Periodic Reporting for period 2 - ATLAS (Advanced Design of High Entropy Alloys Based Materials for Space Propulsion)
Berichtszeitraum: 2022-01-01 bis 2023-12-31
Space has always stimulated excited explorers, scientists and engineers, and since the Second Post-War period space exploration has been a key technological sector, also inspiring movies that strongly impressed the cultural life of our society, such as the famous Kubrick's movie 2001, A Space Odyssey.
Since that time, and since to humans touched the Moon, space explorations and space missions have gained a more and more important role in our society. Initially, the design of space systems able to work safe and reliably has been characterized by a huge innovation rate in terms of materials, emerging technologies and scientific knowledge of the human behavior in an extreme environment. Today, due to the ever-increasing importance of communications in everyday life, the space sector is also increasingly impacting our everyday life, economy, safety and security and can be considered a pillar for maintaining a prior position in the worldwide competition. Due the increased importance of the space sector, the present space sector framework presents many more actors with respect of the past, both governmental, private companies and public-private partnerships, making competition in space more and more severe. This means that for remaining competitive new disruptive solutions are needed for deep-space missions, satellite installations and for the construction of space infrastructures. The introduction of new materials, able to improve the behavior and the strength of the present ones in the extreme conditions related to space is a key factor to this aim, especially as regards the propulsion systems: the development of next generation space exploration systems requires high temperature materials able to guarantee low density, high strength and ductility, oxidation resistance, good creep properties: High Entropy Alloys (HEA) are an excellent candidate for possible replacement for superalloys.
However, HEAs are relatively new class of materials and, in order to exploit these advancements on HEA, further research and development is needed.
The goal of ATLAS is to take over the present limitations and unsolved issues that limit the utilization of HEA through multidisciplinary materials design framework that advances the state-of-the-art of High Entropy Alloys and related materials compounds towards the emerging practical needs of the space propulsion industry.
To achieve this ambitious result the following challenges have bene addressed, starting from the definition of an accurate material property database and design of the HEA.
To produce the HEA materials and related compounds materials designed within the project, two conceptually different additive manufacturing processes (Selective Laser Melting (SLM) and Cold Spray (CS)) have been used from the production of coupons and samples to the final full scale demonstration.
Since that time, and since to humans touched the Moon, space explorations and space missions have gained a more and more important role in our society. Initially, the design of space systems able to work safe and reliably has been characterized by a huge innovation rate in terms of materials, emerging technologies and scientific knowledge of the human behavior in an extreme environment. Today, due to the ever-increasing importance of communications in everyday life, the space sector is also increasingly impacting our everyday life, economy, safety and security and can be considered a pillar for maintaining a prior position in the worldwide competition. Due the increased importance of the space sector, the present space sector framework presents many more actors with respect of the past, both governmental, private companies and public-private partnerships, making competition in space more and more severe. This means that for remaining competitive new disruptive solutions are needed for deep-space missions, satellite installations and for the construction of space infrastructures. The introduction of new materials, able to improve the behavior and the strength of the present ones in the extreme conditions related to space is a key factor to this aim, especially as regards the propulsion systems: the development of next generation space exploration systems requires high temperature materials able to guarantee low density, high strength and ductility, oxidation resistance, good creep properties: High Entropy Alloys (HEA) are an excellent candidate for possible replacement for superalloys.
However, HEAs are relatively new class of materials and, in order to exploit these advancements on HEA, further research and development is needed.
The goal of ATLAS is to take over the present limitations and unsolved issues that limit the utilization of HEA through multidisciplinary materials design framework that advances the state-of-the-art of High Entropy Alloys and related materials compounds towards the emerging practical needs of the space propulsion industry.
To achieve this ambitious result the following challenges have bene addressed, starting from the definition of an accurate material property database and design of the HEA.
To produce the HEA materials and related compounds materials designed within the project, two conceptually different additive manufacturing processes (Selective Laser Melting (SLM) and Cold Spray (CS)) have been used from the production of coupons and samples to the final full scale demonstration.
Initially, a preliminary evaluation has been performed to connect the industrial requirements to computational efforts based on the application of satellite thrusters. Distilled from the requirements in aspects of performance and processing, a quantitative figure-of-merit for HEA materials properties and the benchmark HEA materials have been summarized and delivered. Prototypes of the HEAs within the identified design space have been produced and preliminarily assessed experimentally. By utilizing the Materials by DesignTM approach and the existing ICME models, a preliminary optimal composition has been computationally designed. Based on the designed composition, powders will be procured and manufactured into test samples.
An assessment of the gap between demands and existing modelling capabilities has been performed, based on which advanced modelling activities and composition designs was performed in WP2.
Based on the technical drawings of existing thrusters provided by Dawn Aerospace, a preliminary assessment of the possible design criticalities related to the additive manufacturing processes that are expected to be used, Laser Powder Bed Fusion (LPBF) and Cold Spray (CS). This preliminary activity involves both the review of the final layout and also preliminary printing of not-functional prototypes to evidence possible critical points during manufacturing, thus correcting the problems in view of using the selected HEA.
However, the project suffered some issues that delayed its development and limited the results. After having designed the first HEA, the time for the production was much more than expected and the application showed some problems: as regards SLM evident cracking was observed, referring to CS the adhesion and the efficiency were very limited. After having corrected the chemical composition, the second version of the HEA requested a relevant time for the delivery and the experimental results showed that the initial problems were solved only partially.
However, in this case the experimental tests on the thruster built by means of SLM were organized and done: even if the results were not fully satisfactory, it was possible to obtain from those tests data that will be exploited in the next future for a further development of these materials.
As regards cold spray, the very limited ductility of the developed HEAs, impeded good condition for powder adhesion (cold spray is solid state powder deposition technique based on the severe plastic strain at high strain rate that take place during the impact of the powder against the substrate. However, an alternative way to proceed was defined; this latter considers to spray a mixture of HEA (80%) with Ti (20%). The role of Ti is to improve the adhesion condition and to entrap the HEA particles to finally have a thin coating able to resist to extreme temperature or a free standing thruster completely made with this mixture of powder. Unfortunately, no time was left for testing the thruster in extreme conditions but the results, in term of mechanical and microstructural characterization were satisfactory.
An assessment of the gap between demands and existing modelling capabilities has been performed, based on which advanced modelling activities and composition designs was performed in WP2.
Based on the technical drawings of existing thrusters provided by Dawn Aerospace, a preliminary assessment of the possible design criticalities related to the additive manufacturing processes that are expected to be used, Laser Powder Bed Fusion (LPBF) and Cold Spray (CS). This preliminary activity involves both the review of the final layout and also preliminary printing of not-functional prototypes to evidence possible critical points during manufacturing, thus correcting the problems in view of using the selected HEA.
However, the project suffered some issues that delayed its development and limited the results. After having designed the first HEA, the time for the production was much more than expected and the application showed some problems: as regards SLM evident cracking was observed, referring to CS the adhesion and the efficiency were very limited. After having corrected the chemical composition, the second version of the HEA requested a relevant time for the delivery and the experimental results showed that the initial problems were solved only partially.
However, in this case the experimental tests on the thruster built by means of SLM were organized and done: even if the results were not fully satisfactory, it was possible to obtain from those tests data that will be exploited in the next future for a further development of these materials.
As regards cold spray, the very limited ductility of the developed HEAs, impeded good condition for powder adhesion (cold spray is solid state powder deposition technique based on the severe plastic strain at high strain rate that take place during the impact of the powder against the substrate. However, an alternative way to proceed was defined; this latter considers to spray a mixture of HEA (80%) with Ti (20%). The role of Ti is to improve the adhesion condition and to entrap the HEA particles to finally have a thin coating able to resist to extreme temperature or a free standing thruster completely made with this mixture of powder. Unfortunately, no time was left for testing the thruster in extreme conditions but the results, in term of mechanical and microstructural characterization were satisfactory.
The conclusions that can be drawn are that the development of HEAs for extreme application like space thrusters deserve further attention for being implemented.
It is underlined that the initial study for the design of a suitable HEA and for the undestaning of its behaviour in extreme conditions by means of the computationmal technique Phyisics of Failure lead to new knowledge and undestanding, published in relevant scientific journals.
Despite the encountered issues, ATLAS allowed a great step beyond the present state of the art by highlighting the great potential of these materials and, at the same time, the present technological limitations to be overcome.
In particular, the problems related to SLM and CS application are now clear and the ATLAS results can be exploited to overcome the present limitations toward the final design and construction of new space thrusters with superior performance and durability.
The achievements of the project can be exploited also in different fields of applications, such as energy and aeronautics, for the design of more efficient systems, which wil be exploited by the European society.
Furthermore, the publication of the results on prestigious scientific journals proves at the same time the quality of the work done and offers the opportunity to exploit the results by the scientific community.
It is underlined that the initial study for the design of a suitable HEA and for the undestaning of its behaviour in extreme conditions by means of the computationmal technique Phyisics of Failure lead to new knowledge and undestanding, published in relevant scientific journals.
Despite the encountered issues, ATLAS allowed a great step beyond the present state of the art by highlighting the great potential of these materials and, at the same time, the present technological limitations to be overcome.
In particular, the problems related to SLM and CS application are now clear and the ATLAS results can be exploited to overcome the present limitations toward the final design and construction of new space thrusters with superior performance and durability.
The achievements of the project can be exploited also in different fields of applications, such as energy and aeronautics, for the design of more efficient systems, which wil be exploited by the European society.
Furthermore, the publication of the results on prestigious scientific journals proves at the same time the quality of the work done and offers the opportunity to exploit the results by the scientific community.