Fatigue Behaviour of Case-Hardened P/M Steels
Powder-metallurgical (P/M) produced components may be used as mass parts in a very large quantity. Due to the multistage manufacturing process which consists of the pressing of the prepared powder and the sintering of the green bodies also complex shaped components can be produced very economically and precisely. They can be utilised without any further post-processing if the whole production process is optimised. However, it is still difficult and only possible with considerable technical and financial effort to produce highly stressable components profitably using the sinter technique. Therefore, the examinations on hand had the intention to create the basis for the use of the sinter technology also for the production of highly stressable case-hardened components. To this, at first bending specimens were fabricated with modern pressing procedures and sinter facilities and first characterized in the as sintered state. Then the conditions for the case-hardening was analysed and the parameters for an optimised case-hardening procedure fixed. With these parameters specimens were case-hardened and their lifetime behaviour estimated under different bending loading conditions. Finally it should be checked whether the knowledge gained from the specimens could be applied to complex components. To this, gear wheels were produced using powder-metallurgy. The cyclical tooth foot strength of this gear wheels were analysed in the only sintered as well as in the case-hardened state. It could be demonstrated that the improvement of the fatigue strength of the bending specimens by case-hardening also appears at the tooth foot strength of the gear wheels.
S.W. Nam, Y.W. Chang, S.B. Lee and N.J. Kim
S. Seyedi et al., "Fatigue Behaviour of Case-Hardened P/M Steels", Key Engineering Materials, Vols. 345-346, pp. 371-374, 2007