High-strength gears produced by powder metallurgical processes

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For manufacturing of gears several process chains can be applied. A process chain with high resource efficiency is a powder metallurgical production, which is composed by die pressing, sintering, densification rolling and case hardening. Manufacturing resource employment is minimized by energy efficient manufacturing and low material usage. Surface densified PM gears with a comparable strength have a 10% reduced weight compared to fully dense gears. This also contributes to resource efficiency.The proposed research project targets an improved material usage and a load suitable boundary layer for optimization of part design. Hence the project directly addresses the objectives of the Priority Program Resource efficient machine elements (SPP 1551)The objective of this project is the increase of resource efficiency of gears by a holistic optimization of the powder metallurgical gear production. For that an optimization of tooth root geometry and surface density profile by prediction of tooth root strength will be performed. Therefore, different density profiles are considered for the determination of the optimal tooth root geometry and the prediction of its strength. For the latter, the methodology developed in phase 1 is used. By comparison of experiment and theoretically determined values the methodology to predict tooth root endurance strength is verified. Furthermore, the potential of variable tooth geometries for powder metallurgical manufactured, surface densified gears is evaluated. It will be investigated, which tooth geometries are suitable for surface densification by rolling. Furthermore, the potential of shot peening as an alternative densification process is evaluated. Shot peening offers the possibility to densify geometries, which are not rollable. Additionally, the methodology to predict tooth root endurance strength is extended to predict the rolling strength as well. The local comparison of load and strength will be extended to Hertzian contact for a material with profile of density and carbon content.The cooperation within Priority Program Resource efficient machine elements (SPP 1551) will be used to apply chosen methods of other projects to generate boundary layers onto the process chain to produce PM gears. Suitable processes for generating boundary layers are to be identified and investigated. This shall result in a further increase of resource efficiency during the gears usage. Comparison of strength and process chains will result in a verification of resource efficiency.