Revistas
Revista:
AEROSPACE
ISSN:
2226-4310
Recent advances in manufacturing methods have accelerated the exploration of new materials and advantageous shapes that could not be produced by traditional methods. In this context, additive manufacturing is gaining strength among manufacturing methods for its versatility and freedom in the geometries that can be produced. Taking advantage of these possibilities, this research presents a case study involving an electric aerospace actuator manufactured using additive manufacturing. The main objectives of this research work are to assess the feasibility of additively manufacturing electric actuators and to evaluate potential gains in terms of weight, volume, power consumption and cost over conventional manufacturing technologies. To do so and in order to optimise the actuator design, a thorough material study is conducted in which three different magnetic materials are gas-atomised (silicon iron, permendur and supermalloy) and test samples of the most promising materials (silicon iron and permendur) are processed by laser powder bed fusion. The final actuator design is additively manufactured in permendur for the stator and rotor iron parts and in 316L stainless steel for the housing. The electric actuator prototype is tested, showing compliance with design requirements in terms of torque production, power consumption and heating. Finally, a design intended to be manufactured via traditional methods (i.e., punching and stacking for the stator laminations and machining for the housing) is presented and compared to the additively manufactured design. The comparison shows that additive manufacturing is a viable alternative to traditional manufacturing for the application presented, as it highly reduces the weight of the actuator and facilitates the assembly, while the cost difference between the two designs is minimal.
Autores:
Urresti-Ubillos, A. (Autor de correspondencia); Inaki-Arrizubieta-Arrate, J.; Murua-DelaMata, O.; et al.
Revista:
DYNA
ISSN:
0012-7361
Año:
2023
Vol.:
98
N°:
1
Págs.:
45 - 50
The aim of the present research work is the characterization of the 15CDV6 powder material for Laser Directed Energy Deposition (LDED) processes. The novelty of the work lays on the fact that this aeronautical steel has never been employed before in powder LDED process. Therefore, the mentioned steel powder was atomized specifically for the present work and the chemical composition and shape of the particles was measured to ensure the quality of the material. Afterwards, the suitability of the 15CDV6 steel for the L-DED process was studied and the employed methodology consisted of 3 sequential steps: single bead tests, overlapping beads deposition and thin wall construction. The results of each sequence are used as the basis for the following ones. In addition to the determination of the main process parameters, the influence of the deposition strategy on the process efficiency is analyzed and a correlation between the microstructure resulting from the thermal process and the hardness HV0.3 values was obtained. To finish the characterization of the process, a demonstrator part was fabricated using the optimum parameters defined during the tests. Based on the obtained results, the viability of employing 15CDV6 steel in the L-DED process is ensured. Also, it is concluded that if a sufficient cooling rate is ensured, Acicular Ferrite microstructure is obtained, which provides good mechanical properties to the L-DED manufactured parts. Nevertheless, the thermal evolution of the process needs to be controlled in order to avoid heat accumulation and cooling stops are to be applied when required.
Revista:
JOURNAL OF ALLOYS AND COMPOUNDS
ISSN:
0925-8388
Año:
2022
Vol.:
890
Págs.:
161631
Hot Isostatic Pressing (HIP) is a well-known technique that lately is gaining more interest because of its growing involvement in the Additive and Near-Net Shape manufacturing fields. When HIP is used for near net-shape manufacturing, the raw gas atomized powders assume the uttermost importance, and special attention should be given to their quality and characteristics. Based on this statement, the powder should be sieved directly after production to select only those that best suit the HIP process. Typically, a broad Particle Size Distribution is indicated for HIP purposes and looks economically advisable because it leads to a higher yield. Despite this, if the PSD is not strictly controlled, particles with high Oxygen content or chemical inhomogeneity could enter the production chain, leading to compacted components with insufficient mechanical properties. In this paper, Nickel-based superalloy Astroloy particles were assessed in depth both at their surface and in the core, dividing them into sub-batches via mechanical sieving. This procedure evidenced which contribution was brought to the final raw material by each sub-batch. Furthermore, physical properties such as flowability and tap density were studied as a function of the PSD. Next, a complete morphological assessment was conducted to understand the possible defects of each sub-batch better. Similarly, every particle group was chemically studied to determine the Oxygen, Carbon, Nitrogen, and Hydrogen content of each sub-batch. Micro and nano indentations combined with EBSD were used to understand how the particle size may affect the mechanical properties of the powders during the Hot Isostatic pressing. Furthermore, EDS and XRD analysis were used to thoroughly understand how Ti segregation starts forming and what effects are likely to develop. Based on these investigations, it was possible to rationally identify the upper and lower boundary for particle PSD without excessively limiting the overall process yield. (c) 2021 Elsevier B.V. All rights reserved.
Revista:
MATERIALS
ISSN:
1996-1944
Año:
2022
Vol.:
15
N°:
4
Págs.:
1434
Astroloy is a Ni-based superalloy with high-volume fraction of gamma ', which gives high temperature properties but reduces its forgeability. Therefore, powder metallurgy manufacturing processes such as Near Net Shape HIPping are the most suitable manufacturing technology for Astroloy. However, NNSHIP has its own drawbacks, such as the formation of prior particle boundaries (PPBs), which usually tend to decrease material mechanical properties. The detrimental effect of PPBs can be reduced by optimizing the entire HIP processing route. Conventional HIP cycles have very low cooling rates, especially in big components from industry, and thus a series of post-heat treatments must be applied in order to achieve desirable microstructures and improve the mechanical properties. Standard heat treatments for Astroloy are long and tedious with several steps of solutioning, stabilization and precipitation. In this work, two main studies have been performed. First, the effect of the cooling rate after the solutioning treatment, which is driven by the materials' thermal mass, on the Astroloy microstructure and mechanical properties was studied. Experimental analyses and simulation techniques have been used in the present work and it has been found that higher cooling rates after solutioning increase the density of tertiary gamma ' precipitates by 85%, and their size decreases by 22%, which leads to an increase in hardness from 356 to 372 HB30. This hardness difference tends to reduce after subsequent standard heat treatment (HT) that homogenizes the microstructure. The second study shows the effect of different heat treatments on the microstructure and hardness of samples with two different thermal masses (can and cube). More than double the density of gamma ' precipitates was found in small cubes in comparison with cans with a higher thermal mass. Therefore, the hardness in cubes is between 4 and 20 HB 30 higher than in large cans, depending on the applied HT.
Revista:
MATERIALS
ISSN:
1996-1944
Año:
2020
Vol.:
13
N°:
12
One of the main challenges in additive manufacturing (AM) of medical implants for the treatment of bone tissue defects is to optimise the mechanical and biological performance. The use of post-processing can be a necessity to improve the physical properties of customised AM processed implants. In this study, Ti-6Al-4V coupons were manufactured using selective laser melting (SLM) in two build orientations (vertical and horizontal) and subsequently post-processed using combinations of hot isostatic pressing (HIP), sandblasting (SB), polishing (PL) and chemical etching (CE). The effect of the different post-manufacturing strategies on the tensile and fatigue performance of the SLMed parts was investigated and rationalised by observing the surface topography. Vertically built samples showed higher yield strength (YS) and ultimate tensile strength (UTS) than the horizontal samples, increasing from 760.9 +/- 22.3 MPa and 961.3 +/- 50.2 MPa in the horizontal condition to 820.09 +/- 16.5 MPa and 1006.7 +/- 6.3 MPa in the vertical condition, respectively. After the HIP treatment, the ductility was substantially improved in both orientations; by 2.1 and 2.9 folds in the vertical and horizontal orientations, respectively. The vertically built samples demonstrated a superior ductility of 22% following HIP and polishing. Furthermore, chemical etching was found to be the most effective surface post-processing treatment to improve the fatigue performance after HIP, achieving the highest run-out strength of 450 MPa. Most importantly, chemical etching after HIP enhanced the cellular affinity of the surface, in addition to its good fatigue performance, making it a promising post-processing approach for bone implants where tissue integration is needed.
Autores:
Irukuvarghula, S. (Autor de correspondencia); Hassanin, H.; Cayron, C.; et al.
Revista:
ACTA MATERIALIA
ISSN:
1359-6454
Año:
2019
Vol.:
172
Págs.:
6 - 17
The effect of powder size distribution and oxygen content on the extent of multiple twinning and spatial distribution of oxide inclusions in hot isostatic pressed (HIPed) 316L steels was investigated using powders with different characteristics. Modifications to, and differences in their microstructural topology, were tracked quantitatively by evaluating the metrics related to twin related domains (TRDs) on specimens produced by interrupting the HIPing process at various points in time. Results revealed that powder size distribution has a strong effect on the extent of multiple twinning in the fully HIPed microstructure, with specimens produced using narrow distribution showing better statistics (i.e., homogeneously recrystallized) than the ones produced using broad size distribution. The oxide inclusion density in fully HIPed microstructures increased with the amount of oxygen content in the powders while prior particle boundaries (PPBs) were only observed in the specimens that were HIPed using broad powder distribution. More importantly, results clearly revealed that the spatial distribution of the inclusions was strongly affected by the homogeneity of recrystallization. Implications of the results are further discussed in a broader context, emphasizing the importance of utilizing the occurrence of solid state phase transformations during HIPing for controlling the microstructure evolution. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd.
Revista:
ACTA MATERIALIA
ISSN:
1359-6454
Año:
2019
Vol.:
165
Págs.:
520 - 527
A range of heat treatments has been carried out aimed at changing the microstructure and properties of HIPped (Hot Isostatically Pressed) powder Ti-6Al-4V (Ti64). Jet cooling in the HIP has been used to increase the cooling rate from the standard HIP temperature of 930 degrees C, from 5 degrees C/min to 50 degrees C/min. At these cooling rates only a small fraction of the beta present at the HIP temperature transforms to form a dispersion of secondary alpha, whereas when samples are cooled at 200 degrees C/min, much of the beta transforms and contains secondary alpha. The faster cooling leads to increases in tensile and fatigue strength. Additionally, samples have been HIPped or post-HIP heat-treated at 980 degrees C, where there is a large fraction of beta and cooled at the same three rates. Again only a limited fraction of the beta present at the HIP temperature forms secondary alpha when cooled at 5 degrees C/min or 50 degrees C/min, but when cooling at 200 degrees C/min virtually all of the beta transforms to produce secondary alpha. This improves the fatigue and tensile properties significantly. Samples cooled at 200 degrees C/min from 980 degrees C have significantly higher values of microhardness than those cooled from 930 degrees C, both of which are significantly harder than as-HIPped samples. The hardening on cooling at 200 degrees C/min from 980 degrees C is associated with the higher O-content present in the beta just below the transus, which Electron Energy Loss spectroscopy shows is retained in the transformed beta. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.