Prof. Dr. Carolin Körner

Chair of Materials Science and Engineering for Metals

Research projects

  • Titanium implants
  • Cellular titanium
  • New processes and alloys
  • Casting
  • Additive manufacturing
  • Alloy development

Current projects

  • Grundlagenuntersuchung zum Pulversmoke-Phänomen beim selektiven Elektronenstrahlschmelzen

    (Third Party Funds Single)

    Term: 1. March 2021 - 29. February 2024
    Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)

    Selective Electron Beam Melting (SEBM) is one of the most promising additive manufacturing technologies for producing high-performance materials, owing to its fast control of the beam position, high power output and energy absorbance as well as low oxidation and contamination risk. Nevertheless, the so-called smoke phenomenon, which results in an explosion-like powder spreading within the whole machine, restricts the further development of SEBM of different materials. So far, methods to prevent smoke event are mainly based on trial-and-error optimization and empirical rules. A basic understanding of powder smoking mechanism is highly desired to exploit the potential of the SEBM process. According to experimental observations at the Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) and at the TsingHua-University (THU), the proposed project is based on the novel hypothesis that powder smoking is initiated by gas evaporation, which can take place at relatively low temperatures under vacuum conditions, followed by an avalanche effect caused by electrostatic charging of the powder bed during SEBM. At FAU, the research focus will lie on the investigation of the effect of gas evaporation, while THU will be committed to discover the influence of powder bed charging during SEBM. Main objectives of the project are to in situ observe the evolution of the whole smoking process and to establish a physical model to explain the smoking mechanism as well as to prevent the powder smoking. First, far-field and near-field ELectron-Optical (ELO) observation system as well as other different process monitoring tools will be used for the in situ observation of smoking at FAU and THU, respectively. Second, in order to evaluate key factors leading to smoking, the effect of powder properties (at FAU) and process parameters (at THU) will be investigated. Third, for physical modelling, recoil pressure induced by gas evaporation (at FAU) and electrostatic repulsive forces caused by powder bed charging (at THU) will be taken into account. Finally, optimized scan strategies and requirements on powder properties can be derived to increase process stability and to allow the use of finer powders. In addition, by analyzing ELO signals a real-time signal processing system will be developed, so that the SEBM process can be promptly interrupted at the initial stage of powder smoking, before the avalanche effect (catastrophic smoke event) occurs.

  • Simulation methods for additive processing of high temperature alloys - microstructure, in-service properties and repair

    (Third Party Funds Single)

    Term: 1. December 2020 - 30. November 2023
    Funding source: Bundesministerium für Wirtschaft und Technologie (BMWi)
  • Intelligent catalyst carrier concept with additively manufactured structures made of shape memory alloys for the optimization of the wall heat transfer in tubular reactors

    (Third Party Funds Single)

    Term: 1. October 2020 - 30. September 2023
    Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)
    Cellular structures represent a promising alternative to classical randomly packed bed reactors owing to their very good heat transport characteristics. A key challenge of using cellular structures as catalyst carriers in tubular reactors is the contact of the structure with the tube wall, which in many cases is not sufficient and thus downgrades the overall heat transfer performance. Especially with strongly exo- or endothermic reactions, this inhibition of heat transfer leads to undesirable temperature gradients. Therefore, the main goal of this proposal is to achieve a scientific understanding for the structure-wall interactions in order to predict the design of an optimal wall coupling. Auxetic POCS (periodic open cellular structures) that are additively manufactured (selective electron beam melting, SEBM) from a shape memory alloy (NiTi, Nitinol) represent a particularly suitable and innovative model system for achieving this goal.The additive manufacturing of these POCS via SEBM offers a great degree of freedom almost without any limitations in the design process. To ensure a good wall coupling for exchangeable catalyst carriers, we propose a system that utilizes the auxetic effect. Uniaxial compression is used to decrease the diameter of the structure. The auxetic effect alone, however, would require a constant pressure to keep the structure compressed. This can be circumvented by combining the auxetic effect with the one-way memory effect of a shape memory alloy. Here, the structure is deformed once before insertion into the reactor and then re-expanded to its original shape by an in situ heat treatment inside the reactor. This method represents an elegant approach for ensuring a press fit between the cellular structure and the reactor wall.The use of Nitinol via SEBM is not sufficiently documented in literature and therefore represents a highly interesting research topic. The combination of knowledge about POCS and literature about additive manufacturing of shape memory alloys offers a promising approach to overcome the problem of wall heat transfer limitations in tubular reactors. Numerical models for mechanical and reaction engineering problems build the framework for the well-founded development of improved catalyst carriers. By performing several optimization cycles the most promising design will be identified. Finally, the feasibility and efficiency of this new concept will be demonstrated in a case study based on a reaction system of technological relevance.
  • Real-time study of electron beam melting of metals

    (Third Party Funds Single)

    Term: 1. July 2020 - 30. June 2024
    Funding source: Bundesministerium für Bildung und Forschung (BMBF)
  • Additive manufacturing of single crystalline superalloys

    (Third Party Funds Group – Sub project)

    Overall project: TRR 103: TRR 103: From Atoms to Turbine Blades - a Scientific Approach for Developing the Next Generation of Single Crystal Superalloys
    Term: 1. January 2012 - 31. December 2023
    Funding source: DFG / Sonderforschungsbereich / Transregio (SFB / TRR)
    URL: http://www.sfb-transregio103.de/

    Project B2 explores selective electron beam melting, which belongs to the additive manufacturing technologies, for the processing of single-crystalline superalloys. Especially the potential of the inherent high cooling rates is investigated. These lead to an ultra-fine and directional solidified microstructure. The main challenge of this project is to develop innovative processing strategies based on a sound theoretical process understanding in order to produce crack-free and preferably single crystalline samples, also with higher geometric complexity.
     

  • Supply of single crystalline Ni- and Co-base superalloys: planning, melting, casting and characterization

    (Third Party Funds Group – Sub project)

    Overall project: TRR 103: From Atoms to Turbine Blades - a Scientific Approach for Developing the Next Generation of Single Crystal Superalloys
    Term: 1. January 2012 - 31. December 2023
    Funding source: DFG / Sonderforschungsbereich / Transregio (SFB / TRR)
    URL: http://www.sfb-transregio103.de/

    The scientific service project of SFB/Transregio 103 takes care of the procurement and processing of all project materials.

  • Single crystalline solidification with enhanced microstructure

    (Third Party Funds Group – Sub project)

    Overall project: TRR 103: From Atoms to Turbine Blades - a Scientific Approach for Developing the Next Generation of Single Crystal Superalloys
    Term: 1. January 2012 - 31. December 2023
    Funding source: DFG / Sonderforschungsbereich / Transregio (SFB / TRR)
    URL: http://www.sfb-transregio103.de/

    Project B1 focuses on the investigation of the newly developed FCBC (Fluidized Carbon Bed Cooling) process for the single crystalline solidification of superalloys. In comparison with commercially available investment casting processes it could be shown that FCBC benefits from a higher cooling potential. In combination with a dynamic baffle a higher axial temperature gradient will evolve. Objective of the upcoming project period is the improvement of the process understanding as well as the process optimization, carried out on a 10 kg prototype plant. A further point of interest is the exploitation of the increased microstructural homogeneity for alloy development.

Recent publications

2023

2022

2021

2020

Related Research Fields

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