IMPROVED DIMENSIONAL STABILITY OF SINTER HARDENING POWDERS THROUGH OPTIMIZED MIX FORMULATION AND ADDITIVES SELECTION

摘要

The use of sinter hardening steel powders in furnaces equipped with fast cooling units is a cost effective process for the production of parts with high strength and apparent hardness without secondary heat treatment. However, the high hardness achieved after sintering does not allow for sizing and machining is very difficult. Therefore, the factors affecting the dimensional variation of parts during sintering must be very well understood and carefully controlled in order to achieve precise final dimensions. The behavior of sinter hardening powders during sintering was characterized by dilatometry. The effects of sintering temperature and time as well as powder mix formulation on the final dimensions are discussed. Particular attention is paid to the influence of carbon diffusion from the graphite on the final part dimension. The performance of a new grade of graphite specifically developed to ensure greater dimensional stability is presented. The improved dimensional stability of various powder mix formulations containing that grade of graphite is discussed.