Investigating of Mixture Ratio of 925 Sterling Silver Compound for the Metal Injection Molding Process

Abstract

The objective of this study is to determine the mixture ratio of 925 sterling silver compound that was
feasible to produce complete green part via a metal injection molding process. The mixture ratios of 925
sterling silver powder to the binder mixture were varied. The particle sizes of 925 sterling silver powders were
100 µm and less. The binder mixture consisted of high density polyethylene, polyvinyl alcohol, polyethylene
glycol, paraffin wax as plastic flow ability promoting agent and stearic acid as lubricant. All mixtures were then
mixed with an internal mixer. Metal injection molding was performed by using a ram injection machine under
constant pressure and temperature of 190 ºC and150 bars, respectively. The highest ratio of 925 sterling silver
powder to the binder mixture that could inject the complete parts was required. The results exhibited that
the favorable green parts were achieved by the formula with the mixture ratio of 90 percent of 925 sterling
silver powder to10 percent of binders by weight. The components of the formula included 120 grams of 925
sterling silver powder and 13.33 grams of binders, containing 5.067 grams of high density polyethylene, 0.500
grams of polyvinyl alcohol, 0.167 grams of polyethylene glycol, 7.200 grams of paraffin wax and 0.400 grams
of stearic acid. The green parts of the formula had average green density of 4.507 g/cm3
and average green
strength of 17.70 MPa. This mixture ratio can be utilized in the metal injection molding for producing the
green parts.