Fabrication of Injection Moulded 304L Stainless Steels Reinforced with Tungsten Carbide Particles

Abstract

Powder injection moulding of 304L stainless steel - tungsten carbide (WC) composites were carried out in the present work. Two different WC particle i.e. WC having average size of 4.8 µm and 1.6 µm were used. Feedstock of powder loading up to 55 vol% were successfully prepared using binder composed mainly of polyethylene glycol (PEG) and a minor constituent of polymethylmethacrylate (PMMA). The mouldings were leached in water at temperatures of 40 °C and 60 °C from 30 minutes to 24 hours in order to study the effect of leaching conditions on the removal of the PEG. The remaining binder, PMMA, provided strength to the mouldings after leaching of the PEG and it could be removed by pyrolysis during ramping up to the sintering temperature. Specimens were sintered under hydrogen atmosphere at 1250 °C for 1 hour. Sintered components were subjected to testing and characterisation. Scanning electron microscope was used to observe microstructure of specimens after moulding, leaching and sintering. It was found that the hardness of the sintered specimens increased with either increasing the amount of the powder loading in the feedstock or reducing the average size of WC in the powder mixture. In addition, the water leaching of the PEG linearly correlates with the natural log of time and the equation predicts that PEG will be removed completely in 11.24 ± 1.31 hours which corresponds with the experiment result that PEG completely removed in 12 hours.