Investigation of Laser-Material Interactions of Functionalized Diamond-Impregnated Metal Matrix Composite Formulations During Laser Powder Bed Fusion

• Applicants: Dr.-Ing. Stefan Kleszczynski; Professor Dr.-Ing. Wolfgang Tillmann
• Subject Area: Materials in Sintering Processes and Generative Manufacturing Processes ; Synthesis and Properties of Functional Materials
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 445942492

The objective of the project is to generate a fundamental understanding of the interactions that occur during the melting and solidification of diamond-reinforced metal matrix composites (DMMC) during the laser powder bed fusion (PBF-LB/M) process. In the approach pursued here, DMMCs are produced from a mixture of diamonds and steel powder (1.4404). Since diamonds graphitize at approx. 720°C, arc PVD coatings are applied to the diamond particles and the influence of laser exposure on graphitization is investigated. The metallic coatings are also used to induce carbidic interfacial reactions between the diamonds and the metallic matrix, creating strong bonds on the one hand and a diffusion barrier on the other. In the first funding phase, mixtures of stainless steel powder and coated diamond particles were successfully processed in the PBF-LB/M process. With the help of pyrometry and high-speed imaging, the thermal cycles during melting and the resulting melt pool characteristics were characterized and, supported by a thermal simulation of the additive manufacturing process, a significant improvement in the mechanical property profile of the DMMC materials produced was achieved. In some cases, graphitization effects and cracking caused by agglomerated diamond particles are still visible within the test specimen. In the second funding phase, this problem is to be addressed by a thermal-fluid-dynamic simulative description of the melting process. In particular, the particle migration of the diamonds in the melt pool is to be mapped and validated by experimental analyses. The latter will be implemented using extended high-speed videography in combination with the methodology already developed for in-situ pyrometry. The material characterization of the manufactured DMMCs focuses primarily on the analysis of the interparticle cohesive force of the coated diamonds, the holding force coefficient, the bending strength, and the structural integration and integrity of the diamonds within the metal matrix. Based on the results, conclusions are drawn about the interaction between the material, the resulting process behavior, and the microstructural properties and used to derive a process strategy for the production of defined graded DMMC components.

• DFG Programme: Research Grants
• Co-Investigators: Professor Dr.-Ing. Wojciech Kowalczyk; Dr.-Ing. Jan Wegner