R. Bernhard
P. Neef
H. Wiche
V. Wesling
C. Hoff
J. Hermsdorf
S. Kaierle

Additive manufacturing of coppermolybdenum pseudoalloys

SPIE Proceedings Vol. 11349: 3D Printed Optics and Additive Photonic Manufacturing
Type: Zeitschriftenaufsatz (non-reviewed)
The joint project GROTESK investigates the application of additive manufacturing for the generation of optical, thermal and structural components using the example of a laser system. This includes multi-material connections of metallic and non-metallic materials with laser metal deposition, e.g. mountings for solid-state laser materials like neodymium-doped yttrium aluminum garnet (Nd:YAG), and the related material development for wire-based as well as powder-based processing. The contrary material groups require an exact consideration of the thermal and physical properties. In particular, the melting point of the alloy must be as low as possible, preventing thermal destruction of the Nd:YAG. Furthermore, this reduces the thermal gradient in the crystalline structure of the YAG and improves thermal shock resistance. Besides, a sufficient thermal conductivity is important to ensure a targeted heat dissipation. Another crucial aspect is the induced stress due to different thermal expansions of the connected materials leading to structural damage. Therefore, the thermal expansion coefficient of the alloy has to match the coefficient of the optical component. The recent approach is the application of copper-molybdenum pseudoalloys. The idea is to combine the low thermal expansion of molybdenum with the high thermal conductivity of copper. State-of-the-art are sintered molybdenum powders that are infiltrated with molten copper resulting in promising physical properties exceeding the requirements of the intended purpose and allowing the application in high-power laser systems. During first practical experiments with these powders, promising results have been achieved with a 680-Watt diode laser by solely melting the copper. The structure of the generated object contained unaffected molybdenum grains embedded into a copper matrix and therefore successfully forming a pseudoalloy. Effects of the adjusted powder composition, the laser parameters and the resulting thermomechanical properties are investigated. With the help of microsections, the additive manufactured pseudoalloys are evaluated and characterized.