Determination of fatigue lives and origin of crack initiation of steel piston alloys in the VHCF regime at elevated temperatures (T02*)

根据CRC920第一个资助期的子项目C04所获得的知识，本提案的目的是评估钢活塞合金在200°C至500°C至109次循环的应用相关温度范围内的疲劳性能。重点研究了材料生产条件(铸造和锻造合金)、化学成分、显微组织和缺陷(气孔、微缩孔、非金属夹杂物)等因素对铸件性能的影响。尤其是对损伤相关缺陷尺寸以及损伤累积的研究更是引起了人们的关注。预期的结果有助于阐明钢质活塞合金在高温下发生损伤的机理，并最终对活塞几何结构的改进设计做出贡献。此外，损伤相关夹杂物团聚的形成结果可以通过对过滤器支柱表面涂层的改性来提高在CRC920框架下开发的金属熔体过滤器的捕集能力。

Based on the knowledge gained in the subproject C04 during the first funding period of the CRC 920, the aim of the present proposal is to evaluate the fatigue properties of steel piston alloys in the application relevant temperature range between 200°C and 500°C up to 109 number of cycles. The investigations are focussed on the influence of materials production conditions (cast andwrought alloys), the chemical composition, the microstructure and defects like (pores, micro shrinkage cavities, non-metallic inclusions). Especially, investigations on the damage relevant defect size as well as damage accumulation are of great interest. The expected results can contribute to the clarification of occurring damage mechanisms in steel piston alloys at elevated temperatures and give finally a contribution to a modified design of piston geometries. Furthermore, results on the formation of damage relevant inclusion agglomerates can improve the entrapment capability of metal melt filters developed in the framework of the CRC 920 bymodification of the coating on the surface of filter struts.