Influence of injection variable on the density and properties of stainless steel injection molding parts

The quality of metal parts made by powder injection molding (MIM) method is influenced by a range of factors such as powder and binder characteristics, rheological behavior of feedstock, molding parameters and debinding and sintering conditions. In this study, to optimize the molding parameters, the effect of injection temperature and pressure on the properties of stainless steel in the MIM process were thoroughly studied. Experimental tests were conducted on 316L feedstock with 70 vol. powder. Injection molding was carried out at temperatures and pressures of 150-230 ◦C and 1300-1900 Bar respectively. Results showed that increase in injection temperature and pressure and the resulting increase in flow rate leads to the formation of void which impairs the properties of molded parts. The studies showed that injection at temperature of 100 °C results in evaporation of binder components. From the processing point of view, the temperature of 210 ˚C and pressure of 1900 Bar seems to be the most suitable condition for injection molding and result is high density. In addition, the effects of sintering conditions (temperature and time) on the microstructure are discussed. The best final properties were found using injection molding under the above stated conditions and sintering at 1380 ˚C during 3 h.

Keywords:

Metal Injection molding , injection temperature , 316L stainless steel , density