Stefan Graefe

Mr. Stefan Graefe

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Research Focus & Metrics

Academic Career Length

10Years (2017-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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7 June 2017 in Coatings
Verified
Journal Article
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FKFritz Klocke
Fritz Klocke
MSMartin Schulz
Martin Schulz
SGStefan Graefe
Stefan Graefe
Laser hardening is a surface hardening process which enables high quality results due to the controllability of the energy input. The hardened area is determined by the heat distribution caused by the intensity profile of the laser beam. However, commonly used top-hat laser beams do not provide an ideal temperature profile. Therefore, in this paper the beam profile, and thus the temperature profile, is optimized using freeform optics. The intensity distribution is modified to generate a top-hat temperature profile on the surface. The results of laser hardening with the optimized distribution are thereupon compared with results using a top-hat intensity distribution.

14 October 2022 in Processes
Verified
Journal Article
Open access
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FGFerdinand Groten
Ferdinand Groten
SGStefan Graefe
Stefan Graefe
TBThomas Bergs
Thomas Bergs
Robert SchmittRobert Schmitt
Robert Schmitt
The automation of cell production processes demands strict requirements with regard to sterility, reliability, and flexibility. Robots work in such environments as transporting devices for a huge variety of disposables, e.g., cell plates, tubes, cassettes, and other objects. Therefore, the blades of their grippers must be designed to hold all of these different materials in a stable, gentle manner, and in defined positions, which means that the blades require complex geometries. Furthermore, they should have as few edges as possible, so as to be easy to clean. In this report, we demonstrate how these requirements can be met by producing stainless steel robot grippers by additive manufacturing.

7 September 2025 in Nuclear Materials and Energy
Verified
Journal Article
Open access
JTJannik Tweer
Jannik Tweer
TDThomas Derra
Thomas Derra
DDDaniel Dorow-Gerspach
Daniel Dorow-Gerspach
Mauricio GagoMauricio Gago
Mauricio Gago
SGSascha Gierlings
Sascha Gierlings
GNGhaleb Natour
Ghaleb Natour

7 August 2026 in Metals
Verified
Journal Article
Open access
PDF file
MDMohammad Dadgar
Mohammad Dadgar
MMMartina Müller
Martina Müller
MMMax Meerkamp
Max Meerkamp
THTim Herrig
Tim Herrig
SGStefan Graefe
Stefan Graefe
TBThomas Bergs
Thomas Bergs
Additive manufacturing (AM) enables rapid, near-net-shape fabrication with high material efficiency, but the resulting components often exhibit surface roughness, microstructural heterogeneity, and tensile residual stresses that reduce their performance. Machine hammer peening (MHP) is a mechanical surface treatment capable of modifying the surface integrity of AM components. It can be applied either as a conventional post-processing step after fabrication or as a hybrid interlayer treatment integrated into the build process. In this study, the effects of MHP process parameters and treatment strategies on wire-based laser metal deposition (LMD-w) Inconel 718 components were investigated, including the implementation of hybrid interlayer MHP. Surface topography, hardness, microstructure, and residual stresses were examined experimentally, while numerical simulations were developed to support the measurements and to characterize local contact conditions and plastic strain evolution during peening. The results show that MHP significantly reduces surface waviness and roughness, increases near-surface hardness, refines the microstructure, and introduces deep compressive residual stresses. Furthermore, hybrid interlayer MHP enhances the depth and uniformity of the modified layer by influencing the evolving microstructure during deposition. Standard forged Inconel 718 samples were also treated with MHP as a reference, showing comparable characteristics between the forged and AM components. These findings demonstrate that MHP is a versatile and effective modification technique for improving the performance and reliability of AM components, particularly when implemented as a hybrid interlayer treatment during the AM process.