High speed laser powder bed fusion of M789 tool steel with an optimized 120 µm layer thickness approach

Additive manufacturing (AM) of molds and tools is currently driven by the efficient design and rapid lead-time assured by the AM approach. However, current AM processes lack behind conventional manufacturing with respect to productivity rates and materials availability. The current study demonstrates the possibility of high speed laser powder bed fusion (LPBF) of a newly developed M789 maraging steel. Optimized parameters for 120 µm layer thickness (LT) fabrication are successfully determined to enable productivities >30 cm3/h. The effect on surface quality and defects occurrence is reported through profilometry and tomographic analyses. Furthermore, tensile properties are compared to the same M789 material produced with industrially certified 60 µm LT parameters. High relative density and acceptable mechanical properties are achieved by high speed LPBF of M789, thus facilitating the rapid-tooling of bulky geometries like complex mold assemblies. Albeit surface quality is severely deteriorated by the high-LT production, a hull-bulk method is established to counteract this effect, if so required.