Additive manufacturing of high temperature metallic materials
For increasing the thermodynamic efficiency of gas turbines two different approaches with respect to the selection of materials are of importance. Firstly, using high temperature materials beyond the potential of currently used nickelbased superalloys will result in an increase of efficiency, since the maximum process temperature depends on the capability of the used materials. Secondly, lightweight materials providing similar mechanical properties compared to the conventional materials benefit due to the obtained mass reduction. Mo-Si-B alloys with its ultra-high melting point and Vi-S-B alloys with its density-reducing effect on the contrary follow the approaches described above and are under focus of the current research since both provide promising high temperature capabilities. However, ingot processing (IM) of this class of materials is challenging due to the high melting points and different multi-step powder metallurgical processes (PM) were typically used in the past to produce dense samples out of this class of material. This work shows the feasibility of printing pre-alloyed near-eutectic Mo-Si-B and V-Si-B powder materials via directed energy deposition (DED) as a method for AM. Therefore, Mo-Si-B and V-Si-B powder was manufactured via gas atomization (GA) process out of solid raw materials meeting the requirements for AM regarding flowability and particle size. The specific challenge is the ultra-high melting point of this type of alloys, accompanied by problems of interlayer bonding and defects that may occur during cooling. Compact specimens having a microstructure of primary solidified solid solution phases next to eutectic regions could be manufactured. For further understanding of the microstructural evolution of the powder particles after GA were investigated and a detailed analyses of the resulting microstructures were carried out. For purpose of comparison with other Mo-Si-B/V-Si-B alloys and classification of the competitiveness first results of the mechanical testing are presented.