Microstructure of Non-Metallic Inclusions Identified in Cast Steel 42CrMo4 after Metal Melt Filtration by Novel Foam Filters

摘要

Non-metallic inclusions can affect significantly the mechanical properties of metallic materials. Mainly for safety relevant components, it is important to reduce size and number of non-metallic inclusions. Recent research work is focused on the development of new reactive, active, and functionalized filters for the reduction of non-metallic inclusions. A detailed knowledge on the genesis of inclusions is essential to improve the entrapment capability. The paper is focused on the microstructure of inclusions formed in cast steel 42CrMo4 after the application of two filter variants. Both, inclusions on the filter surface as well as inclusions in the as-cast steel are investigated using scanning electron microscopy. Their chemical composition and their crystal structure are identified by combined EBSD and EDS measurements. The three-dimensional morphology of the inclusions is analyzed by deep etching technique as well. Finally, the clusters and agglomerates exhibit a quite complex microstructure. Thus, the majority of inclusion clusters consists of alumina, spinel, mullite, MnS, and TiOx. This agrees well to the scenario of the evolution of inclusions described in the literature.