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Transfer case sprockets usually require quenching to improve hardness and mechanical properties. This additional process step can be avoided with sinter hardening. Indeed, sinter hardening allows the production of P/M parts with high strength and apparent hardness directly from sintering because the martensitic transformation takes place during the cooling portion of the sintering operation. Therefore, this process eliminates the need for a post-sintering heat treatment with all the inherent related problems such as part distortion, oil contamination and added processing costs. Many low alloy steel powders have been developed for sinter hardening applications. These materials, combined with the availability of sintering furnaces equipped with enhanced cooling capacity, make sinter hardening particularly attractive for parts that are difficult to quench because of their size and shape.

The influence of sintering parameters on mechanical properties of three different sinterhardenable grades of powder has been studied. Dimensional change, hardness, strength, and microstructure of specimens were evaluated in different sintering conditions, such as temperature, belt speed, and cooling rate. Conclusions were used to convert a major line of sprockets from a traditional mold, sinter, size, and quench process to a cost effective mold and sinterhard one. Mechanical tests, such as crush tests and engine tests were performed on real parts manufactured using both processes, confirming the validity and the benefits of this conversion.