Einsatzgehärtete Sinterstähle

FKM 2005
Issue no. 288
Project no. 245

Final report
Abstract:

Components produced by powder metallurgy (PM) are used today in very large quantities, especially as mass-produced parts. The multi-stage manufacturing process, which essentially consists of pressing the prepared powder and sintering, means that, with optimized process control, even complex components can be produced in large quantities at very low cost and with such precision that they can be used without further post-processing. Due to the manufacturing process, powder metallurgical components are significantly inferior to components made from semi-finished products produced by melting metallurgy. Although considerable progress has been made recently through improved starting powders, optimized manufacturing conditions and new pressing and sintering processes such as hot pressing and high-temperature sintering, it is still difficult and only possible to produce highly stressable components by sintering at considerable technical and financial expense. The aim of this research project was therefore to establish a scientific basis for the use of sintering technology in the manufacture of highly stressed components. The PM steels Fe1.5Mo2Cu+O,25%C, Fe3CrO,5Mo+O,30%C and Fe4Ni1.5CuO,5Mo+O,25%C were selected for this purpose. Initially, bending samples of these materials were produced using state-of-the-art pressing methods and sintering furnaces and characterized in the sintered state only. In the following sections of the study, the boundary conditions for case hardening of the samples were then investigated, the parameters for optimized case hardening of the respective materials were determined and finally samples of the respective test materials were case hardened with these parameters. These samples were used to determine the service life behavior of the case-hardened conditions of the test materials under bending stress. In the final stage of the research project, it was then examined whether and with which evaluation method the findings obtained from the samples could be transferred to complex components. For this purpose, gears were produced from the test materials by powder metallurgy, which exhibited similar microstructural conditions in the tooth root area as the bending samples. The cyclic tooth root strength of these gears in sintered and case-hardened condition was analyzed. By determining the tooth root stress according to DIN 3990, it was possible to transfer the fatigue strength parameters of the bending specimens to the test gears. The objective of the research project was thus achieved. 122 p., 161 ill., 24 tab., 89 lit. Start of work:
01.07.2000 End of work:
31.05.2005 Funding body:
AVIF-No. A144 Research center:
Institute for Materials Science I (IWK I) of the University of Karlsruhe TH), Karlsruhe Prof. Dr.-lng. D. Löhe Project management:
Dr.-Ing.K.-H.Lang Processor and author:
Dipl.-Ing. S.Seyedi Chairman of the working group:
Dr.rer.nat H.P.Koch,Robert Bosch Gm bH Chairman of the advisory board:
Dr.Ing. E,h.J. Rabe, Höchstadt