Coarse Grain in Case-Hardening Steels – Mechanisms, Effects, and Mitigation Measures Regarding the Fatigue Strength of Powertrain Components
Research Topic
| Short Title | Coarse Grain II |
| Start of Project | Q1/2026 |
| Funding | FVA-Nr. 848/II, IGF-Nr. 01IF24735N Federal Ministry for Economic Affairs and Energy, BMWE |
| Project Partner | Leibniz-Institut für Werkstofforientierte Technologien, IWT |
| Contact | Dr.-Ing. T. Tobie |
Project Description
For the load‑appropriate design of case‑hardened components, such as gears and shafts, reliable knowledge of the influence of grain size on load‑carrying capacity is essential. However, the current state of knowledge regarding the assessment of grain‑size effects remains incomplete. The objective of this project is therefore to expand the scientific basis concerning the mechanisms responsible for the formation of microstructures with increased coarse‑grain fractions, as well as their effects on the load‑carrying capacity of case‑hardened components. In this context, interactions with additional microstructural properties (e.g., residual stresses) will also be examined to enable a comprehensive assessment of the microstructural condition.
To achieve the research objective, the Gear Research Centre (FZG, Technical University of Munich, FE 1) contributes expertise in gearing technology, while the Leibniz Institute for Materials Engineering (IWT Bremen, FE 2) provides expertise in heat‑treatment technology. Within the framework of the project, extensive theoretical and experimental investigations will be conducted on test specimens and gears under systematic variation of microstructural grain‑size distributions, component size, shot‑peening condition, cleanliness level, and alloy composition.
The resulting findings will strengthen companies, particularly small and medium‑sized enterprises, by enabling them to utilize the load‑carrying potential of case‑hardened components more effectively. Furthermore, they will be able to independently quantify the effects of coarse grain using simple practical approaches and, if necessary, implement appropriate corrective measures to mitigate potential reductions in load‑carrying capacity. In production, this leads to a reduction of scrap and the associated repetition of energy‑intensive heat‑treatment and recycling processes. The anticipated project results will therefore contribute to improving the sustainability of manufacturing chains and products.