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Processes and active zones in oxygen-free atmospheres for the development of sustainable production techniques and manufacturing processes
All technically used inert gas and vacuum atmospheres still contain sufficient oxygen molecules, which lead to the rapid oxidation of metal surfaces. This limits the possibilities of many processing and joining processes. The Collaborative Research Center 1368 "Oxygen-free production" is based on the idea of adding a small amount of silane (a few ppm) to the inert gas argon. The silane reacts with the residual oxygen and water in the atmosphere and reduces the partial pressure of the oxygen to less than 10-23 bar. This partial pressure is equivalent to extremely high vacuums (XHV-adequate atmosphere). The CRC is concerned with the development and research of specific production processes for forming, shaping, joining, cutting and coating in an oxygen-free environment.
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Sub-project C01 "Clarification of mechanisms and processes for the deoxidation of material surfaces and their implementation on a laboratory and pilot plant scale"
Project leader: Prof. Dr. rer. nat. Wolfgang Maus-Friedrichs, Dr. rer. nat. Lienhard Wegewitz
Funding period: 01/2020 - 12/2027
Funding body: DFG
Researchers: M. Sc. Viktor Udachin (01/2020 - 12/2023), B.Sc. Maria Argirusi (01/2024 - 12/2027)
The subproject "C01 - Deoxidation mechanisms" addresses the plasma-chemical and thermal deoxidation of material surfaces for their application in oxygen-free production. The fundamental research and technical implementation of deoxidation processes enables the use of oxide layer-free semi-finished products, especially in the subprojects A01 to A05 and C03 and the transfer project T01 planned for the second funding period. Both the deoxidation and the subsequent processing of the semi-finished products take place in an oxygen-free environment in argon-silane. Sub-project C01 thus enables other sub-projects to exclude interfering oxide layers in production processes. In the first funding period of the Collaborative Research Center (SFB), pure metals, including copper and iron, were plasma-chemically and thermally treated in three different atmospheres of argon (Ar), argon-silane (Ar/SiH4) and argon-hydrogen (Ar/H2). One of the main objectives of the subproject was to investigate the deoxidation effect of the non-thermal plasma by adding silane in argon. The deoxidation results obtained for argon and argon-silane were compared with deoxidation experiments in a different reducing atmosphere of argon hydrogen. In general, it was observed that the addition of silane or hydrogen to argon significantly improves the deoxidation effect of the argon plasma, so that for example for copper an almost complete plasma deoxidation without thermal influence was achieved within a few seconds. Iron surfaces can be almost completely deoxidized by a combination of non-thermal plasma and heating to 200-300 °C. It was shown that at these temperatures and the operating parameters of the dielectric barrier discharge (DBD), other metals such as aluminium or titanium cannot be completely deoxidized. The results of the project therefore indicate that non-thermal plasma deoxidation of copper or iron can be successfully carried out in the XHV-adequate atmosphere. The thermally weakly assisted plasma deoxidation process is therefore an effective deoxidation technique that can easily be introduced into the other processing methods in the XHV-adequate atmosphere. Building on the successes in the deoxidation of copper and iron in the first funding period, the overriding research objective in the second funding period is to expand the range of materials to include practical steels and selected non-ferrous metal alloys. By varying the operating parameters of the plasma and a combination of thermal and plasma-chemical deoxidation, it should be possible to remove oxide layers from materials that previously could not be deoxidized in the DBD, or only to a limited extent. A concept for a combined deoxidation system is being developed and qualified with a view to integrating deoxidation into the respective process chain at a later stage. Based on this, a laboratory-scale demonstrator will be constructed and tested. In addition, new and further developments of the deoxidation modules for other sub-projects of the SFB are part of the work in the project. One example of this is a system for the plasma deoxidation of inserts for composite casting and layer transplantation in the low-pressure casting process, which is being designed and built together with sub-project A01.