OPTIMIZATION OF THE SINTERING PARAMETERS FOR MATERIAL MANUFACTURED BY POWDER INJECTION MOLDING

Abstract

The properties of sintered and heat-treated steels produced from the Catamold 8740 material by powder injection molding were studied. Parts made of the Catamold 8740 low-alloy mild carbon steel are used in the military, automotive, and other industries where high reliability and resistance to dynamic loads are required. The chemical homogeneity of the Catamold 8740 material was studied depending on the process parameters of powder injection molding: heating rate, sintering temperature, holding time, and subsequent heat treatment. Microscopic analysis showed that Catamold 8740 was a mechanical mixture of powders of various sizes (carbonyl iron, nickel, Fe–Mo, Fe–Cr, Fe–Si-Mo, Fe–Si). When the heating rate of the Catamold 8740 powder mixture increases from 2 to 5 °C/min, the microstructural heterogeneity decreases due to locally inhomogeneous compaction and the alloy formation is activated at 900–1340 °C. The impact strength of the V-notch parts measured by the Charpy method rises from 10.39 to 11.52 J/cm² with increase in the sintering temperature and heating rate from 2 °C/min (1270 °C) to 5 °C/min (1340 °C). At a sintering temperature of 1340 °C, an increase in the holding time from 30 to 90 min raises the density of the material, promotes rounding of the pores, and homogenizes the ferrite matrix. However, the impact strength of the products decreases by a factor of 1.4, which is associated with coarser grain size and brittle fracture. Heat treatment processes reduce the impact strength. The results obtained were used to optimize the parameters of powder sintering by injection molding. The influence of chemical and dimensional inhomogeneity of the starting Catamold 8740 powders and sintering kinetics on the structure and mechanical properties of parts operating under impact loads was established.