investigation demonstrated that relatively high strengthening can be attained in L-PBF even inthe absence of precipitated γ’. Even though γ’ was not precipitated, the APT analysis displayed a nanometer scalepartitioning of Cr that could be contributing to the strengthening. After heat-treatment, γ’ was precipitated and itdemonstrated the expected high strengthening behavior. Al, Ta and Ti partitioned to γ’. The strong partitioningof Ta in γ’ is indicative that the element, together with Al and Ti, was contributing to the strain-age crackingoccurring during heat-treatment. Cr, Mo and Co partitioned to the matrix γ phase. Hf, Ta, Ti and W were found inthe carbides corroborating previous reports that they are MC.
|
|
| 2. |
- Anderberg, Staffan, 1981-
(författare)
-
A study of process planning for metal cutting
- 2009
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Process planning as a function for competitiveness is often neglected. However, as an intermediary between product development and manufacturing, it holds a key function in transforming product specifications and requirements into a producible process plan. Demands and requirements should be met concurrently as manufacturing costs and lead times are minimised. The focus of this thesis is the act of process planning, where the use of better methodologies, computer-aids and performance measurements are essential parts. Since process planning has the function of transforming demands and requirements, changing customer and regulative requirements are vital to regard. Since environmentally benign products and production increases in importance, the research presented in this thesis includes a CNC machining cost model, which relates machining costs to energy consumption. The presented results in this thesis are based on quantitative and qualitative studies in the metal working industry. This thesis has contributed to an enhanced understanding of process planning to achieve better performance and important areas for improvements. Despite a 50 year history of computerised process planning aids, few of these are used in the industry, where manual process planning activities are more common. Process planning aids should be developed around the process planner so that non-value adding activities, such as information management and documentation are minimised in order to allow more resources for value adding activities, such as decision making. This thesis presents a study of systematic process planning in relation to perceived efficiency. This correlation could however not be verified, which opens up for further studies of other possible explanations for process planning efficiency. Process planning improvements in the industry are difficult to make, since there is little focus on process planning activities and limited knowledge about actual performance hereof. This means that measures taken regarding process planning development are difficult to verify.
|
|
| 3. |
- Anderberg, Staffan, 1981-
(författare)
-
Methods for improving performance of process planning for CNC machining : an approach based on surveys and analytical models
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Process planning as an enabler of competiveness is often overlooked, but being one of the principal function in the product realisation flow it holds a key role by combining both product and production requirements into a production concept with respect to the current manufacturing system. As such the capability of process planning to a large extent dictates production cost, lead times, product quality etc. With the introduction of new demands on production, such as environmental impact and process capability, process planning must be able to manage these demands effectively. Accordingly, it is vital to study the effects that up-coming demands have on the act of process planning. The research methods employed in this work include surveys (questionnaires and interviews), industrial case studies and experiments to provide data for models developed. The main finding of this research is that there is a lack of quantified process planning performance knowledge in the industry, which leads to verification problems as to whether changes that are made render anticipated effects. Results of surveys also indicated a low level of digitalisation of product data and limited use of computer aids (CAM, feature-based CAM and PLM) in Swedish industry based on 144 companies' response. A concept to improve process planning performance through operation classification based on process capability indices (Cp/Cpk) was suggested. The role of process planning in designing cost efficient and energy efficient machining operations has been maintained throughout the thesis by showing how tool selection and machining parameters selection influences the possibilities to achieve these objectives. This work has also showed that no inherent contradictions appear to exist between achieving cost efficient and energy efficient machining operations. This thesis has contributed to an enhanced understanding of how process planning improvements can be achieved through a holistic perspective of the process planning function, where both technical and methodological aids are included. It is however essential to understand the current situation of the process planning organisation, its internal/external relations, level of digitalisation, competency level etc. before major changes of the process planning function are undertaken in order to be successful.
|
|
| 4. |
- Andersson, Joel, 1981-, et al.
(författare)
-
Effect of Different Solution Heat Treatments on the Hot Ductility of Superalloys : Part 3 - Waspaloy
- 2013
-
Ingår i: Materials Science and Technology. - 0267-0836 .- 1743-2847. ; 29:1, s. 43-53
-
Tidskriftsartikel (refereegranskat)abstract
- The susceptibility to heat affected zone cracking of Waspaloy has been investigated in terms of its hot ductility, measured as the reduction of area (RA). Gleeble testing with on-heating as well as on-cooling test cycles was carried out to illuminate the influence of different 4 h solution heat treatments between 996 and 1080°C. A ductility maximum of between 80 and 90%RA was found at 1050–1100°C for all conditions in the on-heating tests. Although the different heat treatment conditions showed similar macrohardness, the particle size and distribution of the γ′ and M23C6 phases differed, which significantly affected the on-heating ductility in the lower temperature test region. The ductile to brittle transition was initiated at 1100°C in the on-heating testing with indications of grain boundary liquation at the higher test temperatures. Ductility recovery, as measured in the on-cooling tests from 1240°C, was very limited with <30%RA for all conditions and test temperatures except for the 1080°C/4 h treatment, which exhibited 60%RA at 980°C.
|
|
| 5. |
- Andersson, Joel Håkan, 1981, et al.
(författare)
-
Effect of different solution heat treatments on hot ductility of superalloys Part 2-Allvac 718Plus
- 2012
-
Ingår i: Materials Science and Technology. - : Taylor & Francis Group. - 1743-2847 .- 0267-0836. ; 28:6, s. 733-741
-
Tidskriftsartikel (refereegranskat)abstract
- The hot ductility of Allvac 718Plus for different solution heat treatments (954 degrees C-15 h, 954 degrees C-1 h, 982 degrees C-1 h and 1050 degrees C-3 h+954 degrees C-1 h) has been investigated using Gleeble testing. Substantial variations in the microstructure among the heat treatments affected the Gleeble test hot ductility only to a very limited extent. Constitutional liquation of the NbC phase was found to be the main cause for the poor ductility at high testing temperatures in the on-heating cycle as well as at the lower temperatures on-cooling. Grain boundary delta phase was seen to assist the constitutional liquation of the NbC phase. Based on established evaluation criteria for Gleeble ductility testing, a ranked indicator for weldability is suggested.
|
|
| 6. |
- Andersson, Joel Håkan, 1981, et al.
(författare)
-
Investigation of Homogenization and its Influence on the Repair Welding of Cast Allvac 718Plus
- 2010
-
Ingår i: Proceedings of The 7th International Symposium on Superalloy 718 and Derivatives, TMS (The Minerals, Metals and Materials Society). - Hoboken, NJ, USA : John Wiley & Sons, Inc.. - 9781617827709 ; , s. 439-454, s. 439-454
-
Konferensbidrag (refereegranskat)abstract
- Heat treatment experiments have been carried out to bring understanding to the efficacy of different temperatures and dwell times on the degree of homogenization of the cast Allvac 718Plus alloy which is prone to segregation mainly due to its high content of niobium. The effect of homogenization on weld repair was also examined. The homogenization heat treatment temperatures ranged from 1050°C to 1200°C with 1hr, 5 hrs and 10 hrs dwell times. The degree of homogenization was measured as the reduction of the amount of Laves phase by manual point counting in an optical microscope at high magnification. Longer range, interdendritic, patterns were established through line scan EDS analysis in SEM. It was found that short time (1hr) does not significantly reduce the amount of Laves phase whereas 5 hrs and 10hrs are much more efficient. Interdendritic homogenization does not occur to any measurable extent even at the highest temperature and longest dwell time (1200°C-10hrs) which was also reflected in bulk macro Vickers hardness tests.In the weld repair tests, one of the most homogenized material conditions (1125°C-5hrs +1200°C-10hrs) turned out to be the most prone to cracking while the number of weld cracks after a moderate homogenization heat treatment (1125°C-5hrs) was much smaller .
|
|
| 7. |
- Andersson, Joel, 1981-, et al.
(författare)
-
Hot Cracking of Allvac 718Plus, Alloy 718 and Waspaloy at Varestraint Testing
- 2008
-
Ingår i: 4th International Symposium on Aerospace Materials and Manufacturing Processes. - Montreal : Canadian Institute of Mining, Metallurgy and Petroleum. - 9781617386169 ; , s. 401-413, s. 401-413
-
Konferensbidrag (refereegranskat)abstract
- Varestraint testing together with DSC and SEM-EDX analyses have been performed as means of investigating the hot cracking susceptibility of Allvac 718Plus, alloy 718 and Waspaloy. The solidification sequences in Allvac 718Plus and alloy 718 were very similar to each other starting by an initial solidification of the gamma phase, gamma/MC reaction at around 1260°C and then finally ending the sequence by gamma/Laves eutectic reaction at around 1150°C. Waspaloy had the same solidification sequence, except no Laves phase formation takes place, and solidification started at a somewhat higher temperature as compared to alloy 718 and the solidification sequence ends by a gamma/MC reaction at around 1245°C. The total amount of hot cracking in Waspaloy was shown to be much less than that in alloy 718 and in Allvac 718Plus which is believed to be related to the presence of the Laves eutectic in the latter two alloys with corresponding larger solidification ranges. Hot cracking of 718Plus is slightly less than in 718.
|
|
| 8. |
- Andersson, Joel, 1981-, et al.
(författare)
-
Hot Ductility Study of Haynes 282 Superalloy
- 2010
-
Ingår i: Superalloy 718 and Derivatives. - Hoboken, NJ, USA : The Minerals, Metals, and Materials Society. - 9780470943168 ; , s. 539-554, s. 539-554
-
Konferensbidrag (refereegranskat)
|
|
| 9. |
- Andersson, Joel, 1981-, et al.
(författare)
-
Metallurgical Response of Electron Beam Welded Allvac® 718Plus™
- 2011
-
Ingår i: Hot Cracking Phenomena in Welds III. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783642168635 ; , s. 415-428, s. 415-428
-
Konferensbidrag (refereegranskat)abstract
- Electron beam welding of forged Allvac 718Plus superalloy has been carried out without any visible cracks in weld cross-sections. Healed cracks in the heat affected zone were, however, seen in most cross-sections with the healing as well as the cracking believed to be due to the constitutional liquation of the δ-phase. The δ-phase undergoes constitutional liquation in the Heat Affected Zone (HAZ) and consequently decreases the ductility of the material and renders cracks in the HAZ but due to the large amount of eutectic liquid produced at the same time the healing of the opened cracks takes place.
|
|
| 10. |
|
|
