Development of Binder Jetting for highly stressed drive components by sintering according to requirements

• Applicants: Professor Dr.-Ing. Thomas Bergs; Professor Dr.-Ing. Christoph Broeckmann
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 496734156

Powder metal (PM) gears are porous and therefore not as strong as gears made from fully dense, melt-metallurgical material. The densification rolling process can increase the edge density up to 100% thereby strengthen the surface of PM gears, therefore in this way the load carrying capacity of the conventional 16MnCr5 gear steel can be thus matched or even exceeded. Porosity in the component core is accompanied by a reduction in weight and potential optimization of the operating behavior ("Noise Vibration Harshness"). Do to the special plant technology powder metallurgical production of gears using press forming and sintering is only economical in large batches or in series production. On the other hand, Binder Jetting (BJT) is a multi-stage, generative manufacturing process, which is mainly used for flexible prototype production. However, in the future, it can provide an economical solution to the conflicting demands of near-net-shape (NNS) production of gears in small batches.In BJT process, the green body is produced in layers by the selective deposition of binding material into the powder bed. In the subsequent debinding and sintering processes, the green body is converted to consolidated component. Final geometry, porosity and strength of BJT produced components are achieved after sintering. Therefore, material flexibility in BJT is only limited by the sinterability of the powder. Given the anisotropy of sinter shrinkage caused by the layered structure of the component in building direction, NNS production is only possible by balancing printing and sintering parameters. In comparison to the conventional economical production of high-performance gears of identical geometry in larger quantities, the development of the BJT process for the case-hardening steel powder 16MnCr5 is necessary, which is not suitable for conventional die pressing. Fundamental investigations of both the powder spreading process and the subsequent selective deposition of a liquid binding material are necessary to check the suitability of a material for BJT. The effect of these varying parameters on the sintering process as well as the resulted shrinkage and component profile deviation are to be analyzed by manufacturing test samples. Flat bar tension and vibration tests which are used to compare the tensile strength of the green body and the final component after sintering can provide information about the mechanical properties of the tested material. Only when the mechanical properties of the samples are confirmed to be good, the BJT process can be verified for manufacturing a gear prototype that would meet the requirements of the application.

• DFG Programme: Research Grants