Powder injection moulding of premixed ferritic and austenitic stainless steel powders

In this experimental work, powder injection moulding (PIM) of premixed 316L and 430L gas-atomized powders was developed to obtain duplex stainless steels. A multicomponent binder constituted of high density polyethylene (HDPE) and paraffin wax (PW) in a volume ratio 50/50 was selected for the process. Feedstocks with powder loadings of 50, 65, 68 and 70 vol.% were prepared. Mixing experiments were carried out at 170 °C according to differential scanning calorimetry (DSC) results. The rheological characterization of feedstocks allowed establishing different rheological parameters as power flow index (n) and activation energy (E_a) in order to know their suitability for injection moulding. Critical powder volume concentration (CPVC) was determined by means of oil absorption method and a rheological model. The feedstock was injected at 170 °C and three-point bending and tensile parts were obtained. Thermogravimetrical analysis (TGA) of binder allowed us to design the thermal debinding cycle and sintering was carried out in low vacuum at different temperatures. Finally, mechanical properties such as hardness and tensile strength were evaluated.