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Replication of specifically microstructured surfaces in A356-alloy via lost wax investment casting

: Ivanov, T.; Bührig-Polaczek, A.; Vroomen, U.; Hartmann, C.; Holtkamp, J.; Gillner, A.; Bobzin, K.; Bagcivan, N.; Theiß, S.


Journal of micromechanics and microengineering 21 (2011), No.8, Art. 085026, 10 pp.
ISSN: 0960-1317
ISSN: 1361-6439
Journal Article
Fraunhofer ILT ()

A common way of realizing microstructural features on metallic surfaces is to generate the designated pattern on each single part by means of microstructuring technologies such as e.g. laser ablation, electric discharge machining or micromilling. The disadvantage of these process chains is the limited productivity due to the additional processing of each part. The approach of this work is to replicate microstructured surfaces from a master pattern via lost wax investment casting in order to reach a higher productivity. We show that microholes of different sizes (Ø 15-22 µm at depths of 6-14 µm) can be replicated in AlSi7Mg-alloy from a laser-structured master pattern via investment casting. However, some loss of molding accuracy during the multi-stage molding process occurs. Approximately 50% of the original microfeature's heights are lost during the wax injection step. In the following process step of manufacturing a gypsum-bonded mold, a further loss in the surface quality of the microfeatures can be observed. In the final process step of casting the aluminum melt, the microfeatures are filled without any loss of molding accuracy and replicate the surface quality of the gypsum mold. The contact angle measurements of ultrapure water on the cast surfaces show a decrease in wettability on the microstructured regions (75°) compared to the unstructured region (60°).