Projects

The Cross-Disciplinary Multidimensional Material Analysis project plans to make efficient use of the infrastructure available at OVGU and to promote the targeted further development of multidimensional, coupled methods of scanning electron and ion microscopy with structure elucidation, element analysis and in-situ testing technology in the field of interdisciplinary material development.
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The aim of the project is to develop an alternative hard-phase-reinforced, powder-metallurgically produced tool by developing an iron-based alloy with a hard-phase content of over 50%, which is formed from a molten phase and embedded in a martensitic structure. This is realized by developing at least three alloy types and simulating the formation of the hard material particle fraction in the melt by thermodynamic calculations. Melt metallurgical 25 g samples (melt) are produced in order to investigate the potential for further technical application. The powder from the novel alloys is fractionated to a uniform particle size and pressed into green compacts. The samples are subjected to a machining process (e.g. chipping) and post-processed in a newly developed sintering and heat treatment process. Compared to the state of the art, the hardness of the alloy is increased and costs are reduced at the same time. The target market for this development is tools and products in the agricultural technology sector with around 1,000 potential customer companies.
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As part of the R&D cooperation project "PC4PM - Powder Coatings for Printed Materials", powder coating is to be tested and established for the first time as a surface coating process for additively manufactured materials. The planned development work includes the coating of generatively manufactured plastics and metals with abrasion-resistant powder coatings. This reduces the production-related surface roughness of generatively manufactured components and significantly increases their wear resistance, which contributes to an improvement in component properties in numerous applications. In addition to influencing the look and feel, it is also possible to increase abrasion and wear resistance. The project is also pursuing the development of low-melting powder coatings with low cross-linking temperatures. Lowering the crosslinking temperature would result in a reduction in the process energy required and therefore significant cost and energy savings in the coating process. In addition, the range of applications for powder coating of plastics would be significantly expanded, as the high cross-linking temperatures of powder coatings mean that plastics are currently not suitable for this type of coating
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Background
>> replacement of human joints (implants) becomes more important (demographic change)
>> materials for medical implants offer several challenges and potential for improvements

Objective
>> to offer small-scale solutions for improvements by using in-situ methods to investigate and analyze materials and the related mechanisms for medical implants

Methods
>> mechanical and thermal treatments
>> SEM-EDS (energy dispersive X-ray spectroscopy) / EBSD (electron backscatter diffraction) in-situ methods

Results
>> clarification of phase transformation mechanisms of CoCrMo alloys (requirements, activation, process, consequences)
>> phase-related (microstructure) properties of CoCrMo alloys in various conditions

Conclusions
>> materials science-based recommendations for possible improvements for medical implants with regard to possible changes of chemical composition and/or pre-treatments before implantation

Orignality
>> research at the intersection between mechanical engineering and medicine
>> unique combination of methods (in-situ SEM) and materials (biomedical implants) offers new informative and helpful insights into mechanisms in materials for medical implants

Keywords
CoCrMo, in-situ, Scanning Electron Microscopy (SEM), phase transformation

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For medical joint pairings or endoprostheses, which are made of high-strength and difficult-to-machine materials such as cobalt-chromium-molybdenum, titanium or ceramic, an economical manufacturing process is necessary to guarantee a flawless product. In the case of medical implants, there are sometimes specific requirements for the alloys used (e.g. body-compatible and medically approved materials or resistance to heat development and compressive or tensile stresses) and demands for trouble-free, multi-axis load transmission over several million load cycles and multi-axis motion loading. In order to meet the demands for increasing load cycles, higher rigidity, greater force transmission torques, lower weight, more complex geometries and improved wear behavior, efficient manufacturing processes are to be developed on the basis of fundamental material technology studies. The material Co-Cr-Mo is difficult to machine. After turning and milling, components made of high-strength alloys have to undergo costly and time-consuming grinding and polishing. Nevertheless, the required surface structures and edge zone properties, such as tensile and compressive residual stresses, roughness values and the avoidance of burr formation, can often not be sufficiently achieved. Even with standardized surfaces, signs of wear of the sliding partners become visible. Inadequate surface qualities result in limited functional properties, possible joint fracture and, consequently, complete functional failure of entire body areas.
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